Initiation of Marijuana Use:

Trends, Patterns, and Implications

Joseph C. Gfroerer

Li-Tzy Wu

Michael A. Penne

DEPARTMENT OF HEALTH AND HUMAN SERVICES

Substance Abuse and Mental Health Services Administration

Office of Applied Studies
ii

Acknowledgments

This report was prepared by the Division of Population Surveys, Office of Applied Studies (OAS),

Substance Abuse and Mental Health Services Administration (SAMHSA), and by RTI of Research

Triangle Park, North Carolina, under Contract Nos. 283-98-9008 and 283-99-9018. At SAMHSA, Joseph

C. Gfroerer coauthored the report and reviewed its progress. At RTI, Li-Tzy Wu was the major

contributor to the report and was task leader for its production. Yvonne U. Ohadike assisted in the

preparation of the literature review; Michael A. Penne was statistician for the report and Weihua Shi

provided statistical analyses; Ralph E. Folsom, Akhil K. Vaish, Neeraja S. Sathe, and Lea T. Drye

conducted the small area estimation; and David Chrest and Shari B. Lambert developed the State maps.

Mary Ellen Marsden reviewed the report, Richard S. Straw and David Belton edited it, and Pamela Couch

Prevatt and Teresa F. Gurley prepared its web versions.

Public Domain Notice

All material appearing in this report is in the public domain and may be reproduced or copied without

permission from the Substance Abuse and Mental Health Services Administration. However, this

publication may not be reproduced or distributed without the specific, written authorization of the Office

of Communications, SAMHSA, U.S. Department of Health and Human Services. Citation of the source is

appreciated. Suggested citation:

Gfroerer, J. C., Wu, L.-T., & Penne, M. A. (2002). Initiation of Marijuana Use: Trends,

Patterns, and Implications (Analytic Series: A-17, DHHS Publication No. SMA

02-3711). Rockville, MD: Substance Abuse and Mental Health Services Administration,

Office of Applied Studies.

Obtaining Additional Copies of Publication

Copies may be obtained, free of charge, from the National Clearinghouse for Alcohol and Drug

Information (NCADI), a service of SAMHSA. Write or call NCADI at:

National Clearinghouse for Alcohol and Drug Information

P.O. Box 2345, Rockville, MD 20847-2345

(301) 468-2600, 1-800-729-6686, TDD 1-800-487-4889

Electronic Access to Publication

This publication can be accessed electronically through World Wide Web connections:

http://www.samhsa.gov

http://www.DrugAbuseStatistics.SAMHSA.gov

Originating Office

SAMHSA, OAS

5600 Fishers Lane, Room 16-105

Rockville, MD 20857

July 2002
iii

Table of Contents

Chapter Page

List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v

List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1. Introduction ............................................................3

1.1 Purpose of the Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Background on Marijuana Use and Initiation of Marijuana Use ..............4

1.2.1 Recent Trends in Use .........................................4

1.2.2 Prior Studies of Marijuana Initiation .............................5

1.2.3 Research on Seasonality of Substance Use ........................5

1.2.4 Predictors of Initiation ........................................6

1.2.5 Sequencing of Substance Use Initiation ..........................6

1.2.6 Early Marijuana Use and Later Substance Use Problems .............7

2. Data and Methods .......................................................9

2.1 Data Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

2.2 Limitations of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.3 Analysis Sample . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.4 Measures and Definitions of the Terms Used in the Report . . . . . . . . . . . . . . . . 13

2.4.1 First Marijuana Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.4.2 Social and Demographic Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

2.4.3 Use of Cigarettes, Alcohol, and Other Drugs . . . . . . . . . . . . . . . . . . . . . 14

2.4.4 Heavy Use of Illicit Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

2.4.5 Dependence on or Abuse of Alcohol and Other Drugs . . . . . . . . . . . . . . 15

2.5 Statistical Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.1 Incidence Estimation: National . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.2 Incidence Estimation: State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.5.3 Logistic Regression Analyses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3. Trends in Marijuana Incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.2 Trends in Marijuana Incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.3 Trends, by Age and Gender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.4 Trends, by Race/Ethnicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

4. State Incidence Estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

4.2 State-Level Estimates of Recent New Marijuana Users . . . . . . . . . . . . . . . . . . . 35
Table of Contents (continued)

Chapter Page

iv

5. Characteristics of Recent Marijuana Initiates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.1 Prior Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

5.2 Characteristics of Recent Marijuana Initiates . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

5.3 Seasonality of Incidence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

5.4 Logistic Regression Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5.4.1 Results for Persons Aged 12 to 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.4.2 Results for Persons Aged 12 to 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

5.4.3 Results for Persons Aged 15 to 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.4.4 Results for Persons Aged 18 to 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

5.4.5 Results for Persons Aged 21 to 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

6. Early Marijuana Use and Later Drug Use Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.2 Estimated Prevalence of Illicit Drug Use, Heavy Illicit Drug Use, Substance

Abuse, and Dependence, by Age of Marijuana Initiation . . . . . . . . . . . . . . . . . . 62

6.2.1 Use of Heroin, Cocaine, and Psychotherapeutics Nonmedically . . . . . . 62

6.2.2 Heavy Illicit Drug Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.2.3 Substance Dependence and/or Abuse . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

6.3 Multiple Logistic Regression Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

6.3.1 Adjusted Odds Ratios of Use of Heroin, Cocaine, and 

Psychotherapeutics Nonmedically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

6.3.2 Adjusted Odds Ratios of Heavy Illicit Drug Use . . . . . . . . . . . . . . . . . . 67

6.3.3 Adjusted Odds Ratios of Substance Dependence and/or Abuse . . . . . . . 67

6.4 Substance Dependence and/or Abuse Among Past Year Marijuana Users . . . . . 68

6.4.1 Estimated Prevalence of Illicit Drug Dependence and/or Abuse, by 

Age of Marijuana Initiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

6.4.2 Adjusted Odds Ratios of Substance Dependence and/or Abuse . . . . . . . 69

7. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Appendix

A Statistical Methods and Limitations of the Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

B Selected Standard Error Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

C Selected Questionnaire Pages (1999 and 2000 NHSDAs) . . . . . . . . . . . . . . . . . . . . . . 133
v

List of Figures

Figure Page

3.1 Marijuana Incidence Rates, by Year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.2 Marijuana Incidence Rates, by Gender and Year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.3 Marijuana Incidence Rates, by Race/Ethnicity and Year . . . . . . . . . . . . . . . . . . . . . . . . 26

4.1 Average Annual Incidence of Marijuana Use among Persons Aged 12 or Older: 

1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.2 Average Annual Incidence of Marijuana Use among Youths Aged 12 to 17: 

1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

4.3 Average Annual Incidence of Marijuana Use among Young Adults Aged 18 to 25: 

1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.1 Recent Marijuana Initiates, by Age at First Use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

5.2 Prior Alcohol and Cigarette Use among Recent Marijuana Initiates, by Gender . . . . . . 49

5.3 Estimated Average Number of Marijuana Initiates Per Day for Each Month: Overall 

and by Gender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

6.1 Prevalence of Lifetime Use of Heroin, Cocaine, and Psychotherapeutics among 

Adults Aged 26 or Older, by Age of Marijuana Initiation: 1999 and 2000 . . . . . . . . . . . 63

6.2 Prevalence of Past Year Heavy Marijuana Use and Heavy Use of Other Illicit Drugs

among Adults Aged 26 or Older, by Age of Marijuana Initiation: 1999 and 2000 . . . . . 64

6.3 Prevalence of Past Year Alcohol and/or Illicit Drug Dependence or Abuse among 

Adults Aged 26 or Older, by Age of Marijuana Initiation: 2000 . . . . . . . . . . . . . . . . . . 65
vi

List of Tables

Table Page

2.1 Survey Sample Sizes for All Respondents Aged 12 or Older, by Age Group and

Demographic Characteristics: 1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.2 Survey Sample Sizes for All Respondents Aged 12 or Older, by Age Group and

Geographic Characteristics: 1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.1 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana During 

the Years 1965 to 1999, Their Mean Age at First Use, and the Annual Incidence 

Rates of First Use (Per 1,000 Person-Years of Exposure), for All Ages . . . . . . . . . . . 28

3.2 Estimated Age-Gender Numbers (in Thousands) of Persons Who First Used 

Marijuana During the Years 1965 to 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

3.3 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana During 

the Years 1965 to 1999, Their Mean Age at First Use, and the Annual Incidence 

Rates of First Use (Per 1,000 Person-Years of Exposure), by Gender . . . . . . . . . . . . . 30

3.4 Estimated Annual Age-Gender Specific Incidence Rates of First Use (Per 1,000

Person-Years of Exposure) of Persons Who First Used Marijuana During the 

Years 1965 to 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.5 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana During 

the Years 1965 to 1999, by Racial/Ethnic Subgroups . . . . . . . . . . . . . . . . . . . . . . . . . 32

3.6 Estimated Mean Ages at First Use of Persons Who First Used Marijuana During 

the Years 1965 to 1999, by Racial/Ethnic Subgroups . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.7 Estimated Annual Incidence Rates of First Use (Per 1,000 Person-Years of 

Exposure) of Persons Who First Used Marijuana During the Years 1965 to 1999, 

by Racial/Ethnic Subgroups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.1 Estimated Numbers (in Thousands) of Average Annual Marijuana Initiates, by 

Age Group and State: 1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

4.2 Average Annual Rates of First Use of Marijuana, by Age Group and State: 

1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5.1 Characteristics of Recent Marijuana Initiates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

5.2 Prior Alcohol and Cigarette Use among Recent Marijuana Initiates . . . . . . . . . . . . . 54
List of Tables (continued)

Table Page

vii

5.3 Distribution of Month of First Marijuana Use among Persons Aged 12 or Older . . . . 55

5.4 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons 

Aged 12 to 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

5.5 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons 

Aged 12 to 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.6 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons 

Aged 15 to 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

5.7 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons 

Aged 18 to 20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

5.8 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons 

Aged 21 to 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

6.1 Percentages with Lifetime and Past Year Use of Heroin, Cocaine, and 

Psychotherapeutics among Adults Aged 26 or Older, by Age at First Marijuana 

Use and Age Groups: 1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

6.2 Percentages with Past Year Heavy Marijuana Use and Heavy Use of Other Illicit

Drugs among Adults Aged 26 or Older, by Age at First Marijuana Use and Age

Groups: 1999 and 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

6.3 Percentages with Past Year Alcohol and/or Illicit Drug Dependence or Abuse 

among Adults Aged 26 or Older, by Age at First Marijuana Use and Age Groups: 

2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

6.4 Adjusted Odds Ratios of Lifetime Use of Heroin, Cocaine, and Psychotherapeutics

among Lifetime Marijuana Users Aged 26 or Older: 1999 and 2000 . . . . . . . . . . . . . 74

6.5 Adjusted Odds Ratios of Past Year Use of Heroin, Cocaine, and Psychotherapeutics

among Lifetime Marijuana Users Aged 26 or Older: 1999 and 2000 . . . . . . . . . . . . . 75

6.6 Adjusted Odds Ratios of Past Year Heavy Marijuana Use and Heavy Use of Other 

Illicit Drugs among Lifetime Marijuana Users Aged 26 or Older: 1999 and 2000 . . . 76

6.7 Adjusted Odds Ratios of Past Year Illicit Drug Dependence or Abuse and Alcohol or

Illicit Drug Dependence or Abuse among Lifetime Marijuana Users Aged 26 or 

Older: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
List of Tables (continued)

Table Page

viii

6.8 Adjusted Odds Ratios of Past Year Alcohol Dependence and Illicit Drug 

Dependence among Lifetime Marijuana Users Aged 26 or Older: 2000 . . . . . . . . . . . 78

6.9 Adjusted Odds Ratios of Past Year Marijuana Dependence and Other Illicit Drug

Dependence among Lifetime Marijuana Users Aged 26 or Older: 2000 . . . . . . . . . . . 79

6.10 Percentages with Past Year Alcohol and/or Illicit Drug Dependence or Abuse 

among Past Year Marijuana Users Aged 26 or Older, by Age at First Marijuana 

Use: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

6.11 Adjusted Odds Ratios of Illicit Drug Dependence or Abuse and Alcohol or Illicit 

Drug Dependence or Abuse among Lifetime Marijuana Users Aged 26 or Older 

Who Also Used Marijuana in the Past Year: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

6.12 Adjusted Odds Ratios of Past Year Alcohol Dependence and Illicit Drug 

Dependence among Lifetime Marijuana Users Aged 26 or Older Who Also Used

Marijuana in the Past Year: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

6.13 Adjusted Odds Ratios of Past Year Marijuana Dependence and Other Illicit Drug

Dependence among Lifetime Marijuana Users Aged 26 or Older Who Also Used

Marijuana in the Past Year: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

A.1 Summary of 2000 NHSDA Suppression Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

A.2 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by 

Screening Result Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

A.3 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Persons Aged 12 or Older . . . . . . . . . . . . . . . . . . . . . . . . . . 113

A.4 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Youths Aged 12 to 17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

A.5 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Persons Aged 18 or Older . . . . . . . . . . . . . . . . . . . . . . . . . . 114

A.6 Response Rates and Sample Sizes for the 1999 and 2000 NHSDAs, by 

Demographic Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

A.7 Comparison of Initiation Rates, by Year of Initiation and Survey Year . . . . . . . . . . 116

A.8 Marijuana Annual Age-Specific Rates at First Use Per 1,000 Person-Years of

Exposure: 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
List of Tables (continued)

Table Page

ix

A.9 Comparison of Numbers of Marijuana Initiates (in Thousands) and Mean Age at 

First Marijuana Use: 1994-1998 PAPI Versus 1999 CAI . . . . . . . . . . . . . . . . . . . . . 118

A.10 Comparison of Mode Effect: Marijuana Annual Age-Specific Rates at First Use 

Per 1,000 Person-Years of Exposure with PAPI and CAI Data . . . . . . . . . . . . . . . . . 119

3.1S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First Used

Marijuana During the Years 1965 to 1999, Their Mean Age at First Use, and the

Annual Incidence Rates of First Use (Per 1,000 Person-Years of Exposure), for 

All Ages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

3.2S Standard Errors of Estimated Age-Gender Numbers (in Thousands) of Persons 

Who First Used Marijuana During the Years 1965 to 1999 . . . . . . . . . . . . . . . . . . . . 124

3.3S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First Used

Marijuana During the Years 1965 to 1999, Their Mean Age at First Use, and the

Annual Incidence Rates of First Use (Per 1,000 Person-Years of Exposure), by 

Gender . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

3.4S Standard Errors of Estimated Annual Age-Gender Specific Incidence Rates of First 

Use (Per 1,000 Person-Years of Exposure) of Persons Who First Used Marijuana

During the Years 1965 to 1999 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

3.5S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First Used

Marijuana During the Years 1965 to 1999, by Racial/Ethnic Subgroups . . . . . . . . . 127

3.6S Standard Errors of Estimated Mean Ages at First Use of Persons Who First Used

Marijuana During the Years 1965 to 1999, by Racial/Ethnic Subgroups . . . . . . . . . 128

3.7S Standard Errors of Estimated Annual Incidence Rates of First Use (Per 1,000 

Person-Years of Exposure) of Persons Who First Used Marijuana During the 

Years 1965 to 1999, by Racial/Ethnic Subgroups . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

6.1S Standard Errors and Suppression Rule for Percentages with Lifetime and Past Year 

Use of Heroin, Cocaine, and Psychotherapeutics among Adults Aged 26 or 

Older, by Age at First Marijuana Use and Age Groups: 1999 and 2000 . . . . . . . . . . 130

6.2S Standard Errors and Suppression Rule for Percentages with Past Year Heavy

Marijuana Use and Heavy Use of Other Illicit Drugs among Adults Aged 26 or 

Older, by Age at First Marijuana Use and Age Groups: 1999 and 2000 . . . . . . . . . . 131
List of Tables (continued)

Table Page

x

6.3S Standard Errors and Suppression Rule for Percentages with Past Year Alcohol 

and/or Illicit Drug Dependence or Abuse among Adults Aged 26 or Older, by 

Age at First Marijuana Use and Age Groups: 2000 . . . . . . . . . . . . . . . . . . . . . . . . . . 132
1

Highlights

Estimates of first-time drug use, referred to as incidence or initiation, provide an

important measure of the Nation's drug use problem. They suggest emerging patterns of use and

identify periods of heightened risk for an immediate focus on the prevention of substance use,

particularly among children and youths. Incidence data also suggest the future burden on

substance abuse treatment systems. This report contains an analysis of the initiation of marijuana

use. Marijuana is the most widely used illicit drug in the United States and is, in most cases, the

first illicit drug used by persons who have used an illicit drug. The analysis is based on data from

the 1999 and 2000 National Household Surveys on Drug Abuse (NHSDAs). Selected findings

are given below:

! An estimated 2.0 million Americans aged 12 or older used marijuana for

the first time in 1999. This was fewer than the estimated number of new

users in 1998 (approximately 2.5 million Americans), but still above the

1989 and 1990 levels (1.4 million each year). 

! The rate of marijuana initiation increased during the late 1960s and early

1970s, with a peak in 1976 and 1977 (21.0 per 1,000 potential new users).

After that period, the rate of new marijuana use decreased to 8.5 in 1990,

followed by an increase to 16.8 in 1996, then a decrease to 13.6 in 1999. 

! The trend in marijuana incidence since 1965 followed the same general

pattern for males and females, although rates for females were

consistently below rates for males. In 1999, the rates of new use per 1,000

potential new users were 15.5 for males and 12.1 for females. 

! The rates of first marijuana use among American Indians/Alaska Natives

were higher than for other racial/ethnic groups during the 1990s. Unlike

the overall trend in rates, which showed a peak in 1996, the trend for

American Indians/Alaska Natives indicated a continuing increase,

reaching 46.5 per 1,000 potential new users in 1999.

! The mean age at first marijuana use was 19 years in the early 1970s and

decreased to 17 years in the 1990s. The trends for males and females were

parallel, with males initiating at an earlier age than females, on average. 

The average age of new marijuana users in 1999 was 16.4 years for males

and 17.6 years for females.

! These average annual incidence rates varied slightly across different

States and age groups. Colorado, Delaware, Massachusetts, New

Hampshire, and Vermont were ranked in the top 10 for the overall age

group (ages 12 or older), the youth age group (ages 12 to 17), and the

young adult age group (ages 18 to 25). New Mexico had the highest rate
2

for the overall and youth age groups. Minnesota had the highest rate for

the overall and young adult age groups. By comparison, Louisiana had the

lowest rate of recent new users for the overall, youth, and young adult age

groups. Texas and Utah had the lowest rates of recent initiation among

youths and young adults.

! Among recent initiates of marijuana (first use in 1998 or 1999), nearly

three quarters had first used between the ages of 13 and 18. More than a

quarter initiated use at age 14 or younger.

! Approximately 60 percent of recent initiates had used both alcohol and

cigarettes prior to their first use of marijuana. About 9 percent had never

used alcohol or cigarettes at the time of first marijuana use, and the

remaining recent initiates had used either alcohol only (16.6 percent) or

cigarettes only (14.8 percent).

! The average number of marijuana initiates per day during 1998 and 1999

was highest in June and July. For females, the months with the highest

rates of initiation were January and July. On average during 1998 and

1999, there were 3,197 male initiates and 2,989 female initiates per day.

Among males, the number of daily initiates increased to approximately

4,300 in June and July. Among females, the estimated initiates per day

rose to 3,625 in July and 3,519 in January.

! Prior use of alcohol or cigarettes was highly correlated with becoming a

new marijuana user. Among persons aged 12 to 25 who had never used

marijuana, those who had smoked cigarettes were an estimated 6 times

more likely than nonsmokers to initiate marijuana use within 1 year.

Alcohol users were an estimated 7 to 9 times more likely than nonusers to

start using marijuana within a year. Daily cigarette smoking was

associated with a twofold increase in risk for marijuana initiation.

! Initiation of marijuana use before age 15 was associated with a greater risk

of other drug use behaviors at age 26 or older. These behaviors include

heroin use, cocaine use, nonmedical psychotherapeutic use, daily or

almost daily marijuana use, and weekly use of illicit drugs other than

marijuana.

! Initiation of marijuana use before age 15 was associated with a greater risk

of illicit drug dependence or abuse at age 26 or older. Relative to adults

who had initiated marijuana use at age 21 or older, adults who had first

used before age 15 were 6 times as likely to be dependent on an illicit

drug.
3

1. Introduction

1.1 Purpose of the Report

Estimates of first-time drug use, referred to as incidence or initiation, provide an

important measure of the Nation's drug use problem. They suggest emerging patterns of use and

identify periods of heightened risk for an immediate focus on the prevention of substance use,

particularly among children and youths. Incidence data also suggest the future burden on

substance abuse treatment systems.

This report contains an analysis of the initiation of marijuana use. Marijuana is the most

widely used illicit drug in the United States and is in most cases the first illicit drug used by

persons who have used an illicit drug. The analysis is based on data from the 1999 and 2000

National Household Surveys on Drug Abuse (NHSDAs). Overall estimates of the prevalence and

rate of marijuana initiation based on combined 1999 and 2000 data were released in September

2001 (Office of Applied Studies [OAS], 2001b). Those results showed that, although there was a

decrease in incidence from 2.6 million new users in 1996 to 2.0 million in 1999, these levels

were still significantly higher than the levels in 1990 (1.4 million). The purpose of this report is

to present more in-depth analyses of incidence rates among population subgroups, demographic

characteristics and predictors of recent initiates, and consequences of early marijuana initiation.

Specifically, this report has four objectives:

! estimate incidence rates and trends of marijuana use,

! provide State-specific incidence estimates,

! identify characteristics and predictors of recent marijuana initiates, and

! examine the relationship between early marijuana use and later drug use

patterns.

The report is organized into seven chapters and two appendices. Chapter 2 describes the

data source, measures of key study variables, and statistical methods. Chapter 3 presents

incidence rates and trends of marijuana use based on the combined 1999 and 2000

computer-assisted interviewing (CAI) data. Chapter 4 summarizes incidence rates by State using

small area estimation (SAE) methods. Chapter 5 examines social and demographic

characteristics of recent marijuana initiates and predictors of initiation. This chapter also

examines the relationship of marijuana initiation with school status, employment, and marital

status among those aged 18 to 25 years. Chapter 6 addresses the relationship between early

marijuana use and later drug use patterns, including lifetime and past year use of heroin, cocaine,
4

and psychotherapeutics nonmedically; heavy marijuana use; heavy illicit drug use other than

marijuana; abuse of and/or dependence on alcohol or other drugs; marijuana dependence; illicit

drug dependence other than marijuana; illicit drug dependence; and alcohol dependence. Chapter

6 also reports findings on the relationship between the age at onset of marijuana use and past

year drug dependence among lifetime marijuana users aged 26 or older who also used marijuana

in the past year. Chapter 7 provides a summary of overall findings and conclusions and discusses

some implications. Appendix A discusses the statistical methods used and the limitations of the

NHSDA data, describes the statistical methods for calculating incidence rates and potential

biases associated with incidence estimates, and discusses the change in NHSDA measures of

substance use initiation and its impact on incidence rate calculation. Appendix B presents

selected standard error tables for population estimates in the report. Appendix C provides

selected questionnaire pages from the 1999 and 2000 NHSDAs on the demographic and

marijuana questions.

1.2 Background on Marijuana Use and Initiation of Marijuana Use

1.2.1 Recent Trends in Use

Marijuana is the most widely used illicit drug in the United States (OAS, 2001b).

According to the 2000 NHSDA, an estimated 14.0 million Americans were current (past month)

marijuana users (OAS, 2001b). This represents 6.3 percent of people aged 12 or older and 76

percent of current illicit drug users. Of all current illicit drug users, approximately 59 percent

used only marijuana, 17 percent used marijuana and another illicit drug, and the remaining 24

percent used only an illicit drug other than marijuana in the past month (OAS, 2001b).

The NHSDA and the Monitoring the Future (MTF) have shown generally similar longterm trends in the prevalence of substance use among youths, regardless of substantial

differences in methodology between the two primary surveys of youth substance use. Between

1999 and 2000, both the NHSDA and MTF found no significant changes in lifetime, past year,

and current use of marijuana (Johnston, O'Malley, & Bachman, 2001; OAS, 2001b).

The MTF found that marijuana use rose particularly sharply among 8th graders in the

1990s, with annual prevalence tripling between 1991 and 1996 (i.e., from 6 to 18 percent)

(Johnston et al., 2001). Starting a year later, marijuana use also rose significantly among 10th and

12th graders. Following the recent peak in 1996-1997, annual marijuana use declined somewhat

in recent years (Johnston et al., 2001).
5

1.2.2 Prior Studies of Marijuana Initiation

Although the prevalence of marijuana use has been studied widely, relatively few

incidence (first use) data are available. In the first published analysis of national incidence

trends, Gfroerer and Brodsky (1992) estimated the number of new users of marijuana and other

drugs based on combined data of 1985 to 1991 NHSDAs. They found that fewer than half a

million people per year began using marijuana before 1966 and that new use of marijuana began

increasing after 1966, reaching a peak in 1973 and declining thereafter. Johnson, Gerstein,

Ghadialy, Choi, and Gfroerer (1996) studied the incidence of alcohol, cigarettes, and illicit drugs

using data from the 1991 to 1993 NHSDAs. Their investigation found declining trends of

marijuana initiation at all ages since at least the late 1970s. However, the mean age of marijuana

initiates declined throughout most of the measurement period, from older than 19 years in the

mid-1960s to younger than 18 years in the late 1980s and early 1990s. In addition, the rates of

marijuana initiation at ages 12 to 17 (youths) and 18 to 25 (young adults) in the early 1990s were

still much higher than corresponding rates in the early 1960s.

In recent years, youths aged 12 to 17 have constituted about two thirds of the new

marijuana users, with young adults aged 18 to 25 constituting most of the remaining third (OAS,

2001b). Additionally, recent rates of new use among youths in 1996-1998 (averaging 86.4

initiates per 1,000 potential new users) were higher than they had ever been. Nonetheless, rates

of new use for both youths and young adults decreased between 1998 and 1999. The average age

of marijuana initiation has generally declined since 1965 and remained around 17 years after

1992 (OAS, 2001b). 

1.2.3 Research on Seasonality of Substance Use

There are no known prior studies of seasonal patterns in the initiation of substance use. A

few studies, however, have looked at seasonal patterns in use. Zingraff and Belyea (1983)

suggested a possibility of increased rates of marijuana use during the summer months; other

researchers have suggested that variations in activities during the different seasons may

influence substance use (McKee, Sanderson, Chenet, Vassin, & Skolnikov, 1998). Kovalenko et

al. (2000) studied the seasonality in symptoms of mental and substance use disorders among

youths aged 9 to 17 and found a weak seasonality in the counts of symptoms of marijuana use,

with estimated zeniths in August and September. The investigators suggested that the possible

seasonality in marijuana use may be related to the cycles in school attendance.

On the other hand, one analysis found a lower prevalence of current marijuana during

July to September. Using data from 1992-1996 NHSDAs, Huang, Schildhaus, and Wright (1999)

examined the seasonality of past month substance use on a quarterly basis. In their logistic

regression model controlling for survey year, age, gender, race/ethnicity, and region, current use
6

of the following substances among youths aged 12 to 17 was observed to show seasonal

differences: alcohol, an illicit drug except marijuana, marijuana only, an illicit drug, and heavy

drinking. Youths were 1.3 times more likely to engage in current marijuana use only in Quarter 4

(October-December) than in Quarter 3 (July-September). Relative to Quarter 3, youths also were

1.2 times more likely to use an illicit drug in Quarter 1 (January-March). Further analyses found

that, during Quarter 3, youths were significantly less likely to report being approached by drug

dealers in the past month than in the other quarters. 

1.2.4 Predictors of Initiation

Little research exists on the predictors of marijuana initiation. Van Etten and Anthony

(1999) examined the initial opportunity to try marijuana and the transition from first opportunity

to first marijuana use using data from the 1979 to 1994 NHSDAs. They found that an estimated

51 percent of U.S. residents had an opportunity to try marijuana. One striking finding is that 43

percent of those with an opportunity went on to first use marijuana within 1 year of the first

opportunity (i.e., making a rapid transition). The study also found that males were more likely

than females to have an opportunity to use marijuana, but were not more likely to eventually use

marijuana once an opportunity was presented. Research has also shown that the risk of initiating

marijuana use is associated with age and birth cohort. Chen and Kandel (1995) found that the

major risk period for initiation into marijuana was mostly over by age 20. Gfroerer and Epstein

(1999) also found that marijuana initiation was unlikely to occur after age 21. Rates of first

marijuana use were higher among younger people and cohorts born after World War II than

older people and cohorts born before World War II (Johnson et al., 1996; Johnson & Gerstein,

1998).

The onset of marijuana use also is influenced by a variety of personal, family, and

community risk and protective factors, such as affiliation with drug-using peers, personality

dimensions (e.g., unconventionality), and the parent-child bond (Brook et al., 1999a; Clayton,

1992).

1.2.5 Sequencing of Substance Use Initiation

Marijuana has been hypothesized to be a gateway drug for other illicit drug use. Studies

by Kandel and other investigators have identified a developmental sequence of drug involvement

among youths (Ellickson, Hays, & Bell, 1992; Kandel, Yamaguchi, & Chen, 1992; Yamaguchi

& Kandel, 1984). Specifically, the initial use of alcohol and/or cigarettes typically precedes the

use of marijuana, which then is followed by the involvement of other illicit drugs. By studying a

sample of rural youths, Donnermeyer (1993) also found that early use of alcohol predicted early

use of marijuana, which in turn was predictive of early use of other illicit drugs. Studies of age at

initiation of drug use confirmed that initiation of alcohol or tobacco typically occurred before
7

marijuana initiation (Costello, Erkanli, Federman, & Angold, 1999; Kosterman, Hawkins, Guo,

Catalano, & Abbott, 2000).

1.2.6 Early Marijuana Use and Later Substance Use Problems

Not only does early marijuana use signal an increased risk for hard drug use by grade 10

(Ellickson & Morton, 1999), but it also is associated with drug use problems, dependency, and

treatment need (Brook, Richter, Whiteman, & Cohen, 1999b; Clark, Kirisci, & Tarter, 1998;

Gfroerer & Epstein, 1999). Among individuals with a history of marijuana dependence, the age

at onset of marijuana dependence was younger in the adolescent-onset individuals compared

with the adult-onset individuals, and the time from the first use to the onset of dependence also

was shorter in the adolescent-onset individuals (Clark et al., 1998). Among middle school

students, use of marijuana and other drugs before the age of 12 was found to be associated with

engaging in greater numbers of health risk behaviors than among students whose age at onset

was 12 years or older or the never users (DuRant, Smith, Kreiter, & Krowchuk, 1999). Early

marijuana use is associated with later adolescent problems that limit the acquisition of skills

necessary for employment and increased risk of contracting the human immunodeficiency virus

(HIV) and using illicit drugs (Brook et al., 1999b). Gfroerer and Epstein (1999) used NHSDA

data to examine the impact of marijuana initiation on future drug abuse treatment need and found

age at first use of marijuana as the most significant predictor of treatment need in all four age

groups (i.e., 12 to 17, 18 to 25, 26 to 34, and 35 or older).

The number of new marijuana users may have a significant impact on the future demand

for substance abuse treatment as some new users continue into heavier marijuana use or other

illicit drug taking. Consequently, delaying the onset of marijuana initiation could be important in

preventing the progression into heavy drug involvement and other drug-related health risk

behaviors, as well as in decreasing the social burdens of illicit drug use.

Taken together, studies of marijuana initiation provide vital information for focused

prevention programs about the periods of heightened initiation risk, specify subgroups

vulnerable to initial use, and generate estimates on treatment needs and future demand for

substance abuse treatment.
8
9

2. Data and Methods

2.1 Data Source

The National Household Survey on Drug Abuse (NHSDA) is the primary source of

statistical information on the use of licit and illicit drugs by the U.S. population aged 12 or older.

Conducted by the Federal Government since 1971, the survey collects data by administering

questionnaires to a representative sample of the population through face-to-face interviews at

their place of residence. The survey is sponsored by the Substance Abuse and Mental Health

Services Administration (SAMHSA). Data collection is carried out by RTI of Research Triangle

Park, North Carolina, under a contract with SAMHSA's Office of Applied Studies (OAS).

The target population covers residents of households, noninstitutional group quarters

(e.g., shelters, rooming houses, dormitories), and civilians living on military bases. Persons

excluded from the survey include homeless people who do not use shelters, active military

personnel, and residents of institutional group quarters, such as prisons and long-term hospitals.

The survey is conducted from January through December each year.

Prior to 1999, the NHSDA was administered in about an hour and used paper-and-pencil

interviewing (PAPI) methods. The NHSDA PAPI instrumentation consisted of a questionnaire

booklet completed by the interviewer and a set of individual answer sheets completed by the

respondent. All substance use questions and other sensitive questions appeared on the answer

sheets so that the interviewer was not aware of the respondent's answers. Less sensitive

questions, such as demographics, occupational status, and household size and composition, were

asked aloud by the interviewer and recorded in the questionnaire booklet.

Beginning in 1999, the NHSDA underwent a major redesign. The new features of the

survey design produce a significant impact on the NHSDA estimates for substance use. In

addition to the following summary, see the report titled Development of Computer-Assisted

Interviewing Procedures for the 1999 National Household Survey on Drug Abuse (OAS, 2001a).

First, the method of data collection was changed from a paper questionnaire

administration to a computer-assisted administration. The 1999 NHSDA marked the first survey

year in which the national sample was interviewed using a computer-assisted interviewing (CAI)

methodology. The survey used a combination of computer-assisted personal interviewing

(CAPI) conducted by the interviewer and audio computer-assisted self-interviewing (ACASI).

For the most part, questions previously administered by the interviewer are now administered by

the interviewer using CAPI, and questions previously administered using answer sheets are now
10

administered using ACASI. The CAI method has many advantages over PAPI, including more

efficient collection and processing of the data and improved data quality.

Use of ACASI is designed to provide the respondent with a highly private and

confidential means of responding to questions and should increase the level of honest reporting

of illicit drug use and other sensitive behaviors. The interview averages about an hour. In brief,

the interview begins in CAPI mode with the field interviewer (FI) reading the questions from the

computer screen and entering the respondent's replies into the computer. The interview then

transitions to the ACASI mode for the sensitive questions. In this mode, the respondent can read

the questions silently on the computer screen and/or listen to the questions read through

headphones and enter his or her responses directly into the computer. At the conclusion of the

ACASI section, the interview returns to the CAPI mode with the interviewer completing the

questionnaire. No personal identifying information is captured in the CAI record for the

respondent.

Second, the sample design was changed from a strictly national design to a State-based

sampling plan. Beginning in 1999, the NHSDA sample employed a 50-State design with an

independent, multistage area probability sample for each of the 50 States and the District of

Columbia. The eight States with the largest population (which together account for 48 percent of

the total U.S. population aged 12 or older) were designated as large sample States (i.e.,

California, Florida, Illinois, Michigan, New York, Ohio, Pennsylvania, and Texas). For these

States, the design provided a sample large enough to support direct State estimates. For the

remaining 42 States and the District of Columbia, smaller, but adequate samples were selected to

support State estimates using small area estimation (SAE) techniques. The design also

oversampled youths and young adults so that each State's sample was approximately equally

distributed among three major age groups: 12 to 17 years, 18 to 25 years, and 26 years or older.

The NHSDA also tripled its sample size in 1999, which makes it possible to produce

marijuana use estimates separately for every State and the District of Columbia and for smaller

population subgroups. It also allows more detailed analyses of national patterns of use,

predictors of recent initiation, and consequences of early first use of marijuana. The precision of

the estimates at the national level has been improved substantially. The CAI methodology has

made data collection and processing more efficient and improved the quality of the data.

However, because of the major differences between the CAI and PAPI methods, it is not

appropriate to compare the 1999 and 2000 CAI estimates of substance use with earlier NHSDA

estimates in order to assess changes over time in substance use. In addition, the sample

expansion had unexpected effects on some aspects of the data collection. In-depth analyses of

these methodological issues are described in another SAMHSA report (Gfroerer, Eyerman, &

Chromy, in press).
11

Third, beginning in 1999, the NHSDA questionnaire allows for collecting year and 

month of first use for recent initiates (i.e., new drug users). In addition, the questionnaire call

record provides the date of the interview. Exposure time to substances can be determined in

terms of days and converted to an annual measure. Having data about exact dates of birth and

first use allows person time of exposure to a drug during the targeted period to be determined. In

prior years, before exact date data were available for computing incidence of drug use, the

calculation of the person time exposure for incidence rates of drug use was based on an

approximation, rather than an exact computation for each person. Thus, because of the changes

in methodology since the 1999 NHSDA, the estimates from the 1999 and 2000 surveys are not

completely comparable with data obtained from prior surveys. Nonetheless, because all

incidence estimates in this report, including pre-1999 estimates, are based on the 1999 and 2000

NHSDAs, they are comparable. A more complete discussion of the differences between the old

and new incidence estimates is presented elsewhere (Chromy, in press; Gfroerer et al., in press).

2.2 Limitations of the Data

Regardless of the survey year, the NHSDAs are all based on retrospective reports by

survey respondents, and they may be subject to similar kinds of recall and reporting biases.

Some sources of biases are related to the NHSDA designs and retrospective self-reports.

First, some degree of underreporting on drug use-related behaviors might have occurred

because of the social acceptability of drug use behaviors and respondents' fear of disclosure.

Prior studies showed that underreporting of drug use among youths in their homes may be

substantial (Gfroerer, 1993; Gfroerer, Wright, & Kopstein, 1997). Self-report data also are

influenced by memory and recall errors, including recall decay (tendency to forget events

occurring long ago) and forward telescoping (tendency to report that an event occurred more

recently than it actually did). These memory errors would both tend to result in estimates for

earlier years (i.e., 1960s and 1970s) that are downwardly biased (because of recall decay) and

estimates for later years that are upwardly biased (because of telescoping).

Second, the NHSDA target population focuses on civilian, noninstitutionalized household

residents. Although it includes almost 98 percent of the U.S. population aged 12 or older, some

population subgroups who may have different drug-using patterns are excluded, such as active

military personnel, people living in institutional group quarters, and homeless persons not living

in identifiable shelters. Thus, the generalizability of the findings to the excluded subgroups is

limited. Further, the estimates for drug use should be considered conservative.

Third, there is a potential bias associated with differential mortality because some

individuals who were exposed to the risk of first drug use in the historical periods shown in the
12

tables died before the 1999 NHSDA was conducted. This bias is probably very small for

analyses of recent marijuana initiation.

Fourth, marijuana incidence trends based on NHSDA data may be biased. Johnson,

Gerstein, and Rasinski (1998) concluded that the marijuana incidence trend from the NHSDA

may be biased because the reporting of initiation declines as the length of time between initiation

and the survey increases. However, their analysis did not address very recent estimates, which

could be biased because they reflect recent drug use and because they are heavily based on the

reports of adolescents. Appendix A presents estimates for cocaine, heroin, and marijuana use

based on single years of NHSDA data in order to better understand the size of the biases and to

assess the reliability of estimates for recent years. This analysis shows that marijuana initiation

rates appear to have small biases.

2.3 Analysis Sample 

A total of 66,706 respondents aged 12 or older completed the 1999 survey, and a total of

71,764 respondents completed the 2000 survey (Tables 2.1 and 2.2). The analysis samples for

this report vary depending on the specific objective of the chapter. The full sample of 1999 and

2000 CAI data (N = 138,470) was used to estimate trends in the incidence of marijuana use

(Chapter 3), as well as State-level incidence rates (Chapter 4). The characteristics of recent

initiates (Section 5.2) were examined in a sample consisting of individuals who started to initiate

marijuana use in 1998 and individuals who had never used marijuana prior to 1998 in the 1999

NHSDA, as well as 1998 and 1999 marijuana initiates and individuals who had never used

marijuana prior to 1998 in the 2000 NHSDA (n = 99,752). The analysis of seasonality (Section

5.3) was based on all marijuana users who were asked the month of first use question and

reported it (i.e., no imputed data) (n = 2,085). These users reflect persons interviewed during

1999 and 2000 who initiated marijuana either at their current age or at 1 year less than their

current age. Although this captures some initiation occurring in 1997 and 2000, it primarily

represents 1998 and 1999 initiation.

The sample for the analysis of predictors of recent initiation (Section 5.4) was restricted

to 1998 marijuana initiates and individuals who had never used marijuana prior to 1998 in the

1999 NHSDA, as well as 1999 marijuana initiates and individuals who had never used marijuana

prior to 1999 in the 2000 NHSDA (n = 97,530). Using this sample allows the analysis to reflect

the population that had never used marijuana at a point in time and model the transition from

nonuse to use over a 1-year time period.

For the analysis of the relationship between early use and later drug use patterns (Chapter

6), the sample included all lifetime marijuana users aged 26 or older in 1999 and 2000 CAI data
13

(n = 16,652). Because the 1999 questionnaire did not fully represent the criteria in the 4th edition

of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric

Association [APA], 1994), the analysis of substance dependence and/or abuse was conducted on

data from the 2000 survey (n = 8,927). A subset of the analysis investigated whether the risk of

substance dependence and/or abuse was greater for early initiates than late initiates among

lifetime marijuana users who used it in the past year. The analysis sample was based on lifetime

marijuana users aged 26 or older who also used marijuana in the past year (n = 1,447).

2.4 Measures and Definitions of the Terms Used in the Report

This section describes the NHSDA measures and definitions of the following study

variables: first marijuana use; social and demographic variables; use of cigarettes, alcohol, and

other drugs; heavy use of illicit drugs; and dependence on or abuse of alcohol and other drugs.

2.4.1 First Marijuana Use

Estimates of first use, incidence, or initiation of marijuana use were based on the

following questions: age at first use, year and month of first use for recent initiates, the

respondent's date of birth, and the interview date. By using this information, along with editing

and imputation when necessary, an exact date of first use was determined for each marijuana

user. Recent marijuana initiates were defined as persons who reported that their first use of

marijuana occurred during 1998 or 1999. Age at first marijuana use was defined as self-reported

age at first use of marijuana and was grouped into four categories (i.e., aged 14 or younger, 15 to

17, 18 to 20, and 21 or older).

2.4.2 Social and Demographic Variables

A range of social and demographic variables was included in the 1999 and 2000

NHSDAs. Age of the respondent was defined as "age at time of interview." In the predictor

analysis (Section 5.4), age was defined as "age on January 1, 1998" in the 1999 survey and as

"age on January 1, 1999" in the 2000 survey. Race/ethnicity was coded into the following

categories: (a) non-Hispanic whites (referred to as "whites"); (b) non-Hispanic blacks (referred

to as "blacks"); (c) Hispanics; (d) non-Hispanic American Indians/Alaska Natives; (e) nonHispanic Asians/Pacific Islanders/Native Hawaiians; and (f) non-Hispanic persons reporting

more than one race. Level of education (for 18 to 25 year olds only) was categorized into four

groups: school dropouts, high school students, high school graduates, and college students or

graduates. A school dropout was defined as an individual aged 18 to 25 who had completed less

than the 12th grade, reported not being currently enrolled in school, and did not have a high

school degree or take an equivalency exam (e.g., a general equivalency diploma [GED]).
14

Employment status (for 18 to 25 year olds only) was categorized into employed persons (fulltime or part-time) and not employed persons (unemployed individuals, students, or others). Not

employed persons in this age group primarily consist of students. Marital status was categorized

into two groups: never married and ever married (for 18 to 25 year olds only).

Population density was grouped into three categories: large metropolitan, small

metropolitan, and nonmetropolitan. Large metropolitan areas had a population of 1 million or

more; small metropolitan areas had a population of less than 1 million; and nonmetropolitan

areas were areas outside metropolitan statistical areas (MSAs). Residential region was

categorized into four regions: Northeast, Midwest, South, and West. The Northeast region has

nine States: Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York,

Pennsylvania, Rhode Island, and Vermont. The Midwest region has 12 States: Illinois, Indiana,

Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota,

and Wisconsin. The South region has 16 States, as well as the District of Columbia: Alabama,

Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North

Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia. And the

West region has 13 States: Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana,

Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.

2.4.3 Use of Cigarettes, Alcohol, and Other Drugs

The definitions for the use of cigarettes, alcohol, and other drugs include past year use

and lifetime use. Lifetime use referred to a respondent reporting any use of the substance at least

once in his or her lifetime. Past year use referred to a respondent reporting any use of the

substance at least once during the 12 months preceding the interview date. Use of

psychotherapeutic drugs was defined as any nonmedical use of prescription-type pain relievers,

sedatives, tranquilizers, or stimulants (i.e., when it was not prescribed for the respondent, or used

only for the experience or feeling it caused). Pain relievers include painkillers like Darvon,

Demerol, Percodan, and Tylenol with codeine. Sedatives are sometimes referred to as "downers"

and include barbiturates, sleeping pills, and Seconal. Tranquilizers include antianxiety drugs,

such as Librium, Valium, Ativan, and Meprobamate. Stimulants are often called "uppers" or

"speed" and include amphetamines and Preludin.

2.4.4 Heavy Use of Illicit Drugs

Heavy marijuana use was defined as using marijuana daily or almost daily in the past

year (i.e., at least 300 days). Heavy use of other illicit drugs referred to using one or more of the

following drugs on at least 50 days in the past year: cocaine, hallucinogens, heroin, inhalants,

pain relievers, sedatives, tranquilizers, or stimulants, regardless of heavy marijuana use.
15

2.4.5 Dependence on or Abuse of Alcohol and Other Drugs

The 2000 NHSDA included a series of questions to assess substance dependence and

abuse based on DSM-IV criteria (APA, 1994). The seven dependence criteria are (1) tolerance;

(2) withdrawal or avoidance of withdrawal; (3) persistent desire or unsuccessful attempts to cut

down or stop substance use; (4) spending a lot of time using the substance, obtaining the

substance, or recovering from its effects; (5) reducing or giving up occupational, social, or

recreational activities in favor of substance use; (6) impaired control over substance use; and (7)

continuing to use the substance despite physical or psychological problems. A respondent was

considered to be dependent on a substance when he or she reported having at least three of the

dependence criteria.

The four substance abuse criteria are (1) having serious problems due to substance use at

home, work, or school; (2) the use of that substance putting the respondent in physical danger;

(3) substance use causing the respondent to be in trouble with the law; and (4) continuing to use

the substance despite having substance-use-related problems with family and friends. A

respondent was classified with abuse when he or she reported having at least one of the four

abuse criteria.

The following types of substance dependence or abuse were studied in relation to age at

first use of marijuana:

! Illicit Drug Dependence or Abuse: dependence on or abuse of an illicit

drug in the past year (i.e., marijuana, cocaine/crack, hallucinogens,

inhalants, heroin, pain relievers, sedatives, tranquilizers, or stimulants).

! Alcohol or Illicit Drug Dependence or Abuse: dependence on or abuse of

either alcohol or an illicit drug in the past year (i.e., marijuana,

cocaine/crack, hallucinogens, inhalants, heroin, pain relievers, sedatives,

tranquilizers, or stimulants).

! Illicit Drug Dependence: dependence on an illicit drug in the past year

(i.e., marijuana, cocaine/crack, hallucinogens, inhalants, heroin, pain

relievers, sedatives, tranquilizers, or stimulants).

! Alcohol Dependence: dependence on alcohol in the past year.

! Marijuana Dependence: dependence on marijuana in the past year.

! Other Illicit Drug Dependence: dependence on cocaine/crack,

hallucinogens, inhalants, heroin, pain relievers, sedatives, tranquilizers, or

stimulants in the past year, regardless of marijuana dependence. 
16

2.5 Statistical Methods

2.5.1 Incidence Estimation: National

SUrvey DAta ANalysis (SUDAAN) software (Shah, Barnwell, & Bieler, 1996) was used

for the analyses to take into account the complex survey design of the NHSDA. The incidence

rate of marijuana was defined as the rate of new marijuana users in a given year (i.e., the number

of new marijuana users divided by the person time of exposure) (Appendix A). By applying

sample weights to the incidence of first use, estimates of the number of new users for each year

were made. The incidence of first use was classified by year of occurrence. For age-specific

incidence rates, the period of exposure was defined for each respondent and age group for the

time that the respondent was in the age group during the calendar year. For the analysis that used

aggregated 1999 and 2000 data, sample weights were adjusted to obtain a simple average weight

over 2 years (i.e., averaging the weights by dividing them by two).

2.5.2 Incidence Estimation: State

The average annual numbers of marijuana initiates and rates by State, as reported in

Chapter 4, were obtained using small area estimation (SAE) methods applied to the pooled

1999-2000 survey data and are, therefore, different from incidence estimates reported in the

other chapters. A detailed discussion of the SAE methodology can be found in State Estimates of

Substance Use from the 2000 NHSDA (Wright, in press).

In brief, NHSDA State estimates of each substance use measure are produced by

combining an estimate of the measure based on the State sample data with the estimate of the

measure based on a national regression model applied to local-area county and Census block

group/tract-level estimates from the State. The parameters of the regression model are estimated

from the entire national sample. Because the 42 smaller (in terms of population) States and the

District of Columbia have smaller samples than the eight large States, estimates for the smaller

States rely more heavily on the national model. The model for each substance use measure

typically utilizes from 50 to 100 independent variables in the estimation. These variables include

basic demographic characteristics of respondents (e.g., age, race/ethnicity, and gender),

demographic and socioeconomic characteristics of the Census tract or block group (e.g., average

family income and percentage of single-mother households), and county-level substance abuse

and other indicators (e.g., rate of substance abuse treatment, drug arrest rate, and drug- and

alcohol-related mortality rate). Population counts by State and age group are applied to the

estimated rates to obtain the estimated number of persons with the substance use characteristic. 
17

Corresponding to each SAE estimate is a 95 percent prediction interval (PI) that indicates

the precision of the estimate. The PI accounts for variation due to sampling as well as variation

due to the model and is derived from the process that generates the State SAE. There is a 95

percent probability that the true value lies within the interval.

The incidence estimates discussed in this report are based on the combination of two

separate measures: (1) the number of marijuana initiates during the past 24 months, and (2) the

number of persons who have never used marijuana. Each of these measures is generated

independently using SAE, by State and age group. The following formula was used to generate

the average annual rate of first use of marijuana for each State:

Average annual incidence rate = 

0.5 * {Number of initiates in past 24 months / 

[(Number of initiates in past 24 months * 0.5) + Number of persons who never used]}.

2.5.3 Logistic Regression Analyses

Logistic regression procedures were used to (1) determine the characteristics and

suspected predictors of recent initiation and (2) examine the relationship between early onset of

marijuana use and later drug use patterns (e.g., heavy illicit drug use, alcohol and/or illicit drug

dependence or abuse). Odds ratio (OR) estimates derived from logistic regression procedures

denote the estimated magnitude of an association between a binary outcome and a covariate. In

this report, the p value equal to or less than .05 is considered statistically significant. The OR

estimate greater than 1 indicates a positive association between the outcome of interest and the

covariate; a value of less than 1 reflects an inverse association.
18

Table 2.1 Survey Sample Sizes for All Respondents Aged 12 or Older, by Age Group and Demographic CharacterDemographic Characteristic

Total

Age Group (Years)

12-17 18-25 

1999 2000 1999 2000 1999 2000 

Total 66,706 71,764 25,357 25,717 21,933 22,613 1Gender

Male 32,092 34,386 12,798 12,977 10,411 10,716 

Female 34,614 37,378 12,559 12,740 11,522 11,897 1

Hispanic Origin and Race

Not Hispanic

White only 46,054 49,415 16,90 17,047 14,697 14,991 1Black only 7,982 8,494 3,297 3,367 2,729 2,711 

American Indian or Alaska

Native only 739 769 273 288 278 270 

Native Hawaiian or other

Pacific Islander 232 261 92 92 84 108 

Asian only 2,146 2,393 795 784 765 856 More than one race 1,072 1,039 483 468 380 352 

Hispanic 8,481 9,393 3,516 3,671 3,000 3,325 

Adult Education1

< High school 7,458 8,376 N/A N/A 4,347 4,771 High school graduate 14,845 16,026 N/A N/A 8,218 8,234 Some college 11,692 12,577 N/A N/A 6,990 6,954 College graduate 7,354 9,068 N/A N/A 2,378 2,654 

Current Employment1

Full-time 23,723 26,826 N/A N/A 11,433 11,984 1Part-time 7,220 7,567 N/A N/A 5,184 5,113 Unemployed 1,705 1,706 N/A N/A 1,266 1,237 Other2 8,701 9,948 N/A N/A 4,050 4,279 

N/A: Not applicable.1 Data on adult education and current employment not shown for youths aged 12 to 17. Estimates for both adult education and current employment are for persons aged 2 Retired, disabled, homemaker, student, or “other.”

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
19

Table 2.2 Survey Sample Sizes for All Respondents Aged 12 or Older, by Age Group and Geographic C

and 2000

Geographic Characteristic

Total

Age Group (Years)

12-17 18-25 

1999 2000 1999 2000 1999 2000 

Total 66,706 71,764 25,357 25,717 21,933 22,613 Geographic Division

Northeast 11,830 14,394 4,475 5,102 3,656 4,310 Midwest 18,103 19,355 6,530 6,655 6,165 6,236 South 21,018 22,041 7,731 7,856 7,189 7,189 West 15,755 15,974 6,621 6,104 4,923 4,878 

County Type

Large metro 25,901 28,744 10,116 10,576 8,121 8,759 Small metro 22,612 24,579 8,316 8,505 7,859 8,108 Nonmetro 18,193 18,441 6,925 6,636 5,953 5,746 

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
20
21

3. Trends in Marijuana Incidence

3.1 Introduction

Estimates of marijuana incidence, or the number of new marijuana users during a given

year, provide an important measure of the Nation's marijuana use problem. They can suggest

emerging patterns of use, give clues about the changes in the prevalence of use, identify at-risk

subgroups for targeting prevention programs, and suggest substance abuse treatment needs for

the Nation.

 This chapter presents incidence estimates of marijuana use based on data from the 1999

and 2000 National Household Surveys on Drug Abuse (NHSDAs). These incidence estimates are

based on the NHSDA questions on age at first use, year and month of first use for recent

initiates, the respondent's date of birth, and the interview date. Using this information, along with

editing and imputation when necessary, an exact year, month, and day of first use was

determined for each substance used by each respondent. Because these data were collected on a

retrospective basis, incidence estimates were always 1 year behind the data on current use. For

age-specific incidence rates, the period of exposure was defined for each respondent and age

group for the time that a respondent was in an age group during a calendar year.

The average age of new users in each year also was estimated. These rates are presented

in this report as the number of new marijuana users per 1,000 potential new users because they

indicate the rate of new use among persons who had not yet used the drug (i.e., potential new

users). More precisely, the rates are actually the number of new users per 1,000 person-years of

exposure. The numerator of each rate is the number of persons in the age group who first used

the drug in the year. The denominator is the person time exposure measured in thousands of

years. Each person's exposure time ends on the date of first use. For age-specific estimates,

exposure is limited to the time during the year that the person was in that age group. Persons

who first used the drug in a prior year had zero exposure to first use in the current year, and

persons who still had never used the drug by the end of the current year had 1 full year of

exposure to the risk.

Because these incidence estimates were based on retrospective reports, they were subject

to several biases, as discussed in Chapter 2. It is possible that some of these biases, particularly

telescoping and underreporting because of fear of disclosure, may affect estimates for the most

recent years more significantly. However, further analysis is needed to understand the magnitude

of these biases. In addition, the estimates in this report were based on the new CAI data, and the

estimation methodology for these estimates was different from that used in NHSDAs prior to

1999 (i.e., based on paper-and-pencil interviewing [PAPI] methodology). The revised
22

methodology had an impact on age-specific rates (Gfroerer et al., in press). Thus, comparisons

with prior NHSDA estimates should not be made.

Estimated trends and incidence rates of marijuana use reported in this chapter were based

on the combined sample of 1999 and 2000 CAI data. These estimates are presented by the

overall sample, combined age groups and gender (e.g., 12 to 14 male, 12 to 14 female, 15 to 17

male, 15 to 17 female, 18 to 20 male, 18 to 20 female, 21 or older male, and 21 or older female),

and race/ethnicity (e.g., white, black, Hispanic, Asian/Pacific Islander/Native Hawaiian,

American Indian/Alaska Native, and persons reporting more than one race).

3.2 Trends in Marijuana Incidence

Table 3.1 summarizes the estimated number of new marijuana users, mean age of first

use, and annual incidence rates from 1999 and 2000 NHSDA data. An estimated 2.0 million

Americans aged 12 or older used marijuana for the first time in 1999, which was fewer than the

estimated number of new users in 1998 (approximately 2.5 million Americans), but still above

the 1989 and 1990 levels (1.4 million each year). Figure 3.1 shows that the rate of marijuana

initiation increased during the late 1960s and early 1970s, with a peak in 1976 and 1977 (21.0

per 1,000 potential new users). After that period, the rate of new marijuana use decreased to 8.5

in 1990, followed by an increase to 16.8 in 1996, then a decrease to 13.6 in 1999. The mean age

at first use was 19 years in the early 1970s and decreased to 17 years in the 1990s.

3.3 Trends, by Age and Gender

Over the years, rates of marijuana incidence were generally higher among males than

among females (Tables 3.2 and 3.3, Figure 3.2). Among males, the rate increased dramatically

from 4.9 in 1965 to 22.9 in 1971. The highest peak was noted in 1976-1977 (close to 24). After

the late 1970s, incidence rates for males declined to around 10 in the late 1980s, followed by a

period of increase during the 1990s to 19.3 in 1997. For females, the incidence rate increased

steadily from 3.3 in 1965 to 18.9 in 1976. Similar to the pattern of males, the rate was lower

during the 1980s, followed by an increase during the early 1990s. The most recent peak for

females was in 1996 (15.5). For both genders, the rate in 1999 (15.5 and 12.1, respectively, for

males and females) was lower than the rate in 1996-1998.

The estimated mean age at first marijuana use generally has been slightly younger in

males than in females. For males, the mean age at first marijuana use ranged from 18-19 years

during late 1960s to 16-17 years in recent years. For females, the mean age at first marijuana use

decreased from 20 years during late 1960s to around 17 years in recent years. The average age of

new marijuana users in 1999 was 16.4 years for males and 17.6 years for females.
23

Figure 3.1 Marijuana Incidence Rates, by YearNote: The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the person-tim

thousands of years for persons aged 12 or older.

* Estimated using 2000 data only.Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
24

Figure 3.2 Marijuana Incidence Rates, by Gender and YearNote: The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the person-tim

thousands of years for persons aged 12 or older.

* Estimated using 2000 data only.Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
25

Detailed data on age- and gender-specific incidence rates are summarized in Table 3.4.

The data indicate that trends of incidence rates peaked at different periods for youths and adults.

Among youths aged 12 to 17, annual incidence rates reached peaks during the late 1970s and late

1990s, and the pattern was similar for both genders. Among adults, particularly males, a peak

rate of initiation was reached during the late 1960s, with rates remaining high throughout the

1970s, before dropping significantly in the 1980s. In addition, among adults aged 21 or older, the

data did not show a peak in new use during the late 1990s, while persons aged 18 to 20 did.

3.4 Trends, by Race/Ethnicity

The trends of marijuana incidence also varied across racial/ethnic groups (Tables 3.5 to

3.7). In 1999, an estimated 1.4 million new marijuana users were white; there were 0.25 million

black initiates, 0.25 million Hispanic initiates, 0.04 million Asian initiates (including other

Pacific Islanders and Native Hawaiians), 0.03 million American Indian/Alaska Native initiates,

and 0.03 million initiates who reported more than one race. Except for American Indians/Alaska

Natives, the estimated numbers of new users were lower in 1999 than in 1998. In recent years,

American Indians/Alaska Natives appeared to have a younger mean age of first marijuana use

(14.1 years in 1999) than members of other racial/ethnic groups. In 1999, the mean age of

marijuana initiation was 17.2 years for whites, about 16.4 years for blacks and Hispanics, 18.8

for Asians (including other Pacific Islanders and Native Hawaiians), and 15.8 years for persons

reporting more than one race.

Among whites, the trend pattern was generally consistent with the overall trend seen in

Table 3.1. Probably because of small samples, more variation was noted for non-Hispanic

minority groups (American Indians/Alaska Natives, Asians/Pacific Islanders/Native Hawaiians, 

and persons reporting more than one race) and for years before 1990. Incidence rates between

1990 and 1999 for the racial/ethnic groupings are displayed in Figure 3.3.

Among blacks, the annual incidence rate (per 1,000 potential new users) increased from

8.0 in 1966 to 16.7 in 1968, reached a peak at about the same time as whites (19.4 in 1976), then

remained high throughout the late 1970s. Following the low rates in the 1980s, rates among

blacks rose again in the early 1990s, reached a peak in 1997 and 1998 (19.2 and 19.1,

respectively), then dropped to 14.0 in 1999. Similar to the general pattern for whites and blacks,

Hispanics' annual incidence rate rose during late 1970s and 1990s, with a peak in 1998 (17.8).

Asians (including other Pacific Islanders and Native Hawaiians) typically had lower

annual incidence rates than the other racial/ethnic groups. However, the sample size did not

allow for the generation of reliable estimates for trend data prior to 1985. Among recent initiates,

rates of first marijuana use by racial/ethnic groups were generally lower in 1999 than in 1998, 
26

Figure 3.3 Marijuana Incidence Rates, by Race/Ethnicity and YearNote: The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the person-tim

thousands of years for persons aged 12 or older.

* Estimated using 2000 data only.Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
27

with the exception of American Indians/Alaska Natives. Estimates from Table 3.7 suggest a

higher rate of new marijuana use in recent years among American Indians/Alaska Natives and

among persons reporting more than one race. The annual incidence rate among American

Indians/Alaska Natives was 21.2 (per 1,000) in 1995 and had risen over these years to a rate of

46.5 in 1999. Similar to the rates for American Indians/Alaska Natives, incidence rates among

persons reporting more than one race were higher than among other racial/ethnic groups during

the 1990s. Their incidence rate ranged from 26.2 to 35.4 between 1995 and 1999 compared with

a rate below 20.0 among whites, blacks, Hispanics, and Asians/Pacific Islanders/Native

Hawaiians.
28

Table 3.1 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana

During the Years 1965 to 1999, Their Mean Age at First Use, and the Annual

Incidence Rates of First Use (Per 1,000 Person-Years of Exposure), for All

Ages

Year Number of Initiates (1,000s) Mean Age at First Use Incidence Rates1

1965 553 20.4 4.0

1966 975 19.2 7.0

1967 1,385 19.5 9.7

1968 1,738 19.4 12.0

1969 2,123 19.0 14.5

1970 2,592 18.7 17.5

1971 2,789 18.7 18.7

1972 2,819 18.8 18.8

1973 2,854 18.6 19.0

1974 2,853 17.9 18.9

1975 2,874 18.3 19.0

1976 3,184 18.5 21.0

1977 3,163 18.3 20.9

1978 2,967 18.1 19.5

1979 2,859 18.1 18.7

1980 2,522 19.2 16.4

1981 1,867 17.9 12.0

1982 2,021 18.8 12.8

1983 1,865 18.2 11.7

1984 2,012 18.3 12.4

1985 1,865 18.1 11.4

1986 1,753 17.6 10.6

1987 1,588 17.6 9.5

1988 1,550 17.4 9.2

1989 1,447 17.7 8.7

1990 1,407 18.3 8.5

1991 1,485 18.0 9.1

1992 1,599 16.7 9.8

1993 1,954 17.2 12.2

1994 2,187 16.7 13.8

1995 2,357 16.5 15.1

1996 2,590 17.1 16.8

1997 2,494 17.0 16.5

1998 2,488 17.4 16.7

19992 2,028 17.0 13.6

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years for persons aged 12 or older. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
29

Table 3.2 Estimated Age-Gender Numbers (in Thousands) of Persons Who First Used

Marijuana During the Years 1965 to 1999

Year

Number of Initiates (1,000s)

Males

12-14

Females

12-14

Males

15-17

Females

15-17

Males

18-20

Females

18-20

Males

21+

Females

21+

1965 41 * 114 36 72 84 70 98

1966 64 * 159 86 271 129 142 102

1967 113 54 200 98 312 149 314 132

1968 98 38 248 109 552 195 293 184

1969 115 78 372 216 488 261 266 291

1970 197 187 435 328 496 279 333 303

1971 266 210 405 283 486 320 358 395

1972 264 148 496 453 414 308 385 326

1973 261 225 565 385 365 320 353 306

1974 245 271 584 468 329 301 253 307

1975 309 275 469 493 339 270 235 404

1976 213 208 665 603 414 317 303 420

1977 292 272 633 559 396 309 291 354

1978 263 221 691 542 317 341 230 296

1979 287 237 627 522 362 300 176 274

1980 184 165 486 531 215 297 249 312

1981 156 144 357 383 212 203 120 221

1982 189 132 385 391 254 215 154 258

1983 182 152 394 329 197 172 241 128

1984 237 176 382 385 209 207 160 215

1985 184 155 370 371 232 194 204 118

1986 155 134 361 382 212 183 159 118

1987 85 109 340 386 250 189 75 124

1988 132 80 348 327 210 164 112 136

1989 122 96 326 280 175 175 116 99

1990 130 94 309 240 197 135 103 148

1991 154 96 302 265 180 171 160 101

1992 185 159 347 258 222 173 104 82

1993 244 222 364 355 229 210 124 136

1994 276 261 450 394 242 234 123 121

1995 336 274 510 401 226 256 137 141

1996 350 294 523 523 235 268 138 202

1997 329 313 547 478 266 227 145 139

1998 334 313 519 467 236 250 154 175

19991 291 255 446 399 151 175 124 159

* Low precision; no estimate reported. 1 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
30

Table 3.3 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana During

the Years 1965 to 1999, Their Mean Age at First Use, and the Annual Incidence

Rates of First Use (Per 1,000 Person-Years of Exposure), by Gender

Year

Number of Initiates

(1,000s) Mean Age at First Use Incidence Rates1

Males Females Males Females Males Females

1965 315 239 18.1 23.4 4.9 3.3

1966 642 333 18.8 19.9 9.8 4.5

1967 952 433 19.1 20.4 14.4 5.7

1968 1,212 527 19.0 20.1 18.1 6.8

1969 1,264 859 18.6 19.5 18.7 10.9

1970 1,479 1,112 18.6 19.0 21.7 13.9

1971 1,570 1,218 18.4 19.0 22.9 15.1

1972 1,560 1,258 19.2 18.3 22.7 15.5

1973 1,587 1,267 18.6 18.6 23.1 15.5

1974 1,493 1,360 17.7 18.1 21.7 16.6

1975 1,405 1,469 17.7 18.9 20.4 17.8

1976 1,625 1,559 18.2 18.8 23.6 18.9

1977 1,647 1,517 18.0 18.5 23.9 18.4

1978 1,556 1,411 17.6 18.7 22.5 17.0

1979 1,507 1,352 17.5 18.7 21.7 16.2

1980 1,187 1,335 19.0 19.4 17.0 15.9

1981 896 971 17.2 18.6 12.6 11.4

1982 1,014 1,007 17.9 19.7 14.1 11.7

1983 1,049 815 18.9 17.4 14.4 9.4

1984 1,020 992 18.3 18.2 13.8 11.3

1985 1,021 844 18.2 17.9 13.6 9.5

1986 925 828 17.8 17.4 12.1 9.2

1987 773 815 17.3 17.9 10.0 9.0

1988 834 716 17.1 17.9 10.8 7.9

1989 787 660 17.5 17.8 10.3 7.3

1990 774 633 17.5 19.4 10.2 7.1

1991 837 648 18.1 17.8 11.2 7.3

1992 909 690 16.6 16.8 12.3 7.8

1993 1,009 945 16.8 17.6 13.8 10.8

1994 1,152 1,035 16.7 16.8 16.0 11.9

1995 1,254 1,103 16.4 16.7 17.7 12.9

1996 1,284 1,306 16.4 17.7 18.5 15.5

1997 1,318 1,176 17.0 16.9 19.3 14.1

1998 1,268 1,220 17.6 17.2 18.9 14.9

19992 1,034 993 16.4 17.6 15.5 12.1 1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
31

Table 3.4 Estimated Annual Age-Gender Specific Incidence Rates of First Use (Per 1,000

Person-Years of Exposure) of Persons Who First Used Marijuana During the

Years 1965 to 1999

Year

Age-Gender Specific Incidence Rates1

Males

12-14

Females

12-14

Males

15-17

Females

15-17

Males

18-20

Females

18-20

Males

21+

Females

21+

1965 7.2 * 21.5 5.9 18.2 16.0 3.0 3.4

1966 11.1 * 30.5 14.7 60.9 22.3 5.8 3.3

1967 19.7 8.8 37.7 17.2 68.0 24.0 12.4 4.1

1968 17.1 6.1 46.9 18.8 125.6 34.0 11.0 5.4

1969 19.1 11.9 71.2 37.4 121.7 49.1 9.6 8.2

1970 30.9 28.6 86.4 57.5 124.6 54.8 11.6 8.2

1971 41.3 32.3 83.0 48.9 125.5 64.1 12.2 10.3

1972 43.6 22.5 99.5 77.0 108.3 64.5 12.8 8.2

1973 43.9 33.5 110.6 68.0 98.2 68.3 11.4 7.5

1974 40.0 42.0 118.6 84.6 89.7 64.1 8.0 7.3

1975 48.3 44.4 99.4 88.5 93.2 58.2 7.2 9.4

1976 34.1 34.0 142.5 109.6 114.5 71.3 9.1 9.5

1977 49.9 44.5 131.6 108.3 117.5 72.6 8.5 7.8

1978 48.4 37.6 141.2 110.5 100.0 81.3 6.6 6.4

1979 57.0 41.6 133.2 106.3 114.3 73.7 4.9 5.8

1980 37.2 29.9 110.3 109.1 66.0 78.0 6.8 6.5

1981 30.9 26.2 82.9 79.7 60.3 54.4 3.2 4.5

1982 36.3 23.7 93.4 83.0 72.3 57.6 4.0 5.2

1983 34.5 26.9 96.2 69.6 58.4 44.9 6.2 2.5

1984 46.5 31.4 90.7 82.2 63.5 53.3 4.0 4.1

1985 38.1 28.8 85.8 79.2 73.7 50.5 5.0 2.2

1986 33.4 26.5 83.6 80.6 67.2 47.5 3.8 2.2

1987 18.5 22.0 80.8 81.6 76.0 50.0 1.8 2.2

1988 29.0 16.7 85.9 71.4 62.2 43.0 2.6 2.4

1989 26.3 19.6 82.9 64.3 51.7 45.3 2.6 1.7

1990 27.2 19.1 79.7 55.3 58.6 34.5 2.3 2.5

1991 31.5 18.6 77.3 62.2 56.5 44.3 3.5 1.7

1992 36.1 29.3 88.3 59.6 70.9 46.6 2.2 1.4

1993 45.6 39.6 90.5 82.5 75.2 57.4 2.6 2.2

1994 49.6 46.8 112.7 89.1 80.5 67.3 2.5 1.9

1995 61.2 49.9 126.8 90.3 76.9 74.6 2.8 2.2

1996 65.1 55.0 127.0 117.8 80.5 80.4 2.8 3.1

1997 60.2 59.2 130.5 110.3 94.0 67.7 2.8 2.1

1998 59.9 58.8 127.4 111.5 83.9 75.2 3.0 2.6

19992 51.8 48.1 112.2 97.9 53.0 52.1 2.3 2.4

* Low precision; no estimate reported.

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
32

Table 3.5 Estimated Numbers (in Thousands) of Persons Who First Used Marijuana

During the Years 1965 to 1999, by Racial/Ethnic Subgroups

Year

Number of Initiates (1,000s)

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 427 * * * * *

1966 804 113 * * * *

1967 1,180 128 49 * * *

1968 1,417 246 62 * * *

1969 1,834 175 63 * * *

1970 2,264 180 73 38 * 21

1971 2,313 228 177 * 14 *

1972 2,413 244 111 12 22 17

1973 2,442 260 91 * * *

1974 2,343 256 213 12 * 19

1975 2,377 296 171 12 * *

1976 2,615 317 172 * 31 *

1977 2,608 277 163 74 * 28

1978 2,370 297 206 77 * 12

1979 2,388 275 127 * 8 23

1980 2,067 235 168 * * *

1981 1,518 195 120 * 6 *

1982 1,640 164 165 * 16 7

1983 1,459 149 187 39 11 *

1984 1,633 232 98 * 8 7

1985 1,437 179 165 65 7 12

1986 1,375 186 130 25 24 13

1987 1,242 140 134 52 10 12

1988 1,222 137 132 20 24 15

1989 1,074 137 183 21 * 16

1990 1,057 144 144 49 8 5

1991 1,092 164 146 50 14 20

1992 1,154 199 178 27 13 27

1993 1,388 256 225 34 23 28

1994 1,582 273 250 41 16 24

1995 1,711 282 259 54 16 35

1996 1,848 303 307 75 19 39

1997 1,733 345 308 44 20 43

1998 1,702 336 320 80 19 31

19991 1,436 248 246 39 30 28

* Low precision; no estimate reported. 1 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
33

Table 3.6 Estimated Mean Ages at First Use of Persons Who First Used Marijuana

During the Years 1965 to 1999, by Racial/Ethnic Subgroups

Year

Mean Age at First Use

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 21.3 * * * * *

1966 19.3 19.2 * * * *

1967 19.7 18.5 22.0 * * *

1968 19.3 19.6 20.2 * * *

1969 19.0 19.0 18.6 * * *

1970 18.9 17.1 17.1 18.0 * *

1971 18.8 18.4 17.9 * * *

1972 18.8 18.0 21.2 * 19.5 *

1973 18.7 18.4 18.0 * * *

1974 17.9 18.4 17.1 * * 16.6

1975 18.5 17.3 18.1 * * *

1976 18.4 19.8 17.7 * 16.8 16.4

1977 18.4 18.0 18.1 17.7 16.6 *

1978 17.9 18.5 20.1 17.9 * *

1979 18.2 17.7 16.7 * 14.5 15.2

1980 19.4 18.8 17.9 17.1 * *

1981 18.0 18.6 15.9 * * *

1982 18.8 20.8 17.0 * 18.1 *

1983 18.2 18.2 18.8 18.5 16.2 14.0

1984 18.0 20.3 14.7 29.5 10.8 13.5

1985 18.2 17.6 17.4 17.1 14.8 19.1

1986 17.8 17.4 16.9 16.1 14.5 14.9

1987 17.7 16.6 17.3 19.2 19.6 18.3

1988 17.4 16.5 18.0 17.9 21.8 15.1

1989 17.9 17.2 17.0 17.3 16.5 15.5

1990 18.6 17.8 17.7 17.5 19.3 14.9

1991 18.3 17.5 16.0 17.7 22.2 16.5

1992 16.8 17.0 15.7 17.5 15.4 16.0

1993 17.1 17.9 16.7 18.1 22.7 14.4

1994 16.8 16.9 16.2 16.5 15.8 15.2

1995 16.5 16.8 16.0 18.3 15.1 14.9

1996 17.1 17.6 16.7 17.3 14.5 16.0

1997 17.0 17.7 16.0 16.6 15.8 15.9

1998 17.8 17.2 16.0 17.6 14.6 17.0

19991 17.2 16.5 16.4 18.8 14.1 15.8

* Low precision; no estimate reported.

1 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
34

Table 3.7 Estimated Annual Incidence Rates of First Use (Per 1,000 Person-Years of

Exposure) of Persons Who First Used Marijuana During the Years 1965 to

1999, by Racial/Ethnic Subgroups

Year

Racial/Ethnic Specific Incidence Rates1

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 4.0 * * * * *

1966 7.5 8.0 * * * *

1967 10.8 8.9 4.1 * * *

1968 12.8 16.7 4.9 * * *

1969 16.4 11.7 4.9 * * *

1970 20.2 11.8 5.4 7.3 * 21.3

1971 20.6 14.7 12.7 * 20.0 *

1972 21.5 15.5 7.7 2.2 31.6 17.7

1973 21.8 16.3 6.2 * * *

1974 21.0 15.9 14.1 2.0 * 18.8

1975 21.3 18.2 11.1 2.0 * *

1976 23.5 19.4 10.9 * 41.5 34.0

1977 23.5 16.8 10.1 11.7 * 27.0

1978 21.4 17.8 12.5 12.2 * 11.6

1979 21.6 16.3 7.5 * 10.3 21.3

1980 18.6 13.7 9.7 * * *

1981 13.5 11.1 6.8 * * *

1982 14.5 9.1 9.2 * 19.7 5.8

1983 12.8 8.1 10.1 5.7 14.1 *

1984 14.2 12.4 5.2 * 9.3 5.5

1985 12.4 9.4 8.6 9.1 8.0 9.2

1986 11.7 9.6 6.6 3.4 28.5 9.2

1987 10.5 7.1 6.7 7.0 11.4 8.2

1988 10.3 6.9 6.5 2.7 28.8 10.3

1989 9.2 6.9 9.1 2.9 * 10.9

1990 9.1 7.3 7.3 6.6 10.2 3.4

1991 9.5 8.4 7.4 6.9 16.9 13.9

1992 10.1 10.3 9.1 3.7 17.1 19.5

1993 12.3 13.4 11.6 4.7 29.3 20.9

1994 14.2 14.5 13.1 5.7 21.8 18.3

1995 15.6 15.2 13.7 7.6 21.2 27.1

1996 17.1 16.6 16.5 10.5 25.8 31.2

1997 16.3 19.2 16.8 6.2 28.8 35.4

1998 16.3 19.1 17.8 11.6 28.6 26.2

19992 13.8 14.0 13.5 5.6 46.5 26.4

* Low precision; no estimate reported.

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
35

4. State Incidence Estimates

4.1 Introduction

This chapter summarizes estimates of recent marijuana initiation (new use in the past 24

months) for the 50 States and the District of Columbia based on the combined data from the

1999 and 2000 National Household Surveys on Drug Abuse (NHSDAs). These estimates were

derived from a model that used a large number of variables and data collected from each State

and the District of Columbia. Note that State-level incidence estimates reported in this chapter

are different from those of the other chapters. That is, the State-level estimates in this chapter are

referred to as the average annual marijuana initiates over the past 24 months prior to the NHSDA

interview. They are presented by the following age groupings: 12 to 17 years, 18 to 25 years, 26

years or older, and a combined total for all ages 12 or older. For more information about the

methodology used to generate State-level estimates of substance use, refer to State Estimates of

Substance Use from the 2000 NHSDA (Wright, in press).

4.2 State-Level Estimates of Recent New Marijuana Users

Table 4.1 displays estimated numbers of the average annual marijuana initiates over the

past 24 months by age group and State. Also included in the table are their corresponding 95

percent prediction intervals that indicate the precision of the estimates. The prediction interval

reflects the uncertainty associated with sampling variability and model bias. There is a 95

percent probability that the true value lies within the interval.

Overall, the combined 1999 and 2000 NHSDAs estimated that there were approximately

2.3 million recent new marijuana users annually. On average, there were an estimated 1.2

million recent marijuana initiates aged 12 to 17 annually, 0.9 million recent initiates aged 18 to

25 , and 0.1 million recent initiates aged 26 or older. These averaged annual numbers of recent

new marijuana users varied by States.

Estimated average annual rates of first use of marijuana over the past 24 months and

associated 95 percent prediction intervals, by age group and State, are summarized in Table 4.2.

Among all persons aged 12 or older, there were an estimated 1.5 marijuana initiates per 1,000

potential new users annually. The average annual incidence rate was about the same for youths

aged 12 to 17 (6.1) and young adults aged 18 to 25 (5.5), while it was very low (0.1) among

adults aged 26 or older.

The average annual incidence rates varied slightly across different individual States, and

the pattern of distributions also differed by age group. This chapter's figures (maps) display the
36

ranking of these incidence rates by State for all respondents aged 12 or older and for two young

age groups (ages 12 to 17 and ages 18 to 25). The color of each State on the maps indicates how

the State ranks relative to other States. States can fall into one of five groups according to their

ranking. Those States with the highest incidence rate are colored red; those with the lowest

estimates are white. Approximately 10 States are included in each group. In some cases, a group

may contain more or fewer than 10 States because the estimate is the same for 2 or more States

in that group. It should be noted that some prediction intervals around State-level estimates are

fairly sizable, which means that some estimates that appear to be different from each other may

not be statistically significant. In particular, States with lower rates of recent first use tend to

have wider confidence intervals than those with higher rates.

The 10 States with the highest overall rates of recent new marijuana users were as

follows (Figure 4.1):

Alaska,

Colorado,

Delaware,

Massachusetts,

Minnesota,

New Hampshire,

New Mexico,

North Dakota,

Vermont, and

Wisconsin.

The 10 States with the lowest overall rates of recent new marijuana users were Alabama,

Arkansas, Florida, Indiana, Louisiana, New Jersey, New York, Pennsylvania, Virginia, and West

Virginia.

The nine States with the highest rates of recent new marijuana users aged 12 to 17 were

as follows (Figure 4.2):

Arizona,

Colorado,

Delaware,

Hawaii,

Massachusetts,

Nevada,

New Hampshire,

New Mexico, and

Vermont.

The 10 States with the lowest rates of recent marijuana initiates aged 12 to 17 were Alabama,

District of Columbia, Idaho, Louisiana, Mississippi, New Jersey, Pennsylvania, Texas, Utah, and

Virginia.
37

Figure 4.1 Average Annual Incidence of Marijuana Use among Persons Aged 12 or Older:

1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

Figure 4.2 Average Annual Incidence of Marijuana Use among Youths Aged 12 to 17:

1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
38

The 10 States with the highest incidence rates among adults aged 18 to 25 were as

follows (Figure 4.3):

Colorado,

Delaware,

Maine,

Massachusetts,

Michigan,

Minnesota,

Montana,

New Hampshire,

Oregon, and

Vermont.

The 10 States with the lowest incidence rates among adults aged 18 to 25 were Arizona,

Arkansas, California, Florida, Louisiana, Oklahoma, South Carolina, Texas, Utah, and West

Virginia.

Because of a very low rate of recent marijuana initiation among adults aged 26 or older,

the distribution of State-level estimates is not shown in a figure.

Figure 4.3 Average Annual Incidence of Marijuana Use among Young Adults Aged 18 to

25: 1999 and 2000

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
39

These average annual incidence rates varied slightly across different States and age

groups. Across different age groups, only a few States were consistently found to be in the

highest or lowest category of recent initiation. Colorado, Delaware, Massachusetts, New

Hampshire, and Vermont were ranked in the top 10 for the overall age group, the youth age

group, and the young adult age group. New Mexico had the highest rate for the overall and youth

age groups. Minnesota had the highest rate for the overall and young adult age groups. By

comparison, Louisiana had the lowest rate of recent new users for the overall, youth, and young

adult age groups. In addition, Texas and Utah had the lowest rates of recent initiation among

youths and young adults.
40

Table 4.1 Estimated Numbers (in Thousands) of Average Annual Marijuana Initiates, by Age Group an

2000 

State

Total

Age Group (Years)

12-17 18-25 

Estimate

Prediction

Interval Estimate

Prediction

Interval Estimate

Prediction

Interval Esti

Total 2,268 1,230 898 1Alabama 34 (29 - 39) 17 (13 - 21) 15 (12 - 19) Alaska 6 (5 - 7) 4 (3 - 4) 2 (2 - 3) Arizona 45 (39 - 52) 29 (24 - 35) 13 (10 - 17) Arkansas 21 (18 - 24) 11 (9 - 14) 8 (6 - 10) California 246 (226 - 267) 135 (123 - 148) 93 (79 - 109) Colorado 38 (32 - 44) 22 (18 - 27) 14 (10 - 18) Connecticut 26 (22 - 30) 15 (12 - 18) 10 (7 - 12) Delaware 7 (6 - 8) 4 (4 - 5) 3 (2 - 3) District of Columbia 4 (4 - 5) 2 (2 - 3) 2 (1 - 2) Florida 105 (95 - 115) 59 (53 - 67) 38 (32 - 44) Georgia 65 (56 - 74) 33 (28 - 39) 28 (22 - 35) Hawaii 10 (8 - 11) 6 (5 - 7) 3 (2 - 4) Idaho 11 (10 - 13) 6 (5 - 7) 5 (4 - 7) Illinois 99 (90 - 108) 53 (47 - 60) 40 (34 - 46) Indiana 49 (42 - 56) 26 (22 - 32) 19 (15 - 24) Iowa 26 (22 - 29) 14 (11 - 17) 10 (8 - 13) Kansas 25 (22 - 29) 13 (11 - 16) 11 (9 - 14) Kentucky 37 (32 - 42) 19 (16 - 23) 16 (13 - 19) Louisiana 36 (31 - 42) 20 (17 - 25) 13 (10 - 17) Maine 11 (10 - 13) 6 (5 - 7) 4 (3 - 6) Maryland 42 (36 - 48) 21 (17 - 26) 18 (14 - 22) Massachusetts 60 (51 - 68) 36 (30 - 43) 20 (15 - 26) Michigan 92 (84 - 101) 51 (46 - 57) 36 (31 - 42) Minnesota 48 (42 - 55) 24 (20 - 28) 22 (18 - 27) Mississippi 25 (21 - 29) 12 (10 - 15) 11 (9 - 14) Missouri 46 (40 - 53) 25 (20 - 30) 19 (15 - 24) Montana 9 (8 - 10) 5 (4 - 6) 3 (3 - 4) 
Table 4.1 (continued)

State

Total

Age Group (Years)

12-17 18-25 

Estimate

Prediction

Interval Estimate

Prediction

Interval Estimate

Prediction

Interval Esti

41

Nebraska 15 (13 - 17) 8 (6 - 10) 6 (5 - 8) Nevada 15 (13 - 17) 9 (7 - 11) 5 (4 - 6) New Hampshire 11 (10 - 13) 7 (5 - 8) 4 (3 - 5) New Jersey 64 (55 - 74) 31 (25 - 37) 29 (22 - 37) New Mexico 18 (15 - 21) 11 (9 - 13) 6 (5 - 8) New York 144 (130 - 159) 73 (65 - 83) 62 (52 - 72) North Carolina 65 (56 - 74) 38 (32 - 44) 23 (18 - 29) North Dakota 7 (6 - 8) 4 (3 - 5) 3 (2 - 4) Ohio 94 (85 - 102) 50 (44 - 56) 39 (33 - 45) Oklahoma 28 (24 - 33) 17 (14 - 21) 9 (7 - 12) Oregon 28 (24 - 33) 15 (12 - 18) 12 (9 - 15) Pennsylvania 92 (83 - 101) 46 (41 - 52) 40 (34 - 46) Rhode Island 9 (8 - 10) 5 (4 - 6) 3 (2 - 4) South Carolina 32 (27 - 37) 18 (15 - 22) 12 (9 - 15) South Dakota 7 (6 - 8) 4 (3 - 5) 3 (2 - 4) Tennessee 47 (40 - 54) 26 (21 - 31) 19 (14 - 24) Texas 168 (153 - 184) 90 (81 - 101) 67 (58 - 78) Utah 20 (17 - 24) 10 (8 - 13) 9 (7 - 11) Vermont 6 (5 - 7) 4 (3 - 4) 2 (2 - 3) Virginia 53 (45 - 61) 26 (21 - 31) 23 (18 - 30) Washington 49 (43 - 57) 28 (23 - 33) 18 (14 - 23) West Virginia 14 (12 - 17) 8 (6 - 9) 6 (5 - 7) Wisconsin 53 (46 - 60) 30 (26 - 35) 20 (16 - 25) Wyoming 5 (4 - 6) 3 (2 - 3) 2 (2 - 2) Note:Estimates are based on a survey-weighted hierarchical Bayes estimation approach, and the 95 percent prediction (credible) intervals are genera

Carlo techniques.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
42

Table 4.2 Average Annual Rates of First Use of Marijuana, by Age Group and State: 1999 and 2000State

Total

Age Group (Years)

12-17 18-25 

Estimate

Prediction

Interval Estimate

Prediction

Interval Estimate

Prediction

Interval Est

Total 1.52 6.08 5.47 Alabama 1.28 (1.08 - 1.51) 5.19 (4.09 - 6.56) 5.35 (4.18 - 6.81) Alaska 2.32 (1.96 - 2.74) 7.29 (5.96 - 8.89) 6.48 (4.95 - 8.46) Arizona 1.82 (1.54 - 2.15) 8.16 (6.69 - 9.92) 4.69 (3.53 - 6.19) Arkansas 1.32 (1.12 - 1.55) 5.75 (4.65 - 7.09) 4.58 (3.58 - 5.84) California 1.46 (1.33 - 1.61) 5.57 (5.05 - 6.15) 4.50 (3.83 - 5.29) Colorado 2.01 (1.69 - 2.40) 7.68 (6.19 - 9.47) 7.03 (5.34 - 9.20) Connecticut 1.59 (1.32 - 1.92) 6.83 (5.45 - 8.53) 6.47 (4.84 - 8.60) Delaware 1.90 (1.61 - 2.24) 8.32 (6.83 - 10.10) 7.01 (5.33 - 9.17) District of Columbia 1.48 (1.24 - 1.77) 5.54 (4.34 - 7.05) 5.28 (4.06 - 6.83) Florida 1.21 (1.09 - 1.34) 5.76 (5.06 - 6.55) 4.67 (3.96 - 5.50) Georgia 1.50 (1.28 - 1.76) 5.61 (4.67 - 6.71) 5.47 (4.25 - 7.00) Hawaii 1.65 (1.38 - 1.97) 7.63 (6.16 - 9.41) 5.50 (4.01 - 7.50) Idaho 1.58 (1.33 - 1.87) 4.91 (3.93 - 6.11) 5.39 (4.20 - 6.88) Illinois 1.56 (1.41 - 1.73) 6.17 (5.45 - 6.97) 5.61 (4.80 - 6.55) Indiana 1.44 (1.23 - 1.69) 5.88 (4.82 - 7.15) 5.27 (4.11 - 6.74) Iowa 1.47 (1.26 - 1.73) 6.17 (5.03 - 7.56) 5.24 (4.11 - 6.66) Kansas 1.68 (1.42 - 1.98) 6.17 (4.96 - 7.64) 6.54 (5.12 - 8.32) Kentucky 1.62 (1.39 - 1.89) 6.74 (5.52 - 8.21) 6.46 (5.15 - 8.06) Louisiana 1.39 (1.18 - 1.65) 5.51 (4.49 - 6.75) 4.26 (3.25 - 5.55) Maine 1.74 (1.47 - 2.05) 7.12 (5.81 - 8.70) 8.07 (6.17 - 10.48) Maryland 1.52 (1.28 - 1.81) 5.92 (4.77 - 7.32) 6.14 (4.80 - 7.84) Massachusetts 2.03 (1.71 - 2.41) 8.75 (7.17 - 10.65) 7.55 (5.73 - 9.88) Michigan 1.83 (1.66 - 2.03) 7.10 (6.31 - 7.98) 6.90 (5.88 - 8.07) Minnesota 1.91 (1.63 - 2.24) 6.42 (5.24 - 7.84) 7.63 (6.05 - 9.59) Mississippi 1.49 (1.27 - 1.76) 5.26 (4.22 - 6.54) 5.32 (4.22 - 6.69) Missouri 1.51 (1.28 - 1.79) 5.85 (4.76 - 7.17) 5.91 (4.60 - 7.56) Montana 1.73 (1.48 - 2.03) 7.33 (5.98 - 8.96) 6.58 (5.17 - 8.34) 
Table 4.2 (continued)

State

Total

Age Group (Years)

12-17 18-25 

Estimate

Prediction

Interval Estimate

Prediction

Interval Estimate

Prediction

Interval Est

43

Nebraska 1.51 (1.29 - 1.77) 5.71 (4.63 - 7.03) 5.48 (4.29 - 6.98) Nevada 1.66 (1.39 - 1.98) 7.63 (6.18 - 9.37) 5.47 (4.07 - 7.32) New Hampshire 1.92 (1.62 - 2.27) 7.52 (6.16 - 9.15) 7.49 (5.65 - 9.88) New Jersey 1.39 (1.18 - 1.64) 5.50 (4.53 - 6.67) 6.45 (4.96 - 8.33) New Mexico 1.99 (1.68 - 2.35) 7.66 (6.24 - 9.37) 5.99 (4.54 - 7.86) New York 1.43 (1.28 - 1.59) 5.64 (4.94 - 6.44) 5.93 (5.01 - 7.00) North Carolina 1.50 (1.28 - 1.75) 6.67 (5.59 - 7.94) 5.35 (4.16 - 6.86) North Dakota 1.89 (1.64 - 2.19) 7.31 (6.04 - 8.81) 6.53 (5.21 - 8.17) Ohio 1.49 (1.35 - 1.65) 5.94 (5.25 - 6.72) 5.91 (5.09 - 6.86) Oklahoma 1.47 (1.24 - 1.76) 6.58 (5.26 - 8.20) 4.14 (3.16 - 5.41) Oregon 1.70 (1.42 - 2.03) 6.50 (5.27 - 7.99) 7.10 (5.48 - 9.14) Pennsylvania 1.32 (1.19 - 1.46) 5.32 (4.71 - 5.99) 5.85 (5.03 - 6.79) Rhode Island 1.69 (1.43 - 1.99) 7.34 (5.95 - 9.03) 6.57 (5.01 - 8.56) South Carolina 1.47 (1.25 - 1.74) 6.43 (5.24 - 7.87) 4.95 (3.82 - 6.39) South Dakota 1.60 (1.37 - 1.88) 6.16 (5.02 - 7.53) 5.43 (4.22 - 6.96) Tennessee 1.49 (1.26 - 1.76) 6.34 (5.17 - 7.76) 5.46 (4.22 - 7.03) Texas 1.47 (1.33 - 1.63) 5.49 (4.88 - 6.18) 4.55 (3.89 - 5.30) Utah 1.60 (1.34 - 1.91) 4.67 (3.71 - 5.87) 3.88 (3.00 - 5.02) Vermont 2.25 (1.91 - 2.66) 8.30 (6.89 - 9.98) 8.22 (6.33 - 10.61) Virginia 1.40 (1.17 - 1.66) 5.09 (4.15 - 6.23) 5.68 (4.35 - 7.39) Washington 1.61 (1.37 - 1.90) 6.78 (5.58 - 8.21) 5.17 (3.99 - 6.66) West Virginia 1.28 (1.09 - 1.50) 6.27 (5.10 - 7.70) 4.98 (3.86 - 6.41) Wisconsin 1.88 (1.61 - 2.19) 7.34 (6.15 - 8.74) 6.46 (5.03 - 8.28) Wyoming 1.83 (1.56 - 2.14) 6.51 (5.33 - 7.94) 6.18 (4.84 - 7.86) Note:Estimates are based on a survey-weighted hierarchical Bayes estimation approach, and the 95 percent prediction (credible) intervals are genera

Carlo techniques.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
44
45

5. Characteristics of Recent Marijuana Initiates

5.1 Prior Research

This chapter presents findings on (a) the demographic and prior substance use

characteristics of recent marijuana initiates (i.e., 1998 and 1999 marijuana initiates), (b) the

seasonality of incidence, and (c) potential predictors of marijuana initiation. These data provide

descriptive information about young people who have recently initiated use of marijuana. This

information can suggest potential approaches to prevention efforts and may also indicate issues

that deserve further research to more fully understand the underlying factors involved in

marijuana initiation.

Little prior research has been conducted on the characteristics and predictors of

marijuana initiation. Most research on correlates has focused on use, not initiation. Factors

associated with marijuana initiation include individuals' personality characteristics, adverse

family factors, lower level of parental attachment, low parental monitoring, parental substance

use, and peers' influences (Bailey & Hubbard, 1990; Brook et al., 1998a; Chilcoat & Anthony,

1996; Kandel, Griesler, Davies, & Schaffsan, 2001; Van Etten & Anthony, 1999).

Rates of first marijuana use also are influenced by demographic characteristics and by

prior use of licit substances. Male youths tended to initiate marijuana use earlier than female

youths (Kandel & Logan, 1984; Warren et al., 1997). However, younger cohorts of females

appeared to initiate marijuana at earlier ages than older cohorts (Warren et al., 1997). Onset of

marijuana use was also strongly correlated with age. The rate of marijuana initiation remained

relatively flat up to about 13 years of age and increased over the succeeding 5 years (Kosterman

et al., 2000). First use of marijuana rarely occurred after age 21, with the period of highest risk

peaking at around age 17 and declining sharply thereafter (Kandel & Logan, 1984; Kandel &

Yamaguchi, 1985).

In addition, the use of licit substances, such as cigarettes and alcohol, has been suggested

to play a role in marijuana initiation. Studies have found that alcohol and/or tobacco tended to

precede the use of marijuana, which in turn was followed by the use of other illicit or hard drugs

(Duncan, Duncan, & Hops, 1998; Ellickson et al., 1992; Fleming, Leventhal, Glynn, & Ershler,

1989; Kandel et al., 1992; Kandel & Yamaguchi, 1985; Yamaguchi & Kandel, 1984). Both

current and prior use of marijuana was found to influence the initiation of other illicit drugs

among men and women (Kandel & Yamaguchi, 1985).

Research on the developmental sequence of substance use has suggested that gateway

drug use may not be generalized to all substance users. An increasing number of studies have
46

reported racial/ethnic differences in rates of substance initiation, including marijuana. These

observed differences have been suggested to be associated with different family and/or cultural

factors (Catalano et al., 1992) or with differential availability of substances and parental attitudes

toward substance use (Gillmore et al., 1990). Neumark-Sztainer et al. (1996) found that AfricanAmerican students had a relatively lower prevalence of tobacco use, but a higher prevalence of

marijuana use, than students of other racial/ethnic groups. Gillmore et al. (1990) reported that

initiation rates of gateway drugs differed by race/ethnicity and gender. They found that, among

5th graders, white students reported higher rates of initiation of alcohol and tobacco than black or

Asian students. White and Asian-American females were less likely than their male counterparts

to have engaged in substance use; however, black females were more likely than black males to

have used tobacco, alcohol, and marijuana (Gillmore et al., 1990). Recent NHSDA analyses of

youth respondents have identified some significant racial/ethnic differences in factors that might

be associated with substance use (e.g., access to illicit drugs, parental supervision, and religious

beliefs) (Lane et al., 2001).

Similarly, descriptive 1999 NHSDA estimates of persons aged 20 to 25 have suggested

that neither cigarettes nor alcohol appeared to be a compelling trigger for subsequent marijuana

use because there was no fixed pattern of progression from cigarettes or alcohol to marijuana at

the national level (Wright & Davis, 2001). In fact, a large proportion of persons aged 20 to 25

reported never using marijuana, and only one third reported either starting with cigarettes and

going on to marijuana or starting with alcohol then going on to marijuana. Depending on prior

use of a specific substance, the lag between first use of alcohol and first use of marijuana, or

between first use of cigarettes and first use of marijuana, also varied widely (Wright & Davis,

2001).

Prior to this report, there were no data on the seasonality of marijuana initiation. Few

available data suggest a potential seasonality in marijuana use. The analysis of data from reports

of arrests found a seasonal fluctuation, with the highest marijuana arrest rates during the summer

months (peaking in June or July) and the lowest arrest rates in the winter months (Zingraff &

Belyea, 1983). Kovalenko et al. (2000) conducted a cross-sectional study to determine when the

symptoms of marijuana use and other psychiatric disorders were highest over a 12-month period.

They found significant seasonal variations in symptom counts of marijuana use. Symptom

counts of marijuana use reached their nadir in February and March and their zenith in August

and September.

5.2 Characteristics of Recent Marijuana Initiates

The characteristics of 1998 and 1999 marijuana initiates were examined using data from

the 1999 and 2000 surveys. Estimated proportions of recent new marijuana users by gender and
47

race/ethnicity are summarized in Table 5.1. In 1998 and 1999, there were 2.3 million male

initiates and 2.2 million female initiates. For both genders, approximately 70 percent of these

recent new marijuana users were white, 3 percent were Asian or Pacific Islander or Native

Hawaiian, and 1 percent each were American Indian/Alaska Native or persons reporting more

than one race. Of all new male users, 11.7 percent were black, while 14.2 percent of all new

female users were black. In comparison, 14.1 percent of all new male users were Hispanic and

10.8 percent of all new female users were Hispanic.

Overall, only 1.5 percent of all recent new users initiated marijuana use before age 12

and 5.5 percent initiated at age 26 or older (Table 5.1). An increased proportion of recent

initiates was noted between the ages of 13 and 18, ranging from 9 to 15 percent for each age,

then it declined sharply thereafter with increasing age (Figure 5.1). Specifically, 4.4 percent of

new users had started to use marijuana at age 12. The proportion of first-time users jumped to

9.3 percent at age 13 and peaked at age 15 (15.1 percent). It was 14.2 percent at age 16,

decreasing to 11.3 percent at age 17, 9.0 percent at age 18, and 5.0 percent at age 19. A similar

age of initiation pattern was observed for both genders. For males, the highest proportion of all

recent initiates was at ages 15 and 16 (both at 14.8 percent); for females, it was at age 15 (15.4

percent). A slightly higher proportion of male than female initiates started to use marijuana

before age 12 (2.0 vs. 0.9 percent).

Data on the prior use of alcohol and/or cigarettes in relation to gender and age of first

marijuana use among recent marijuana initiates are displayed in Table 5.2. Approximately 60

percent of recent initiates reported prior use of both alcohol and cigarettes. About 9 percent had

never used alcohol or cigarettes in their lifetime, and the remaining recent initiates had used

either alcohol only (16.6 percent) or cigarettes only (14.8 percent) in their lifetime (Figure 5.2).

For both genders, early-onset marijuana users (before age 15) reported a higher proportion of

prior use of cigarettes only than those starting their use at age 15 or older. By comparison, adultonset marijuana users reported a higher proportion of prior use of alcohol only than those

starting their use at a younger age. Early-onset marijuana users were also much more likely than

other initiates to have begun using marijuana prior to any use of cigarettes or alcohol. 

5.3 Seasonality of Incidence

The distribution of month of first marijuana use is presented by gender and age of first

marijuana use (Table 5.3). Overall and for males, the highest peak of recent marijuana initiation

was noted in June and July (Figure 5.3). Approximately 21 percent of all recent initiates or 22

percent of male initiates reported initiating their marijuana use in these 2 months. For females,

the month with the highest proportion of recent initiates was in January (10.0 percent) and July

(10.3 percent), while there was a much lower proportion of initiates in February (5.8 percent).
48

Figure 5.1 Recent Marijuana Initiates, by Age at First Use

Note: Recent initiates are persons who used marijuana for the first time in 1998 or 1999.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

Figure 5.3 shows the overall and gender-specific average number of new marijuana users per day

for each month. On average, there were 3,197 male initiates and 2,989 female initiates per day.

Among males, this number of daily initiates increased to approximately 4,300 in June and July.

Among females, the estimated initiates per day rose to 3,625 in July and 3,519 in January. Of all

recent initiates who started using marijuana before age 18, June (11.6 percent) and July (12.0

percent) also had the most new users, while adult-onset marijuana users tended to have initiated

use in January (10.9 percent), December (9.2 percent), or July (9.1 percent).

5.4 Logistic Regression Models

Data on potential predictors of marijuana initiation provide important information for

prevention and treatment interventions. This section reports the findings about suspected

predictors of recent marijuana initiation (defined as first use in 1998 for the 1999 NHSDA and 
49

Figure 5.2 Prior Alcohol and Cigarette Use among Recent Marijuana Initiates, by Gender

Note: Recent initiates are persons who used marijuana for the first time in 1998 or 1999.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

first use in 1999 for the 2000 NHSDA). Logistic regression procedures were used to determine

the relationship between prior use of alcohol and/or cigarettes and marijuana initiation among

persons aged 12 to 25 years (age on January 1st). The analysis sample included persons in the

1999 NHSDA who had never used marijuana as of January 1, 1998, and persons in the 2000

NHSDA who had never used marijuana as of January 1, 1999. Of this sample, 5.6 percent

(weighted estimate) initiated marijuana use within 1 year (i.e., by December 31th, 1998, in the

1999 sample and by December 31th, 1999, in the 2000 sample).

Prior cigarette use, alcohol use, and daily cigarette use were examined as predictors of

marijuana initiation during a 1-year period. Using data about the date of first use, three

categories of onset variables for use of alcohol and cigarettes were defined: (1) initial use at age

13 or younger, (2) initial use at age 14 or older, and (3) no use. The following characteristics

were also included in the logistic regression models: age, gender, race/ethnicity, geographic 
50

Figure 5.3 Estimated Average Number of Marijuana Initiates Per Day for Each Month:

Overall and by Gender

Note: Estimates are based on respondents who gave a substantive response to the month of first use question; hence,

only those respondents who did not require their month of first use to be imputed are included. Initiates are

defined as those respondents whose difference between their current age and age of first using marijuana is

less than 2 years. The average number of initiates per day was calculated by applying the percentage

distribution (Table 5.3) to the estimated number of initiates in 1998 and 1999 (Table 3.1) and adjusting for the

number of days in each month.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

region, and population density. In the model for youths aged 12 to 14, two categories of prior use

of alcohol and/or cigarettes were defined (i.e., ever used vs. never used). In these logistic

regression analyses, age was defined as "age as of January 1, 1998" in the 1999 NHSDA and

"age as of January 1, 1999" in the 2000 NHSDA. Five separate logistic regression models were

reported for five age groups: 12 to 25 years, 12 to 14 years, 15 to 17 years, 18 to 20 years, and 21

to 25 years (Tables 5.4 to 5.8). Schooling status, employment, and marital status were also

examined in the two models for adults aged 18 to 20 and 21 to 25.
51

5.4.1 Results for Persons Aged 12 to 25

Adjusted odds ratios (ORs) of recent marijuana initiation and corresponding 95 percent

confidence intervals (CIs) from a multiple logistic regression analysis of persons aged 12 to 25

are summarized in Table 5.4. The model included age, gender, race/ethnicity, region of

residence, population density, and prior use of alcohol or cigarettes (i.e., any cigarette smoking,

daily cigarette smoking, any alcohol use).

Antecedent use of alcohol or cigarettes and all demographics examined in the model

were found to be associated with recent marijuana initiation. Consistent with the literature and

the descriptive analyses, the odds of becoming a new marijuana user were relatively low among

persons aged 21 to 25 compared with those under age 21. Relative to adults aged 21 to 25,

youths aged 17 or younger had particularly increased odds of initiating use (OR = 9.6 for youths

aged 12 to 15; OR = 8.4 for youths aged 15 to 17). In this model, males were only slightly more

likely than females to initiate marijuana use (OR = 1.1). Whites, Hispanics, and Asians or Pacific

Islanders or Native Hawaiians, relative to blacks, had decreased odds of starting to use

marijuana, while American Indians or Alaska Natives were more likely than blacks to do so (OR

= 2.0). There was no significant difference in the odds of marijuana initiation between blacks

and persons reporting more than one race. Persons living in the West were significantly more

likely than those in other U.S. regions to become initiates. Increased rates of new use also were

more likely among persons living in either large or small metropolitan areas than those in

nonmetropolitan areas.

In addition, prior use of alcohol or cigarettes was highly associated with becoming a new

marijuana user. Regardless of onset age, cigarette smokers were an estimated 6 times more likely

than nonsmokers to initiate marijuana use. Alcohol users were an estimated 7 to 9 times more

likely than nonusers to start using marijuana. Daily cigarette smoking was associated with a

twofold increase in risk for marijuana initiation.

5.4.2 Results for Persons Aged 12 to 14

Among youths aged 12 to 14 (Table 5.5), the odds of becoming a new marijuana user

increased with increasing age. Males were an estimated 1.5 times more likely than females to

start using marijuana. Black youths had greater odds of initiation than white youths, but there

were no significant differences between blacks and other racial/ethnic groups. The West relative

to the Northeast and South regions and small metropolitan areas relative to nonmetropolitan

areas had increased rates of marijuana initiation. Antecedent use of cigarettes and alcohol was

highly associated with the risk of onset of marijuana use (OR = 12.0 for any cigarette use, OR =

4.0 for daily cigarette use, and OR = 5.6 for any alcohol use).
52

5.4.3 Results for Persons Aged 15 to 17

Age, as a continuous variable, was associated with decreased risk of marijuana initiation

in the adjusted logistic regression model of youths aged 15 to 17 (Table 5.6). Gender was not

related to marijuana initiation. American Indian or Alaska Native youths had the highest odds of

becoming new marijuana users, and blacks had higher odds than whites and Asians, Pacific

Islanders, or Native Hawaiians. Youths living in the West or metropolitan areas also had

increased odds of becoming new marijuana users. Consistent with the model for youths aged 12

to 14, prior use of alcohol or cigarettes signaled elevated odds of marijuana initiation. Regardless

of the age group of onset, the adjusted ORs of marijuana initiation were around 6.0 for any

alcohol or cigarette use and 2.0 to 3.0 for daily cigarette use.

5.4.4 Results for Persons Aged 18 to 20

Among young adults aged 18 to 20 (Table 5.7), increased age was associated with

decreased risk of marijuana initiation. In this adult age group, education, employment, and

marital status were also included in the logistic regression model. Gender, education,

employment, and region of residence were not found to be associated with marijuana initiation.

Blacks, relative to Hispanics, had increased odds of initiation. Being married was associated

with decreased odds of initiation compared with being never married. Young adults living in

large metropolitan areas were more likely than those in nonmetropolitan areas to initiate

marijuana use. Antecedent use of alcohol or cigarettes increased the risk of recent marijuana

initiation (OR ~ 4.0 for any cigarette use, OR ~ 8.0 for any alcohol use). Onset of daily cigarette

smoking at age 14 or older predicted an onset of marijuana use (OR = 1.9), while onset before

age 14 was not found to be significant.

5.4.5 Results for Persons Aged 21 to 25

Consistent with previous analyses, the risk of marijuana initiation among adults aged 21

to 25 decreased with older age (Table 5.8). In this age group, gender, employment, region of

residence, and population density were not found to be associated with marijuana initiation.

Blacks, relative to whites, Hispanics, or Asians/Pacific Islanders/Native Hawaiians, had

increased odds of initiation. Young adults aged 21 to 25 who attended college had greater odds

of becoming new marijuana users than high school graduates. Married persons had decreased

odds of initiation compared with those who had never been married. Prior use of alcohol or any

cigarette and daily cigarette smoking at age 14 or older predicted increased odds of initiation, but

daily cigarette smoking before age 14 predicted decreased odds of initiation.
53

Table 5.1 Characteristics of Recent Marijuana Initiates

Characteristics

Total Male Female

Number of

Initiates

(1,000s) %

Number of

Initiates

(1,000s) %

Number of

Initiates

(1,000s) %

Total 4,515 100.0 2,302 100.0 2,214 100.0

Race/Ethnicity

White 3,138 69.5 1,587 68.9 1,551 70.1

Black 584 12.9 269 11.7 315 14.2

Hispanic 565 12.5 326 14.1 240 10.8

Asian/Pacific Islander/

Native Hawaiian 120 2.7 61 2.6 59 2.7

American Indian or

Alaska Native 49 1.1 25 1.1 24 1.1

More than one race 60 1.3 35 1.5 25 1.1

Age at First Marijuana

Use

< 12 66 1.5 45 2.0 20 0.9

12 200 4.4 104 4.5 97 4.4

13 422 9.3 240 10.4 182 8.2

14 572 12.7 282 12.2 290 13.1

15 681 15.1 340 14.8 341 15.4

16 642 14.2 341 14.8 301 13.6

17 509 11.3 285 12.4 224 10.1

18 404 9.0 206 8.9 198 9.0

19 225 5.0 102 4.4 124 5.6

20 181 4.0 79 3.4 102 4.6

21 121 2.7 53 2.3 68 3.1

22 83 1.8 35 1.5 49 2.2

23 61 1.3 28 1.2 32 1.5

24 53 1.2 26 1.1 26 1.2

25 46 1.0 26 1.1 20 0.9

26 or older 249 5.5 110 1.8 139 6.3

Note:Recent initiates are persons who used marijuana for the first time in 1998 based on both 1999 and 2000 NHSDA data or

for the first time in 1999 based on 2000 NHSDA data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
54

Table 5.2 Prior Alcohol and Cigarette Use among Recent Marijuana Initiates

Gender and Age of

First Use of

Marijuana

Alcohol and Cigarette Use at Time of Marijuana Initiation

Never Used Alcohol

or Cigarettes in

Lifetime

Used Cigarettes,

But Not Alcohol in

Lifetime

Used Alcohol, But

Not Cigarettes in

Lifetime

Used Both Alcohol

and Cigarettes in

Lifetime

% of Marijuana

Initiates

% of Marijuana

Initiates

% of Marijuana

Initiates

% of Marijuana

Initiates

Total

Total 9.1 14.8 16.6 59.5

< 15 16.5 24.2 13.1 46.2

15-17 9.0 16.4 15.3 59.3

18-20 4.3 6.8 21.2 67.8

21 or older 0.5 1.3 21.6 76.7

Male

Total 9.7 16.5 16.0 57.8

< 15 16.8 26.1 13.7 43.4

15-17 9.9 18.1 14.9 57.1

18-20 3.3 7.0 19.9 69.8

21 or older 0.7 0.9 20.3 78.1

Female

Total 8.5 13.1 17.1 61.3

< 15 16.1 22.1 12.4 49.4

15-17 8.0 14.6 15.7 61.6

18-20 5.3 6.5 22.3 65.9

21 or older 0.3 1.7 22.6 75.5

Note:Recent initiates are persons who used marijuana for the first time in 1998 based on either 1999 or 2000 NHSDA data or

for the first time in 1999 based on 2000 NHSDA data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
55

Table 5.3 Distribution of Month of First Marijuana Use among Persons Aged 12 or

Older

Month

% of Initiates

Total Male Female

Initiating

Marijuana Before

Age 18

Initiating

Marijuana $18

Total 100.0 100.0 100.0 100.0 100.0

January 9.2 8.2 10.0 7.8 10.9

February 7.0 8.3 5.8 6.9 7.1

March 7.6 7.7 7.5 6.7 8.8

April 7.5 6.9 8.0 7.5 7.5

May 7.7 7.7 7.7 7.5 7.9

June 10.0 11.1 9.0 11.6 8.0

July 10.8 11.3 10.3 12.0 9.1

August 8.1 7.5 8.8 8.1 8.2

September 8.0 8.1 7.8 8.9 6.8

October 8.9 8.5 9.4 9.8 7.9

November 7.8 7.2 8.4 7.2 8.6

December 7.4 7.5 7.3 6.0 9.2

Note:Estimates are based on respondents who gave a substantive response to the month of first use question; hence, only

those respondents who did not require their month of first use to be imputed are included. Initiates are defined as those

respondents whose difference between their current age and age of first using marijuana is less than 2 years.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
56

Table 5.4 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons

Aged 12 to 25

Model Covariates

Adjusted Odds

Ratio

95%

Confidence Interval

Age on January 11

Under 15 9.58 (7.76 - 11.82)

15-17 8.40 (6.87 - 10.26)

18-20 3.29 (2.63 - 4.13)

21 or older 1.00 (1.00 - 1.00)

Gender

Male 1.12 (1.03 - 1.22)

Female 1.00 (1.00 - 1.00)

Race/Ethnicity

White 0.65 (0.56 - 0.76)

Black 1.00 (1.00 - 1.00)

Hispanic 0.62 (0.51 - 0.75)

Asian/Pacific Islander/Native Hawaiian 0.56 (0.40 - 0.80)

American Indian or Alaska Native 2.03 (1.25 - 3.29)

More than one race 0.85 (0.55 - 1.32)

Region

Northeast 0.84 (0.72 - 0.98)

Midwest 0.80 (0.69 - 0.92)

South 0.74 (0.64 - 0.85)

West 1.00 (1.00 - 1.00)

Population Density

Large metro 1.30 (1.15 - 1.47)

Small metro 1.29 (1.15 - 1.46)

Nonmetro 1.00 (1.00 - 1.00)

Cigarette Use

Initiation at age 13 or younger 5.58 (4.81 - 6.48)

Initiation at age 14 or older 5.68 (4.90 - 6.60)

Never used 1.00 (1.00 - 1.00)

Daily Cigarette Use

Initiation at age 13 or younger 2.05 (1.71 - 2.46)

Initiation at age 14 or older 1.96 (1.75 - 2.20)

Never used 1.00 (1.00 - 1.00)

Alcohol Use

Initiation at age 13 or younger 7.26 (6.08 - 8.67)

Initiation at age 14 or older 9.00 (7.51 - 10.78)

Never used 1.00 (1.00 - 1.00)

Note:Recent initiation is defined as starting in the calendar year 1998 based on 1999 data or starting in the calendar year 1999

based on 2000 data. 1

Age on January 1st is the respondent's age on January 1, 1998, if the respondent is from 1999 data or January 1, 1999, if the

respondent is from 2000 data.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
57

Table 5.5 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons

Aged 12 to 14

Model Covariates

Adjusted Odds

Ratio

95%

Confidence Interval

Age on January 11 1.30 (1.14 - 1.48)

Gender

Male 1.47 (1.20 - 1.79)

Female 1.00 (1.00 - 1.00)

Race/Ethnicity

White 0.56 (0.41 - 0.78)

Black 1.00 (1.00 - 1.00)

Hispanic 1.08 (0.71 - 1.64)

Asian/Pacific Islander/Native Hawaiian 0.67 (0.24 - 1.86)

American Indian or Alaska Native 3.08 (0.98 - 9.71)

More than one race 0.55 (0.26 - 1.17)

Region

Northeast 0.68 (0.48 - 0.96)

Midwest 0.76 (0.56 - 1.02)

South 0.63 (0.47 - 0.86)

West 1.00 (1.00 - 1.00)

Population Density

Large metro 1.12 (0.86 - 1.47)

Small metro 1.61 (1.25 - 2.08)

Nonmetro 1.00 (1.00 - 1.00)

Cigarette Use

Ever used 12.00 (8.50 - 16.94)

Never used 1.00 (1.00 - 1.00)

Daily Cigarette Use

Ever used 3.95 (2.91 - 5.36)

Never used 1.00 (1.00 - 1.00)

Alcohol Use

Ever used 5.55 (4.02 - 7.67)

Never used 1.00 (1.00 - 1.00)

Note:Recent initiation is defined as starting in the calendar year 1998 based on 1999 data or starting in the calendar year 1999

based on 2000 data. 1

Age on January 1st is the respondent's age on January 1, 1998, if the respondent is from 1999 data or January 1, 1999, if the

respondent is from 2000 data.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
58

Table 5.6 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons

Aged 15 to 17

Model Covariates

Adjusted Odds

Ratio

95%

Confidence Interval

Age on January 11 0.90 (0.84 - 0.97)

Gender

Male 1.08 (0.95 - 1.23)

Female 1.00 (1.00 - 1.00)

Race/Ethnicity

White 0.63 (0.51 - 0.79)

Black 1.00 (1.00 - 1.00)

Hispanic 0.79 (0.60 - 1.04)

Asian/Pacific Islander/Native Hawaiian 0.45 (0.27 - 0.75)

American Indian or Alaska Native 2.62 (1.13 - 6.10)

More than one race 1.06 (0.55 - 2.02)

Region

Northeast 0.85 (0.70 - 1.04)

Midwest 0.74 (0.61 - 0.91)

South 0.70 (0.58 - 0.84)

West 1.00 (1.00 - 1.00)

Population Density

Large metro 1.35 (1.14 - 1.59)

Small metro 1.29 (1.10 - 1.51)

Nonmetro 1.00 (1.00 - 1.00)

Cigarette Use

Initiation at age 13 or younger 6.09 (4.99 - 7.42)

Initiation at age 14 or older 6.14 (5.07 - 7.44)

Never used 1.00 (1.00 - 1.00)

Daily Cigarette Use

Initiation at age 13 or younger 2.16 (1.66 - 2.81)

Initiation at age 14 or older 3.15 (2.68 - 3.70)

Never used 1.00 (1.00 - 1.00)

Alcohol Use

Initiation at age 13 or younger 6.18 (4.91 - 7.77)

Initiation at age 14 or older 6.47 (5.21 - 8.03)

Never used 1.00 (1.00 - 1.00)

Note:Recent initiation is defined as starting in the calendar year 1998 based on 1999 data or starting in the calendar year 1999

based on 2000 data. 1

Age on January 1st is the respondent's age on January 1, 1998, if the respondent is from 1999 data or January 1, 1999, if the

respondent is from 2000 data.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
59

Table 5.7 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons

Aged 18 to 20

Model Covariates

Adjusted Odds

Ratio 95% Confidence Interval

Age on January 11 0.73 (0.66 - 0.82)

Gender

Male 1.19 (0.99 - 1.44)

Female 1.00 (1.00 - 1.00)

Race/Ethnicity

White 0.79 (0.55 - 1.12)

Black 1.00 (1.00 - 1.00)

Hispanic 0.49 (0.31 - 0.77)

Asian/Pacific Islander/Native Hawaiian 0.56 (0.29 - 1.07)

American Indian or Alaska Native 1.29 (0.46 - 3.62)

More than one race 0.50 (0.21 - 1.18)

Education

High school dropout 0.89 (0.62 - 1.28)

High school student 0.86 (0.67 - 1.12)

High school graduate 0.85 (0.68 - 1.06)

At least some college 1.00 (1.00 - 1.00)

Employment Status

Not employed 0.96 (0.78 - 1.19)

Employed 1.00 (1.00 - 1.00)

Marital Status

Never married 2.76 (1.48 - 5.15)

Married or previously married 1.00 (1.00 - 1.00)

Region

Northeast 0.81 (0.58 - 1.14)

Midwest 0.87 (0.64 - 1.19)

South 0.85 (0.61 - 1.18)

West 1.00 (1.00 - 1.00)

Population Density

Large metro 1.37 (1.07 - 1.76)

Small metro 1.22 (0.98 - 1.52)

Nonmetro 1.00 (1.00 - 1.00)

Cigarette Use

Initiation at age 13 or younger 3.19 (2.26 - 4.49)

Initiation at age 14 or older 3.95 (3.04 - 5.15)

Never used 1.00 (1.00 - 1.00)

Daily Cigarette Use

Initiation at age 13 or younger 1.32 (0.70 - 2.48)

Initiation at age 14 or older 1.86 (1.51 - 2.30)

Never used 1.00 (1.00 - 1.00)

Alcohol Use

Initiation at age 13 or younger 7.41 (4.08 - 13.44)

Initiation at age 14 or older 8.01 (4.67 - 13.74)

Never used 1.00 (1.00 - 1.00)

Note:Recent initiation is defined as starting in the calendar year 1998 based on 1999 data or starting in the calendar year 1999

based on 2000 data. 1

Age on January 1st is the respondent's age on January 1, 1998, if the respondent is from 1999 data or January 1, 1999, if the

respondent is from 2000 data.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
60

Table 5.8 Adjusted Odds Ratios of Marijuana Initiation Within 1 Year among Persons

Aged 21 to 25

Model Covariates

Adjusted Odds

Ratio 95% Confidence Interval

Age on January 11 0.70 (0.63 - 0.78)

Gender

Male 0.92 (0.70 - 1.21)

Female 1.00 (1.00 - 1.00)

Race/Ethnicity

White 0.52 (0.36 - 0.75)

Black 1.00 (1.00 - 1.00)

Hispanic 0.31 (0.17 - 0.57)

Asian/Pacific Islander/Native Hawaiian 0.43 (0.20 - 0.94)

American Indian or Alaska Native 0.85 (0.19 - 3.91)

More than one race 1.79 (0.57 - 5.64)

Education

Not completed high school2 0.58 (0.33 - 1.01)

High school graduate 0.43 (0.30 - 0.60)

At least some college 1.00 (1.00 - 1.00)

Employment Status

Not employed 1.08 (0.76 - 1.53)

Employed 1.00 (1.00 - 1.00)

Marital Status

Never married 2.13 (1.41 - 3.23)

Married or previously married 1.00 (1.00 - 1.00)

Region

Northeast 0.85 (0.55 - 1.33)

Midwest 0.66 (0.43 - 1.01)

South 0.76 (0.50 - 1.15)

West 1.00 (1.00 - 1.00)

Population Density

Large metro 1.08 (0.77 - 1.51)

Small metro 1.02 (0.73 - 1.42)

Nonmetro 1.00 (1.00 - 1.00)

Cigarette Use

Initiation at age 13 or younger 2.85 (1.69 - 4.81)

Initiation at age 14 or older 2.99 (2.06 - 4.33)

Never used 1.00 (1.00 - 1.00)

Daily Cigarette Use

Initiation at age 13 or younger 0.17 (0.03 - 0.88)

Initiation at age 14 or older 1.50 (1.10 - 2.03)

Never used 1.00 (1.00 - 1.00)

Alcohol Use

Initiation at age 13 or younger 20.82 (4.10 - 105.78)

Initiation at age 14 or older 29.27 (6.46 - 132.71)

Never used 1.00 (1.00 - 1.00)

Note:Recent initiation is defined as starting in the calendar year 1998 based on 1999 data or starting in the calendar year 1999

based on 2000 data. 1

Age on January 1st is the respondent's age on January 1, 1998, if the respondent is from 1999 data; or January 1, 1999, if the

respondent is from 2000 data.

2

 Includes high school students and dropouts.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
61

6. Early Marijuana Use and Later Drug Use Patterns

6.1 Introduction

In addition to providing useful information for prevention planning, incidence data can

be used to help policymakers anticipate future trends in the nature and extent of the need for

substance abuse treatment services. Marijuana incidence data have been used to make

projections of drug abuse treatment need in the year 2020 (Gfroerer & Epstein, 1999). That study

and others have shown the importance of early marijuana use as a predictor of later substance

use patterns and associated problems (Brook, Gordon, Brook, & Cohen, 1989; Brook, Cohen, &

Brook, 1998b; Brook et al., 1999b; DeWit, Hance, Offord, & Ogborne, 2000; Grant & Dawson,

1998). Given the substantial increases in marijuana incidence rates during the 1990s and the

continuing high rates as recently as 1999, data showing the relationship between early initiation

and later substance use patterns are needed. This chapter provides such data, primarily focusing

on age at first use of marijuana as a predictor.

The remainder of this chapter focuses on three topics. Section 6.2 discusses the estimated

proportions of drug use patterns among adults aged 26 or older by age at first marijuana use and

by age groups. Section 6.3 provides adjusted odds ratios (ORs) of illicit drug use, heavy illicit

drug use, and substance dependence/abuse from the multiple logistic regression models. Each

logistic regression model includes age of marijuana initiation, age group, gender, race/ethnicity,

and educational level. Section 6.4 includes findings for a subset of the analysis focusing on past

year marijuana users aged 26 or older. This subset examined the relationship between age at first

marijuana use and past year drug dependence (e.g., marijuana dependence, illicit drug

dependence other than marijuana, illicit drug dependence, alcohol dependence or abuse, and

alcohol or illicit drug dependence/abuse).

Heavy marijuana use was defined as using marijuana on at least 300 days in the past

year. Heavy illicit drug use other than marijuana was defined as using at least one of the

following: cocaine (including crack), heroin, hallucinogens (including LSD and PCP), inhalants,

or any prescription-type psychotherapeutic used nonmedically on at least 50 days in the past

year, regardless of marijuana/hashish use. Marijuana/hashish users who also had used any of the

other listed drugs on at least 50 days in the past year were counted as heavy users of illicit drugs

other than marijuana. Because of changes in the measures of dependence and abuse in the 2000

survey, estimates for alcohol or illicit drug abuse and dependence were based only on data from

the 2000 survey. In brief, the 2000 NHSDA includes a series of questions on dependence that

assess health or emotional problems, attempts to cut down on use, tolerance, withdrawal, and

other symptoms associated with substances used. The questions on abuse assess problems at

work, home, and school; problems with family or friends; physical danger; and trouble with the
62

law due to substances used. The changes in measures of abuse and dependence limit the

comparisons between 2000's estimates and estimates from prior surveys.

6.2 Estimated Prevalence of Illicit Drug Use, Heavy Illicit Drug Use,

Substance Abuse, and Dependence, by Age of Marijuana Initiation

6.2.1 Use of Heroin, Cocaine, and Psychotherapeutics Nonmedically

The prevalence of lifetime and past year use of heroin, cocaine, and nonmedical

psychotherapeutics in relation to age at first marijuana use is presented in Table 6.1 and Figure

6.1. Among adults aged 26 or older, the highest prevalence of use of heroin, cocaine, and

psychotherapeutics in the lifetime was noted among those who initiated marijuana before they

were 15 years old (9.2, 62.0, and 53.9 percent, respectively, for heroin, cocaine, and

psychotherapeutics). There was a tendency for the prevalence of lifetime illicit drug use to

decrease with older age of first marijuana use. Among lifetime marijuana users reporting their

onset after age 20, an estimated 1.1 percent used heroin, 16.4 percent used cocaine, and 20.6

percent used any psychotherapeutics nonmedically in their lifetime. Among persons who had

never used marijuana, less than 1 percent had ever used cocaine or heroin, but 5.1 percent had

used psychotherapeutics nonmedically. 

Similar patterns of past year use of these illicit drugs across the four groups of age at first

marijuana use were observed. An estimated 6.9 percent of early-onset marijuana users (onset at

age 14 or younger) used cocaine in the past year compared with only 0.8 percent of those

initiating after age 20. An estimated 11.5 percent of early-onset marijuana users (onset at age 14

or younger) used any psychotherapeutics in the past year, while 2.9 percent of those initiating

after age 20 did so.

For marijuana users aged 26 to 34 and those aged 35 to 49, rates of lifetime illicit drug

use were generally higher among adolescence-onset marijuana users than among users initiating

during adulthood. Because of a low prevalence of other illicit drug use among marijuana users

aged 50 or older and very low proportions of past year heroin use across all three age groups

(less than 1 percent), the relationship between the use of these illicit drugs and the onset age of

marijuana use was less clear for them.

6.2.2 Heavy Illicit Drug Use

Among all lifetime marijuana users aged 26 or older, early-onset users not only had

relatively higher proportions of recent (past year) heavy marijuana use than adult-onset users, 
63

Figure 6.1 Prevalence of Lifetime Use of Heroin, Cocaine, and Psychotherapeutics among

Adults Aged 26 or Older, by Age of Marijuana Initiation: 1999 and 2000

Note: Nonmedical use of any prescription-type psychotherapeutic indicates using pain relievers, tranquilizers,

stimulants, or sedatives at least once. Indicated use does not include over-the-counter drugs.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

but they also reported high proportions of heavy use of other illicit drugs (Table 6.2 and Figure

6.2). An estimated 5.0 percent of those initiating marijuana at age 14 or younger were recent

heavy marijuana users compared with less than 1 percent of those with an onset age of 18 years

or older. Likewise, 6.3 percent of those initiating marijuana at age 14 or younger were recent

heavy users of other illicit drugs in comparison with about 1 percent of those with an onset age

of 18 years or older. A similar pattern also was observed among two age groups of marijuana

users (i.e., adults aged 26 to 34 and those aged 35 to 49). There was an insufficient number of

heavy illicit drug users among the older age group (i.e., aged 50 or older) to allow for such a

comparison. Less than 1 percent of adults who had never used marijuana reported heavy use of

other illicit drugs.
64

Figure 6.2 Prevalence of Past Year Heavy Marijuana Use and Heavy Use of Other Illicit

Drugs among Adults Aged 26 or Older, by Age of Marijuana Initiation: 1999

and 2000

Note: Heavy marijuana use refers to using marijuana on 300 or more days in the past year. Heavy use of other illicit

drugs refers to using cocaine, hallucinogens, inhalants, heroin, or any prescription-type psychotherapeutic

used nonmedically (i.e., pain relievers, sedatives, tranquilizers, or stimulants) on at least 50 days in the past

year.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

6.2.3 Substance Dependence and/or Abuse

The estimated past year prevalence of dependence on and abuse of alcohol or illicit drugs

by age at first use of marijuana is summarized in Table 6.3 and Figure 6.3. Overall and among

those aged 26 to 49, prevalence rates of dependence on or abuse of an illicit drug and prevalence

rates of dependence on or abuse of either alcohol or an illicit drug were highest among those

who started to use marijuana at age 14 or younger. An estimated 6.2 percent of those initiating

marijuana before age 15 abused or were dependent on an illicit drug in the past year compared

with 1.3 percent of those initiating marijuana at age 21 or older. Similarly, 18.0 percent of

early-onset (onset before age 15) marijuana users were classified with dependence on or abuse 
65

Figure 6.3 Prevalence of Past Year Alcohol and/or Illicit Drug Dependence or Abuse

among Adults Aged 26 or Older, by Age of Marijuana Initiation: 2000

Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs:

marijuana/hashish, cocaine (including crack), heroin, hallucinogens (including LSD and PCP), inhalants, or

any prescription-type psychotherapeutic used nonmedically. The alcohol-only data refer to just dependence on

alcohol, not alcohol abuse. Dependence or abuse is based on the definition found in the 4th edition of the

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (APA, 1994).

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.

of either alcohol or an illicit drug in comparison with 7.6 percent of those who first used

marijuana after age 20.

Even when the prevalence was restricted to dependence and was specific to alcohol, an

illicit drug, marijuana, or an illicit drug other than marijuana, prevalence rates of dependence for

each outcome were consistently found to be highest among marijuana users who started their

first use at age 14 or younger.

Among adults who had never used marijuana, the prevalence of past year alcohol and/or

illicit drug abuse or dependence was very low. Only about 0.2 percent of them were classified

with dependence on or abuse of an illicit drug and 0.9 percent were dependent on alcohol. In
66

addition, there was a tendency among those who had never used marijuana for the prevalence of

illicit drug abuse or dependence to be higher among young adults aged 26 to 34 years (0.4

percent), but for the prevalence of alcohol dependence to be slightly higher among persons aged

35 to 49 (1.4 percent).

6.3 Multiple Logistic Regression Models 

The estimated strength of associations of age at first marijuana use with the use of other

illicit drugs and/or recent substance dependence and abuse was determined via multiple logistic

regression procedures. Each logistic regression model also included age, gender, race/ethnicity,

and educational level. Adjusted ORs, denoting the estimated association, that were derived from

the multiple logistic regression procedures are discussed in this section.

6.3.1 Adjusted Odds Ratios of Use of Heroin, Cocaine, and Psychotherapeutics

Nonmedically

Adjusted ORs for use of heroin, cocaine, and psychotherapeutics among lifetime

marijuana users aged 26 or older are displayed in Table 6.4 (lifetime use) and Table 6.5 (past

year use).

6.3.1.1 Heroin

With statistical adjustment for demographic characteristics, age at onset of

marijuana use was significantly associated with lifetime heroin use (Table 6.4). In particular,

onset before age 15 strongly predicted lifetime heroin use. Adjusted ORs of ever using heroin

among lifetime marijuana users were 15.5 for those reporting first marijuana use at age 14 or

younger, 6.1 for those initiating between the ages of 15 and 17, and 3.5 for those initiating

between the ages of 18 and 20 as compared with those experiencing onset at age 21 or older.

Among marijuana users, younger adults were significantly less likely to have ever used heroin

than older adults aged 50 or older (OR = 0.2 for adults aged 26 to 34; OR = 0.5 for adults aged

35 to 49). Male marijuana users were an estimated 1.6 times more likely than female users to

have ever used heroin. Relative to blacks, whites were at lower odds of using heroin in the

lifetime. Educational level was not found to be associated with odds of lifetime heroin use. Age

at first marijuana use was not associated with past year heroin use in the adjusted logistic

regression model (Table 6.5).

6.3.1.2 Cocaine

Age at onset of marijuana use was highly associated with lifetime and recent

cocaine use, particularly for those who initiated before age 15. These persons were 7 to 8 times
67

more likely than those who initiated at age 21 or older to use cocaine (Tables 6.4 and 6.5).

Lifetime marijuana users who were male and American Indian or Alaska Native (relative to

black) also had increased rates of lifetime cocaine use. The analysis of recent cocaine use found

that male gender and less than a high school education predicted increased odds of using cocaine

in the past year (Table 6.5). In addition, white and Asian/Pacific Islander/Native Hawaiian

lifetime marijuana users were less likely than black users to use cocaine recently.

6.3.1.3 Psychotherapeutics

Early onset of marijuana use also predicted increased odds of nonmedical use of

any psychotherapeutic drug in the lifetime and past year (OR = 5.3 for lifetime use; OR = 3.4 for

past year use). Younger adult marijuana users (aged 26 to 34) were less likely than older users

(aged 50 or older) to report using psychotherapeutics in the lifetime, but they were significantly

more likely to use them in the past year. Male marijuana users had decreased odds of using

psychotherapeutics in the past year (OR = 0.8). Compared with black marijuana users, white,

Hispanic, and American Indian/Alaska Native users had increased odds of recent

psychotherapeutic use. Persons with less than high school schooling also had an increased

likelihood of using psychotherapeutics in the past year.

6.3.2 Adjusted Odds Ratios of Heavy Illicit Drug Use

Adjusted ORs of past year (recent) heavy illicit drug use (marijuana and other illicit

drugs) are summarized in Table 6.6. Early-onset of marijuana use (before age 15) was

significantly associated with the increased odds of heavy use of marijuana (OR = 5.3) and other

illicit drugs (OR = 4.5). Marijuana initiation between the ages of 15 and 17 also predicted heavy

use of other illicit drugs (OR = 2.1). Male marijuana users were an estimated 2.1 times more

likely than female users to report heavy marijuana in the past year. Lifetime marijuana users who

did not attend college also were at increased odds of using an illicit drug heavily in the past year.

6.3.3 Adjusted Odds Ratios of Substance Dependence and/or Abuse

This section includes results of multiple logistic regression analyses of the following

outcomes in relation to age at first use of marijuana among lifetime marijuana users aged 26 or

older (Tables 6.7 to 6.9): (1) illicit drug dependence or abuse, (2) alcohol or illicit drug

dependence or abuse, (3) alcohol dependence, (4) illicit drug dependence, (5) marijuana

dependence, and (6) other illicit drug dependence.

Onset of marijuana use before age 15 significantly predicted increased odds of meeting

the criteria for dependence on and/or abuse of either alcohol and/or an illicit drug in the past year

(OR = 4.7 for an illicit drug; OR = 1.9 for alcohol or other illicit drugs). Black marijuana users
68

had an increased likelihood of being dependent on or abusing an illicit drug than white and

Asian/Pacific Islander/Native Hawaiian users. Less educated lifetime marijuana users (less than

high school) were an estimated 1.8 times more likely to be classified with dependence on or

abuse of an illicit drug recently, while age and gender were not associated with any odds of

being dependent on or abusing illicit drugs (Table 6.7). Lifetime marijuana users who were aged

26 to 34, male, or had not attended college at the time of the survey had slightly increased odds

of being dependent on or abusing alcohol or an illicit drug in the past year.

Adjusted ORs of alcohol dependence and illicit drug dependence among lifetime

marijuana users are shown in Table 6.8. Age at marijuana initiation, age, and race/ethnicity were

not found to predict recent alcohol dependence. In comparison, male and less educated

marijuana users were at increased odds of being alcohol dependent in the past year. When the

outcome of the logistic regression model was specific to illicit drug dependence, early-onset

marijuana users (before age 15) were an estimated 6.2 times more likely than adult-onset users to

be dependent on one or more illicit drugs in the past year. Relative to black marijuana users,

white, Asian/Pacific Islander/Native Hawaiian, and American Indian or Alaska Native users had

decreased odds of being classified with illicit drug dependence.

Table 6.9 further examines the estimated association between the onset age of marijuana

use and recent illicit drug dependence. The multiple regression procedures revealed that the

onset of marijuana use before age 15 was associated with recent dependence on both marijuana

and other illicit drugs. In fact, onset before age 15 was associated with close to a tenfold excess

in the odds of being classified with marijuana dependence than those who initiated marijuana in

adulthood, independent of the influences of age, gender, race/ethnicity, and educational level.

Marijuana users with less than a high school education were 3 times more likely than those who

had attended college to be dependent on other illicit drugs recently.

6.4 Substance Dependence and/or Abuse Among Past Year Marijuana

Users

This section focuses on dependence on and abuse of substances among lifetime

marijuana users aged 26 or older who also used marijuana in the past year. The analyses

presented in Section 6.3 demonstrate a high correlation between age at first marijuana use and

subsequent patterns of substance use among adults aged 26 or older. Early-onset marijuana users

are clearly more likely than adult-onset users to use drugs heavily and to have dependence and

abuse problems later in life. However, these results do not indicate whether the higher rate of

problematic use is simply because early-onset users are more likely to continue using illicit

drugs as they age, making them more susceptible to problems, or whether their use of marijuana

at a young age is a predictor of problematic use independent of their use history. Although it is

not possible to fully explore this question with the limited data available in the NHSDA on drug
69

use history, some indication of the independent effect of age at first use can be obtained by

restricting analyses to persons who used marijuana in the past year.

6.4.1 Estimated Prevalence of Illicit Drug Dependence and/or Abuse, by Age of

Marijuana Initiation

Table 6.10 displays past year prevalence of illicit drug dependence or abuse, alcohol or

illicit drug dependence or abuse, and specific substance dependence among past year marijuana

users aged 26 or older. These prevalence estimates are presented by age of marijuana initiation

(14 or younger, 15 to 17 years, 18 to 20 years, and 21 or older).

The highest prevalence of illicit drug dependence or abuse, alcohol or illicit drug

dependence or abuse, marijuana dependence, and other illicit drug dependence was found among

those in the youngest group of age of first marijuana use. Among past year marijuana users, one

fifth of those initiating marijuana before age 15 were classified with illicit drug dependence or

abuse in the past year compared with approximately one tenth of those initiating marijuana after

age 15. Similarly, about 40 percent of those with their onset of marijuana before age 14 met the

criteria for dependence on or abuse of either alcohol or other illicit drugs compared with 16.7

percent of those with an onset after age 20. 

With respect to alcohol dependence, approximately 10 percent of users with an onset of

marijuana use before age 21 were dependent on alcohol in comparison with about 5 percent of

those with an onset after age 20. The highest prevalence (15.2 percent) of illicit drug dependence

was noted among those initiating use before age 15, while the lowest prevalence (3.4 percent) of

illicit drug dependence was among those reporting their first use after age 20. Approximately 8

percent of those with an onset between ages 15 and 20 were dependent on an illicit drug.

Only 2.1 percent of those with their onset of marijuana after age 20 were dependent on

marijuana in the past year, while 8.8 percent of those within the 14 or younger group, 4.7 percent

of those within the 15 to 17 onset group, and 7.1 percent of those within the 18 to 20 onset group

were dependent on marijuana. The prevalence of other illicit drug dependence decreased with

increased age strata of first marijuana use. An estimated 8.6 percent of those with an onset

before age 15 and 4.2 percent of those with an onset between the ages of 15 and 17 were

dependent on other illicit drugs in the past year, while less than 3.0 percent of those with an

onset at age 18 or older were classified with other illicit drug dependence.

6.4.2 Adjusted Odds Ratios of Substance Dependence and/or Abuse

The association between age at first use of marijuana and substance dependence and/or

abuse among past year marijuana users aged 26 or older was examined using multiple logistic
70

regression procedures. Adjusted ORs denote the estimated strength, holding constant the

potential confounding influence of other demographic characteristics. Table 6.11 summarizes the

logistic regression models for two dependence/abuse outcomes: (a) illicit drug dependence or

abuse and (b) alcohol or illicit drug dependence or abuse. Models for alcohol dependence and

illicit drug dependence are displayed in Table 6.12. Finally, models for marijuana dependence

and other illicit drug dependence are shown in Table 6.13.

With statistical adjustment for demographic characteristics, onset of marijuana use before

age 18 predicted increased odds of being classified with dependence on or abuse of either

alcohol or other illicit drugs among adult marijuana users who reported the use in the past year

(Table 6.11). Relative to an onset of marijuana use after age 20, an onset of use between the ages

of 18 and 20 was not significant in predicting recent substance dependence or abuse. Compared

with black marijuana users, white users were at decreased odds of meeting the criteria for illicit

drug dependence or abuse in the past year (OR = 0.5). Recent marijuana users with a high school

diploma had decreased odds of illicit drug dependence or abuse when compared with users who

attended college.

Among recent marijuana users, age at onset of marijuana use was not found to be

associated with alcohol dependence in the model (Table 6.12). In comparison, an onset of

marijuana use before age 21 was associated with an increased likelihood of being classified with

illicit drug dependence as compared with users with an onset at age 21 or older. Those with an

onset before age 15 were an estimated 8.3 times more likely than those with an onset after age 20

to be dependent on one or more illicit drugs. Those with an onset between the ages of 15 and 20

were about 3 times more likely than those with an onset after age 20 to be dependent on one or

more illicit drugs. As noted in the finding for illicit drug dependence or abuse, white recent

marijuana users were less likely than black users to be dependent on an illicit drug (OR = 0.4).

Finally, multiple logistic regression showed that, among adult recent marijuana users, 

early-onset of marijuana use increased the likelihood of being dependent on both marijuana and

other illicit drugs (Table 6.13). Relative to those with an onset of marijuana use after age 20,

those reporting an onset before age 15 had an estimated OR of 5.1 for marijuana dependence and

an OR of 17.0 for other illicit drug dependence. In addition, recent marijuana users aged 50 years

old or older and black users were more likely to be classified with dependence on other illicit

drugs than younger and white recent marijuana users.
71

Table 6.1 Percentages with Lifetime and Past Year Use of Heroin, Cocaine, and

Psychotherapeutics among Adults Aged 26 or Older, by Age at First Marijuana Use

and Age Groups: 1999 and 2000

Age in Years

Age of Marijuana

Initiation in Years

Heroin Cocaine Any Psychotherapeutic

Lifetime Past Year Lifetime Past Year Lifetime Past Year

Total 14 or younger 9.2 0.6 62.0 6.9 53.9 11.5

15-17 4.2 0.2 40.9 3.5 36.5 5.6

18-20 3.0 0.1 28.8 1.8 26.6 3.9

21 or older 1.1 0.2 16.4 0.8 20.6 2.9

Never used marijuana 0.1 0.0 0.6 0.1 5.1 1.2

26-34 14 or younger 5.1 0.1 57.5 8.9 48.6 12.3

15-17 2.3 0.3 34.5 4.5 29.8 7.0

18-20 1.2 0.1 19.4 2.4 19.4 5.1

21 or older 0.5 0.0 14.9 1.5 17.4 5.0

Never used marijuana 0.1 0.0 1.0 0.1 6.6 1.8

35-49 14 or younger 11.6 1.0 65.7 5.2 57.7 10.9

15-17 4.8 0.2 44.3 3.0 39.8 5.1

18-20 3.0 0.1 32.2 1.5 27.6 3.4

21 or older 0.8 0.5 20.2 1.4 20.5 3.3

Never used marijuana 0.1 0.0 1.2 0.1 6.2 6.2

50+ 17 or younger 13.4 0.0 37.4 6.0 38.5 4.1

18-20 5.8 0.2 29.6 2.0 33.2 4.0

21 or older 1.5 0.0 14.1 0.2 21.5 2.1

Never used marijuana 0.0 0.0 0.2 0.0 4.1 1.0

Note: Nonmedical use of any prescription-type psychotherapeutic indicates using pain relievers, tranquilizers, stimulants, or

sedatives at least once. Indicated use does not include over-the-counter drugs.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
72

Table 6.2 Percentages with Past Year Heavy Marijuana Use and Heavy Use of Other Illicit Drugs

among Adults Aged 26 or Older, by Age at First Marijuana Use and Age Groups:

1999 and 2000

Age in Years

Age of Marijuana

Initiation in Years Heavy Marijuana Use Heavy Use of Other Illicit Drugs

Total 14 or younger 5.0 6.3

15-17 1.2 2.8

18-20 0.6 1.4

21 or older 0.5 1.1

Never used marijuana 0.0 0.5

26-34 14 or younger 7.3 7.0

15-17 1.7 3.2

18-20 1.3 1.3

21 or older 0.5 1.8

Never used marijuana 0.0 0.6

35-49 14 or younger 3.5 5.5

15-17 1.0 2.6

18-20 0.4 1.6

21 or older 0.7 1.7

Never used marijuana 0.0 0.6

50+ 17 or younger 0.0 6.1

18-20 0.2 0.9

21 or older 0.4 0.5

Never used marijuana 0.0 0.4

Note: Heavy marijuana use refers to using marijuana on 300 or more days in the past year. Heavy use of other illicit drugs

refers to using cocaine, hallucinogens, inhalants, heroin, or any prescription-type psychotherapeutic used

nonmedically (i.e., pain relievers, sedatives, tranquilizers, or stimulants) on at least 50 days in the past year.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
73

Table 6.3 Percentages with Past Year Alcohol and/or Illicit Drug Dependence or Abuse among

Adults Aged 26 or Older, by Age at First Marijuana Use and Age Groups: 2000

Age in

Years

Age of Marijuana

Initiation in Years

Illicit Drug

Dependence

or Abuse

Alcohol or

Illicit Drug

Dependence

or Abuse

Alcohol

Dependence

Illicit Drug

Dependence

Marijuana

Dependence

Other Illicit

Drug

Dependence

Total 14 or younger 6.2 18.0 6.8 4.5 2.5 2.7

15-17 2.2 9.5 3.6 1.4 0.7 0.9

18-20 2.0 8.3 3.5 1.7 0.8 1.2

21 or older 1.3 7.6 3.2 0.7 0.2 0.5

Never used marijuana 0.2 2.1 0.9 0.1 0.0 0.1

26-34 14 or younger 7.7 19.2 6.7 5.7 3.3 3.2

15-17 2.9 13.1 4.1 1.7 0.8 1.1

18-20 1.8 11.4 4.3 1.3 0.9 0.5

21 or older 3.0 13.7 4.0 0.7 0.6 0.1

Never used marijuana 0.4 3.4 1.0 0.2 0.0 0.2

35-49 14 or younger 5.0 17.3 6.5 3.4 2.0 2.0

15-17 1.7 7.8 3.5 1.4 0.7 0.8

18-20 1.8 7.5 3.2 1.7 0.8 1.1

21 or older 1.7 8.0 3.8 1.2 0.0 1.2

Never used marijuana 0.2 2.6 1.4 0.1 0.0 0.1

50+ 17 or younger 8.2 9.8 4.6 3.6 0.0 3.6

18-20 2.8 7.2 3.4 2.1 0.4 2.1

21 or older 0.6 5.7 2.7 0.4 0.2 0.2

Never used marijuana 0.1 1.4 0.6 0.1 0.0 0.1

Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs:

marijuana/hashish, cocaine (including crack), heroin, hallucinogens (including LSD and PCP), inhalants, or any

prescription-type psychotherapeutic used nonmedically. Other illicit drug dependence indicates meeting the

dependence criteria of at least one of the following drugs: cocaine, hallucinogens, inhalants, heroin, pain relievers,

sedatives, tranquilizers, or stimulants. Dependence or abuse is based on the definition found in the 4th edition of the

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
74

Table 6.4 Adjusted Odds Ratios of Lifetime Use of Heroin, Cocaine, and Psychotherapeutics among Lifeti

26 or Older: 1999 and 2000

Variables

Lifetime Heroin Use Lifetime Cocaine Use 

Odds

Ratio

95% Confidence

Interval

Odds

Ratio

 95% Confidence

Interval

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 15.45 (7.56 - 31.55) 7.95 (6.53 - 9.68) 15-17 vs. 21 or older 6.10 (2.95 - 12.58) 3.27 (2.76 - 3.87) 18-20 vs. 21 or older 3.53 (1.73 - 7.20) 1.88 (1.57 - 2.25) 

Age in Years

26-34 vs. 50 or older 0.22 (0.13 - 0.38) 0.91 (0.73 - 1.12) 35-49 vs. 50 or older 0.53 (0.30 - 0.91) 1.41 (1.14 - 1.74) 

Gender

Male vs. female 1.61 (1.21 - 2.13) 1.33 (1.21 - 1.46) 

Race/Ethnicity

White vs. black 0.43 (0.29 - 0.64) 1.12 (0.93 - 1.34) Hispanic vs. black 0.65 (0.38 - 1.12) 1.14 (0.88 - 1.48) Other1 vs. black 0.52 (0.23 - 1.16) -- (-- - --) 

Asian/Pacific Islander/Native Hawaiian vs. black -- (-- - --) 0.60 (0.38 - 0.95) American Indian or Alaska Native vs. black -- (-- - --) 1.82 (1.13 - 2.93) More than one race vs. black -- (-- - --) 1.19 (0.67 - 2.10) 

Education

Less than high school vs. at least some college 1.44 (0.96 - 2.17) 1.04 (0.88 - 1.21) High school graduate vs. at least some college 1.03 (0.77 - 1.38) 0.90 (0.80 - 1.00) 

-- Not available.Note: Nonmedical use of any prescription-type psychotherapeutic indicates using pain relievers, tranquilizers, stimulants, or sedatives a

not include over-the-counter drugs.

1 Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
75

Table 6.5 Adjusted Odds Ratios of Past Year Use of Heroin, Cocaine, and Psychotherapeutics among Life

Aged 26 or Older: 1999 and 2000

Variables

Past Year Heroin Use Past Year Cocaine Use P

Odds

Ratio

95% Confidence

Interval

Odds

Ratio

95% Confidence

Interval

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 2.46 (0.54 - 11.28) 7.01 (3.60 - 13.66) 15-17 vs. 21 or older 0.91 (0.21 - 3.96) 3.81 (1.99 - 7.31) 18-20 vs. 21 or older 0.56 0.10 - 3.09) 2.04 (1.02 - 4.09) 

Age in Years

26-34 vs. 50 or older 2.12 (0.23 - 19.96) 1.87 (0.83 - 4.23) 35-49 vs. 50 or older 6.04 (0.71 - 51.38) 1.19 (0.51 - 2.78) 

Gender

Male vs. female 0.60 (0.26 - 1.41) 1.35 (1.03 - 1.76) 

Race/Ethnicity

White vs. black 0.55 (0.20 - 1.52) 0.54 (0.39 - 0.76) Hispanic vs. black -- (-- - --) 0.74 (0.43 - 1.29) Other1 vs. black 1.51 (0.40 - 5.78) -- (-- - --) 

Asian/Pacific Islander/Native Hawaiian vs. black -- (-- - --) 0.23 (0.07 - 0.76) American Indian or Alaska Native vs. black -- (-- - --) 1.56 (0.57 - 4.27) More than one race vs. black -- (-- - --) 0.81 (0.32 - 2.06) 

Education

Less than high school vs. at least some college 1.74 (0.60 - 5.03) 2.29 (1.54 - 3.40) High school graduate vs. at least some college 0.93 (0.36 - 2.35) 1.28 (1.00 - 1.64) 

-- Not available.Note: For past year heroin use, three racial/ethnic categories were used: white; black; and Hispanic, American Indian/Alaska Native, Asian/Pacific I

than one race. Black was used as the reference group. Nonmedical use of any prescription-type psychotherapeutic indicates using pain relieversedatives at least once. Indicated use does not include over-the-counter drugs.

1 Hispanic, Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
76

Table 6.6 Adjusted Odds Ratios of Past Year Heavy Marijuana Use and Heavy Use of Other Illicit Drugs a

Users Aged 26 or Older: 1999 and 2000

Variables

Heavy Marijuana Use Heavy 

Odds Ratio 95% Confidence Interval Odds Ratio 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 5.30 (2.43 - 11.56) 4.49 15-17 vs. 21 or older 1.36 (0.63 - 2.95) 2.12 18-20 vs. 21 or older 0.82 (0.32 - 2.13) 1.15 

Age in Years

26-34 vs. 50 or older 4.73 (1.33 - 16.83) 1.72 35-49 vs. 50 or older 2.31 (0.64 - 8.29) 1.52 

Gender

Male vs. female 2.12 (1.47 - 3.05) 1.11 

Race/Ethnicity

White vs. black 1.25 (0.77 - 2.02) 0.62 Hispanic vs. black 1.01 (0.53 - 1.95) 1.23 Other1 vs. black 1.17 (0.45 - 3.01) -- 

Asian/Pacific Islander/Native Hawaiian vs. black -- (-- - --) 0.54 

American Indian or Alaska Native vs. black -- (-- - --) 2.63 More than one race vs. black -- (-- - --) 0.77 

Education

Less than high school vs. at least some college 2.43 (1.47 - 3.99) 2.99 High school graduate vs. at least some college 2.74 (1.24 - 2.43) 1.57 

-- Not available.Note: For heavy marijuana use, four racial/ethnic categories were used: white; black; Hispanic; and American Indian/Alaska Native, Pacific Islander

race. Black was used as the reference group. Heavy marijuana use refers to using marijuana on 300 or more days in the past year. Heavy use o

cocaine, hallucinogens, inhalants, heroin, or any prescription-type psychotherapeutic used nonmedically (i.e., pain relievers, sedatives, tranqui

days in the past year.

1 Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
77

Table 6.7 Adjusted Odds Ratios of Past Year Illicit Drug Dependence or Abuse and Alcohol or Illicit Drug 

among Lifetime Marijuana Users Aged 26 or Older: 2000

Variables

Illicit Drug Dependence or Abuse Alcohol or I

Odds Ratio 95% Confidence Interval Odds Ratio 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 4.74 (1.86 - 12.08) 1.90 15-17 vs. 21 or older 1.74 (0.69 - 4.36) 0.99 18-20 vs. 21 or older 1.51 (0.61 - 3.72) 0.94 

Age in Years

26-34 vs. 50 or older 1.31 (0.44 - 3.95) 2.20 35-49 vs. 50 or older 0.88 (0.31 - 2.52) 1.43 

Gender

Male vs. female 1.12 (0.72 - 1.74) 1.94 

Race/Ethnicity

White vs. black 0.52 (0.30 - 0.88) 0.93 Hispanic vs. black 0.89 (0.45 - 1.75) 0.95 Asian/Pacific Islander/Native Hawaiian vs. black 0.13 (0.03 - 0.63) 0.79 American Indian or Alaska Native vs. black 0.96 (0.26 - 3.46) 1.36 More than one race vs. black 3.01 (0.85 - 10.74) 1.59 

Education

Less than high school vs. at least some college 1.81 (1.05 - 3.13) 1.91 High school graduate vs. at least some college 0.75 (0.51 - 1.10) 1.32 

Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs: marijuana/hashish, coca

hallucinogens (including LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Dependence o

found in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
78

Table 6.8 Adjusted Odds Ratios of Past Year Alcohol Dependence and Illicit Drug Dependence among Lif

Aged 26 or Older: 2000

Variables

Alcohol Dependence Il

Odds Ratio 95% Confidence Interval Odds Ratio 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 1.64 (0.91 - 2.95) 6.19 15-17 vs. 21 or older 0.97 (0.57 - 1.65) 1.98 18-20 vs. 21 or older 1.02 (0.56 - 1.84) 2.29 

Age in Years

26-34 vs. 50 or older 1.51 (0.75 - 3.03) 1.20 35-49 vs. 50 or older 1.33 (0.67 - 2.64) 0.99 

Gender

Male vs. female 1.72 (1.23 - 2.41) 1.00 

Race/Ethnicity

White vs. black 0.83 (0.50 - 1.36) 0.49 Hispanic vs. black 0.67 (0.34 - 1.33) 0.57 Asian/Pacific Islander/Native Hawaiian vs. black 1.15 (0.23 - 5.64) 0.17 American Indian/Alaska Native vs. black 0.96 (0.23 - 3.99) 0.27 More than one race 0.81 (0.24 - 2.77) 1.09 

Education

Less than high school vs. at least some college 3.34 (2.21 - 5.07) 1.81 High school graduate vs. at least some college 1.62 (1.15 - 2.30) 0.69 

Note: Illicit drug dependence indicates dependence on at least one of the following drugs: marijuana/hashish, cocaine (including crack)

LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Dependence is based on the definition 

Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
79

Table 6.9 Adjusted Odds Ratios of Past Year Marijuana Dependence and Other Illicit Drug Dependence a

Users Aged 26 or Older: 2000

Variables

Marijuana Dependence Othe

Odds Ratio 95% Confidence Interval Odds Ratio 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 9.77 (2.82 - 33.89) 5.67 15-17 vs. 21 or older 2.67 (0.76 - 9.38) 1.94 18-20 vs. 21 or older 2.98 (0.79 - 11.25) 2.52 

Age in Years

26-34 vs. 50 or older 2.47 (0.69 - 8.83) 0.76 35-49 vs. 50 or older 1.70 (0.46 - 6.27) 0.80 

Gender

Male vs. female 1.31 (0.71 - 2.40) 0.83 

Race/Ethnicity

White vs. black 0.52 (0.21 - 1.31) 0.53 Hispanic vs. black -- (-- - --) 0.80 Other1 vs. black 0.47 (0.12 - 1.77) -- 

Other2 vs. black -- (-- - --) 0.70 

Education

Less than high school vs. at least some college 0.95 (0.41 - 2.24) 2.98 High school graduate vs. at least some college 0.46 (0.23 - 0.92) 1.05 

-- Not available.Note: For marijuana dependence, three racial/ethnic categories were used: white; black; and Hispanic, American Indian/Alaska Native, 

Hawaiian, and more than one race. Black was used as the reference group. Other illicit drug dependence indicates meeting the deof the following drugs: cocaine, hallucinogens, inhalants, heroin, pain relievers, sedatives, tranquilizers, or stimulants. Dependenin the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

1 Hispanic, Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.2 Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
80

Table 6.10 Percentages with Past Year Alcohol and/or Illicit Drug Dependence or Abuse among Past Year 

Aged 26 or Older, by Age at First Marijuana Use: 2000

Age of MarijuanaInitiation in Years

Illicit Drug

Dependence or

Abuse 

Alcohol or Illicit

Drug Dependence

or Abuse

Alcohol

Dependence

Illicit Drug

Dependence

Marijuana

Dependence

14 or younger 20.7 39.5 11.7 15.2 8.8 15-17 12.6 27.8 9.4 8.0 4.7 18-20 9.7 22.9 11.0 7.9 7.1 21 or older 7.5 16.7 5.4 3.4 2.1 Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs: marijuana/hashish, coca

heroin, hallucinogens (including LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Other 

indicates meeting the dependence criteria of one or more of the following drugs: cocaine, hallucinogens, inhalants, heroin, pain rtranquilizers, or stimulants. Dependence or abuse is based on the definition found in the 4th edition of the Diagnostic and Statistic

Disorders (DSM-IV).

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
81

Table 6.11 Adjusted Odds Ratios of Illicit Drug Dependence or Abuse and Alcohol or Illicit Drug Depende

Lifetime Marijuana Users Aged 26 or Older Who Also Used Marijuana in the Past Year: 2000

Illicit Drug Dependence or Abuse Alcohol or Illicit Drug 

Variables Odds Ratio 95% Confidence Interval Odds Ratio 95% 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 5.69 (2.12 - 15.28) 3.63 15-17 vs. 21 or older 2.94 (1.03 - 8.36) 2.17 18-20 vs. 21 or older 1.80 (0.71 - 4.59) 1.63 

Age in Years

26-34 vs. 50 or older 0.38 (0.13 - 1.09) 0.80 35-49 vs. 50 or older 0.37 (0.14 - 1.01) 0.76 

Gender

Male vs. female 0.89 (0.57 - 1.39) 1.16 

Race/Ethnicity

White vs. black 0.46 (0.26 - 0.80) 1.01 Hispanic vs. black 1.37 (0.59 - 3.19) 1.31 Other1 vs. black 1.13 (0.49 - 2.62) -- 

Asian/Pacific Islander/Native Hawaiian vs.

black -- (-- - --) 0.23 

American Indian/Alaska Native vs. black -- (-- - --) 1.24 More than one race vs. black -- (-- - --) 1.68 

Education

Less than high school vs. at least some college 1.02 (0.62 - 1.68) 1.44 High school graduate vs. at least some college 0.62 (0.40 - 0.98) 0.92 

-- Not available.Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs: marijuana/hashish, coca

heroin, hallucinogens (including LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Depen

on the definition found in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

1 Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
82

Table 6.12 Adjusted Odds Ratios of Past Year Alcohol Dependence and Illicit Drug Dependence among Li

Users Aged 26 or Older Who Also Used Marijuana in the Past Year: 2000

Alcohol Dependence Illicit Drug 

Variables Odds Ratio 95% Confidence Interval Odds Ratio 95% 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 2.45 (0.79 - 7.63) 8.33 15-17 vs. 21 or older 2.09 (0.69 - 6.32) 3.68 18-20 vs. 21 or older 2.56 (0.94 - 6.95) 3.16 

Age in Years

26-34 vs. 50 or older 0.77 (0.17 - 3.49) 0.41 35-49 vs. 50 or older 0.86 (0.19 - 3.84) 0.45 

Gender

Male vs. female 1.16 (0.69 - 1.95) 0.81 

Race/Ethnicity

White vs. black 1.45 (0.58 - 3.62) 0.41 Hispanic vs. black 1.61 (0.56 - 4.65) 0.68 Other1 vs. black 1.09 (0.22 - 5.33) 0.41 

Education

Less than high school vs. at least some college 2.94 (1.55 - 5.59) 0.90 High school graduate vs. at least some college 1.35 (0.76 - 2.41) 0.56 

Note: Illicit drug dependence indicates dependence on at least one of the following: marijuana/hashish, cocaine (including crack), hero

(including LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Dependence is based on the 

edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

1 Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
83

Table 6.13 Adjusted Odds Ratios of Past Year Marijuana Dependence and Other Illicit Drug Dependence a

Marijuana Users Aged 26 or Older Who Also Used Marijuana in the Past Year: 2000

Marijuana Dependence Other Illicit Dr

Variables Odds Ratio 95% Confidence Interval Odds Ratio 95% 

Age at First Marijuana Use in Years

14 or younger vs. 21 or older 5.05 (1.49 - 17.15) 17.03 15-17 vs. 21 or older 2.27 (0.63 - 8.15) 7.73 18-20 vs. 21 or older 3.55 (0.90 - 14.03) 3.97 

Age in Years

26-34 vs. 50 or older 1.05 (0.27 - 4.11) 0.19 35-49 vs. 50 or older 1.08 (0.26 - 4.53) 0.25 

Gender

Male vs. female 0.84 (0.45 - 1.57) 0.82 

Race/Ethnicity

White vs. black 0.62 (0.25 - 1.50) 0.38 Other1 vs. black 0.58 (0.16 - 2.16) 0.83 

Education

Less than high school vs. at least some college 0.75 (0.33 - 1.72) 1.69 High school graduate vs. at least some college 0.42 (0.20 - 0.85) 0.99 

Note: Other illicit drug dependence indicates meeting the dependence criteria of one or more of the following drugs: cocaine, hallucino

pain relievers, sedatives, tranquilizers, or stimulants. Dependence is based on the definition found in the 4th edition of the Diagno

Manual of Mental Disorders (DSM-IV).

1 Hispanic, Asian/Pacific Islander/Native Hawaiian, American Indian/Alaska Native, and more than one race.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
84
85

7. Discussion

Marijuana has continued to be the most commonly used illicit drug among both youths

and adults. The rate of marijuana initiation increased during the late 1960s and early 1970s, with

a peak in 1976 and 1977 (21.0 per 1,000 potential new users). After that period, the rate of new

marijuana users decreased to 8.5 in 1990, followed by an increase to 16.8 in 1996, then a

decrease to 13.6 in 1999. Aggregated 1999 and 2000 data indicate that there were approximately

2.5 million new marijuana users annually in 1997-1998 and 2.0 million new users in 1999.

Although the number of new users had decreased in 1999, it was still above the levels for 1989

and 1990 (1.4 million each year).

Incidence rates of marijuana use were generally higher among males than among

females. Among males, the highest peak was noted in 1976 and 1977 (close to 24.0). Since the

early 1980s, incidence rates declined, and the most recent peak for males was in 1997 (19.3).

Similar to the pattern of males, the incidence rate for females was lower during the 1980s. The

most recent peak for females was in 1996 (15.5). For both genders, the rate in 1999 was lower

than the rates from 1996 to 1998. The estimated mean age at first marijuana use was slightly

younger among males than females, but the trend suggested an increasing similarity for both

genders in some recent years. The mean age of first marijuana use remained at 17 years during

most of the 1990s.

Recent initiates were much more likely to be among youths and young adults than among

adults aged 21 or older. The annual age- and gender-specific incidence rate per 1,000 potential

users was highest among youths aged 15 to 17. Young adults aged 18 to 20 had slightly higher

incidence rates than youths aged 12 to 14, while adults aged 21 or older had a very low rate of

new use. Recently, American Indians/Alaska Natives appeared to have particularly high rates of

new users and younger age of first use than members of other racial/ethnic groups.

Recent initiation of marijuana use also varied by States and age groups. Colorado,

Delaware, Massachusetts, New Hampshire, and Vermont were ranked in the category with the

highest incidence rate for the overall, youth, and young adult groups. New Mexico had the

highest rate for the overall and youth groups. Minnesota was in the highest category for the

overall and young adult groups. By comparison, Louisiana had the lowest rate of recent new

users for the overall, youth, and young adult groups. In addition, Texas and Utah had the lowest

rate of recent initiation among youths and young adults.

Marijuana initiation varied somewhat by month of year. Overall, the annual average

number of marijuana initiates per day was 6,186 (3,197 and 2,989, respectively, for males and

females). Among males, the highest number of first marijuana users per day was noted in June
86

and July (around 4,300 initiates per day). Among females, increased rates of initiates were in

January (3,519 initiates per day) and July (3,625 initiates per day). Of all recent initiates who

started using marijuana before age 18, June (11.6 percent of all recent initiates) and July (12.0

percent) also had the most new users, while adult-onset marijuana users tended to have initiated

the use in January (10.9 percent), December (9.2 percent), or July (9.1 percent).

Any prior use of alcohol and/or cigarettes was strongly related to the onset of recent

marijuana initiation, regardless of the age when alcohol or cigarettes were first used. Of all

recent marijuana initiates, 60 percent used both alcohol and cigarettes before starting their

marijuana use. Fewer than 10 percent had never used alcohol and cigarettes at the time of

marijuana initiation, and the remaining recent initiates had used either alcohol only (16.6

percent) or cigarettes only (14.8 percent) prior to their first marijuana use.

Multiple logistic regression of persons aged 12 to 25 found that younger persons under

age 21, males, blacks, American Indians/Alaska Natives, and persons living in the West or

metropolitan areas were likely to become new marijuana users recently. For some young adults

aged 18 to 25, the assumption of adult roles (e.g., becoming married) may protect them from

marijuana initiation. Multiple logistic regression also confirmed that the risk of recent marijuana

initiation increased with increasing age among youths aged 12 to 14, but the risk decreased with

increasing age among those aged 15 to 25.

Logistic regression models, holding constant demographic characteristics, revealed that

earlier age at first use of marijuana, particularly an onset before age 15, predicted increased odds

for the following: (a) heavy use of marijuana and other illicit drugs, (b) dependence on or abuse

of alcohol and/or other illicit drugs, and (c) dependence on marijuana or other illicit drugs in the

past year.

These national estimates on incidence and trend data provide useful information for

planning and delivering substance abuse services, as well as baseline data for further

investigations. The strength of the association between alcohol and cigarette use with later

marijuana initiation suggests that reducing the onset of alcohol or cigarette use may have some

positive influences on the prevention of marijuana initiation. Some new marijuana users,

particularly early-onset users, may have a significant impact on the future demand for substance

abuse treatment because of their increased odds of progressing into heavier drug involvement

and probably other drug-related health risk behaviors. Substance abuse service needs for young

marijuana users warrant further study because recent data reveal a younger population of drug

users seeking treatment for marijuana abuse (OAS, 2001c). Early identification of subgroups

vulnerable to heavier substance use and increasing their access to substance abuse services may

prevent them from more serious substance use involvement and decrease subsequent societal

costs related to substance use or abuse. These national estimates reveal emerging trends of new
87

marijuana use by some subgroups that could be targeted for prevention (e.g., blacks and

American Indians/Alaska Natives).

The pathways to illicit drug use and/or dependence involve multiple factors and

processes. To better inform policy for substance use prevention, further research should focus on

(a) identifying the processes that account for subgroup variations in illicit drug use and/or

dependence and (b) understanding the factors that explain the developmental sequence of

substance use involvement, including determinants of early initial use of marijuana or other

substances.

In conclusion, the data indicate a decreased rate of new marijuana use in 1999. Youths

aged 15 to 17 had the highest rate of becoming new marijuana users in recent years. Whites were

less likely than blacks to start to use marijuana recently, and young American Indians/Alaska

Natives appeared to have an elevated risk of becoming new marijuana users in recent years.

Further analysis of these and future NHSDA data will help to confirm the findings from the 1999

and 2000 surveys and to track changes in the trend of new marijuana use by at-risk subgroups.
88
89

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95

Appendix A: Statistical Methods and

Limitations of the Data
96
97

Appendix A: Statistical Methods and

Limitations of the Data

A.1 Target Population

An important limitation of the National Household Survey on Drug Abuse (NHSDA)

estimates of drug use prevalence is that they are only designed to describe the target population

of the survey—the civilian, noninstitutionalized population aged 12 or older. Although this

population includes almost 98 percent of the total U.S. population aged 12 or older, it excludes

some important and unique subpopulations who may have very different drug-using patterns. For

example, the survey excludes active military personnel, who have been shown to have

significantly lower rates of illicit drug use. Persons living in institutional group quarters, such as

prisons and residential drug treatment centers, are not included in the NHSDA and have been

shown in other surveys to have higher rates of illicit drug use. Also excluded are homeless

persons not living in a shelter on the survey date, another population shown to have higher than

average rates of illicit drug use.

A.2 Sampling Error and Statistical Significance

The sampling error of an estimate is the error caused by the selection of a sample instead

of conducting a census of the population. Sampling error is reduced by selecting a large sample

and by using efficient sample design and estimation strategies, such as stratification, optimal

allocation, and ratio estimation.

With the use of probability sampling methods in the NHSDA, it is possible to develop

estimates of sampling error from the survey data. These estimates have been calculated for all

estimates presented in this report using a Taylor series linearization approach that takes into

account the effects of the complex NHSDA design features. The sampling errors are used to

identify unreliable estimates and to test for the statistical significance of differences between

estimates.

A.2.1 Variance Estimation for Totals

Estimates of proportions, such as drug use prevalence rates, take the form of nonlinear

statistics where the variances cannot be expressed in closed form. Variance estimation for

nonlinear statistics is performed using a first-order Taylor series approximation in the SUrvey

DAta ANalysis (SUDAAN) statistical software package developed by RTI (Shah et al., 1996).

The approximation is unbiased for sufficiently large samples and has proven to be at least as
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accurate and less costly to implement than its competitors, such as balanced repeated replication

or jackknife methods (Rao & Wu, 1985).

Corresponding to proportion estimates, , the number of drug users, , can be

estimated as

where is the estimated population total for domain d, and is the estimated proportion for

domain d. The standard error (SE) for the total estimate is obtained by multiplying the SE of the

proportion by , that is,

 .

This approach is theoretically correct when the domain size estimates are among those forced

to Census Bureau population projections through the weight calibration process. In these cases, 

 is clearly not subject to sampling error.

For domain totals where is not fixed, this formulation may still provide a good

approximation if we can reasonably assume that the sampling variation in is negligible

relative to the sampling variation in . In most analyses conducted for prior years, this has been

a reasonable assumption. SUDAAN also provides an option to directly estimate the variance of

the linear statistic that estimates a population total. Using this option did not affect the SE

estimates for the corresponding proportions presented in the same sets of tables.

A.2.2 Suppression Criteria for Unreliable Estimates

As has been done in past NHSDA reports, direct survey estimates considered to be

unreliable due to unacceptably large sampling errors are not shown in this report and are noted

by asterisks (*) in the tables containing such estimates found in the appendices. The criterion

used for suppressing all direct survey estimates was based on the relative standard error (RSE),

which is defined as the ratio of the standard error (SE) over the estimate. 

Proportion estimates (p) within the range [0<p<1], rates, and corresponding estimated

number of users were suppressed if

RSE[-ln(p)] > 0.175 when p < 0.5

or

RSE[-ln(1 - p)] > 0.175 when p $ 0.5 .
99

Using a first-order Taylor series approximation to estimate RSE[-ln(p)] and RSE[-ln(1 -

p)], we have the following, which was used for computational purposes:

[SE(p)/p ÷ -1n( p)] > 0.175 when p < 0.5

or

[SE(p)/(1-p) ÷ -1n(1 - p)] > 0.175 when p $ 0.5 .

The separate formulas for p < 0.5 and p $ 0.5 produce a symmetric suppression rule; that

is, if p is suppressed, then so will 1 - p. This is an ad hoc rule that requires an effective sample

size in excess of 50. When 0.05 < p < 0.95, the symmetric properties of the rule produces a local

maximum effective sample size of 68 at p = 0.5. Thus, estimates with these values of p along

with effective sample sizes falling below 68 are suppressed. A local minimum effective sample

size of 50 occurs at p = 0.2 and again at p = 0.8 within this same interval; so, estimates are

suppressed for values of p with effective sample sizes below 50. 

In NHSDAs prior to the 2000 NHSDA, these varying sample size restrictions sometimes

produced unusual occurrences of suppression for a particular combination of prevalence rates.

For example, in some cases, lifetime prevalence rates near p = 0.5 were suppressed (effective

sample size was <68 but >50), while not suppressing the corresponding past year or past month

estimates near p = 0.2 (effective sample sizes were >50). To reduce the occurrence of this type of

inconsistency, a minimum effective sample size of 68 was added to the suppression criteria. As p

approached 0.00 or 1.00 outside the interval (0.05, 0.95), the suppression criteria still required

increasingly larger effective sample sizes. For example, if p = 0.01 and 0.001, the effective

sample size must exceed 152 and 684, respectively.

Also new to the 2000 survey were minimum nominal sample size suppression criteria (n

= 100) that protect against unreliable estimates caused by small design effects and small nominal

sample sizes. Prevalence estimates were also suppressed if they were close to 0 or 100 percent

(i.e., if p < 0.00005 or if p $ 0.99995). Estimates of other totals (e.g., number of initiates) along

with means and rates (both not bounded between 0 and 1) were suppressed if RSE(p) > 0.5.

Additionally, estimates of the mean age at first use were suppressed if the sample size was

smaller than 10 respondents; moreover, the estimated incidence rate and number of initiates were

suppressed if they rounded to 0. The suppression criteria for various NHSDA estimates are

summarized in Table A.1.

A.3 Nonsampling Error

Nonsampling errors can occur from nonresponse, coding errors, computer processing

errors, errors in the sampling frame, reporting errors, and other errors not due to sampling.

Nonsampling errors are reduced through data editing, statistical adjustments for nonresponse,
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close monitoring and periodic retraining of interviewers, and improvement in various quality

control procedures.

Although nonsampling errors can often be much larger than sampling errors,

measurement of most nonsampling errors is difficult or impossible. However, some indication of

the effects of some types of nonsampling errors can be obtained through proxy measures, such as

response rates and from other research studies.

A.3.1 Screening and Interview Response Rate Patterns

Response rates for the NHSDA were stable for the period from 1994 to 1998, with the

screening response rate at about 93 percent and the interview response rate at about 78 percent

(response rates discussed in this appendix are weighted). In 1999, the computer-assisted

interviewing (CAI) screening response rate was 89.6 percent and the interview response rate was

68.6 percent. A more stable and experienced field interviewer (FI) workforce improved these

rates in 2000. Of the 182,576 eligible households sampled for the 2000 NHSDA main study,

169,769 were successfully screened, for a weighted screening response rate of 92.8 percent

(Table A.2). In these screened households, a total of 91,961 sample persons were selected, and

completed interviews were obtained from 71,764 of these sample persons, for a weighted

interview response rate of 73.9 percent (Table A.3). A total of 10,109 (15.0 percent) sample

persons were classified as refusals, 4,834 (5.5 percent) were not available or never at home, and

5,254 (5.5 percent) did not participate for various other reasons, such as physical or mental

incompetence or language barrier. Tables A.4 and A.5 show the distribution of the selected

sample by interview code and age group. The weighted interview response rate was highest

among 12 to 17 year olds (82.6 percent), females (75.1 percent), blacks and Hispanics (76.2 and

78.0 percent, respectively), in nonmetropolitan areas (77.6 percent), and among persons residing

in the South (76.4 percent) (Table A.6). 

The increase in nonresponse between the 1998 and 1999 NHSDAs can be attributed

primarily to the hiring of many new and inexperienced FIs in 1999 and a larger than usual

turnover. By the end of 2000, the interviewer workforce primarily consisted of experienced

interviewers, with fewer FIs leaving for other jobs. In 1999, there were 1,997 FIs hired and

trained to conduct the CAI and paper-and-pencil interviewing (PAPI) surveys. More than a third

of them did not complete the survey year (37.7 percent). In 2000, the number of trained

interviewers decreased to 1,356 (because only CAI interviews were conducted in 2000), and the

attrition rate dropped to 29.8 percent. Both prior NHSDA experience and on-the-job experience

were shown to be related to nonresponse. Previously experienced interviewers and interviewers

with one, two, or three quarters of on-the-job experience were more successful at obtaining an

interview.
101

The overall weighted response rate, defined as the product of the weighted screening

response rate and weighted interview response rate, was 61.5 percent in 1999 and 68.6 percent in

2000 (an 11.5 percent improvement over the 1999 rate). Nonresponse bias can be expressed as

the product of the response rate (R) and the difference between the characteristic of interest

between respondents and nonrespondents in the population (Pr - Pnr). Thus, assuming the

quantity (Pr - Pnr) is fixed over time, the improvement in response rates in 2000 should result in

estimates with lower nonresponse bias.

A.3.2 Inconsistent Responses and Item Nonresponse

Among survey participants, item response rates were above 98 percent for most

questionnaire items. However, inconsistent responses for some items, including the drug use

items, were common. Estimates of substance use from the NHSDA are based on the responses to

multiple questions by respondents, so that the maximum amount of information is used in

determining whether a respondent is classified as a drug user. Inconsistencies in responses are

resolved through a logical editing process that involves some judgment on the part of survey

analysts and is a potential source of nonsampling error. Because of the automatic routing through

the CAI questionnaire (e.g., lifetime drug use questions that skip entire modules when answered

"no"), there is less editing of this type than in the PAPI questionnaire used in previous years.

In addition, less logical editing is used because with the CAI data, statistical imputation

is relied upon more heavily to determine the final values of drug use variables in cases where

there is the potential to use logical editing to make a determination. The combined amount of

editing and imputation in the CAI data is still considerably less than the total amount used in

prior PAPI surveys. For the 2000 CAI data, for example, 3.2 percent of the estimate of past

month hallucinogen use is based on logically edited cases and 5.4 percent on imputed cases, for

a combined amount of 8.6 percent. For the 1999 CAI data, 1.7 percent of the estimate of past

month hallucinogen use is based on logically edited cases and 4.6 percent on imputed cases, for

a combined amount of 6.2 percent. In the 1998 NHSDA (administered using PAPI), the amount

of editing and imputation for past month hallucinogen use was 60 and 0 percent, respectively, for

a total of 60 percent. The combined amount of editing and imputation for the estimate of past

month heroin use is 5.0 percent for the 2000 CAI, 14.8 percent for the 1999 CAI, and 37.0

percent for the 1998 PAPI data.

A.3.3 Validity of Self-Reported Use

NHSDA estimates are based on self-reports of drug use, and their value depends on

respondents' truthfulness and memory. Although many studies have generally established the

validity of self-report data and the NHSDA procedures were designed to encourage honesty and

recall, some degree of underreporting is assumed (Harrell, 1997; Harrison & Hughes, 1997;
102

Rouse, Kozel, & Richards, 1985). No adjustment to NHSDA data is made to correct for this. The

methodology used in the NHSDA has been shown to produce more valid results than other selfreport methods (e.g., by telephone) (Aquilino, 1994; Turner, Lessler, & Gfroerer, 1992).

However, comparisons of NHSDA data with data from surveys conducted in classrooms suggest

that underreporting of drug use by youths in their homes may be substantial (Gfroerer, 1993;

Gfroerer et al., 1997).

A.4 Incidence Estimates

For diseases, the incidence rate for a population is defined as the number of new cases of

the disease, N, divided by the person time, PT, of exposure or:

.

The person time of exposure can be measured for the full period of the study or for a shorter

period. The person time of exposure ends at the time of diagnosis (e.g., Greenberg, Daniels,

Flanders, Eley, & Boring, 1996, pp. 16-19). Similar conventions are applied for defining the

incidence of first use of a substance.

Beginning in 1999, the NHSDA questionnaire allows for collection of year and month of

first use for recent initiates. Month, day, and year of birth are also obtained directly or imputed

in the process. In addition, the questionnaire call record provides the date of the interview. By

imputing a day of first use within the year and month of first use reported or imputed, the key

respondent inputs in terms of exact dates are known. Exposure time can be determined in terms

of days and converted to an annual basis.

Having exact dates of birth and first use also allows us to determine person time of

exposure during the targeted period, t. Let the target time period for measuring incidence be

specified in terms of dates; for example, for the period 1998 we would specify:

,

a period that includes 1 January 1998 and all days up to but not including 1 January 1999. The

target age group can also be defined by a half-open interval as . For example, the

age group 12 to 17 would be defined by for persons at least age 12, but not yet age

18. If person I was in age group a during period t, the time and age interval, ,can then be

determined by the intersection:
103

assuming we can write the time of birth as in terms of day ( ), month ( ), and year

( ). Either this intersection will be empty ( ) or we will designate it by the halfopen interval where:

and

.

The date of first use, , is also expressed as an exact date. An incident of first drug d use by

person I in age group a occurs in time t if . The indicator function 

used to count incidents of first use is set to 1 when , and to 0 otherwise. The

person time exposure measured in years and denoted by for a person I of age group a

depends on the date of first use. If the date of first use precedes the target period ( ),

then . If the date of first use occurs after the target period or if person I has never

used drug d, then

 .

If the date for first use occurs during the target period , then

 .

Note that both and are set to zero if the target period is empty; that is,

person I is not in age group a during time t. The incidence rate is then estimated as a weighted

ratio estimate:

where the are the analytic weights.

Prior to the 1999 survey, exact date data were not available for computing incidence

rates. For these rates, a person was considered to be of age a during the entire time interval t if

his or her ath birthday occurred during time interval t (generally, a single year). If the person

initiated use during the year, the person time exposure was approximated as one-half year for all

such persons rather than computing it exactly for each person.

Because of the new methodology, incidence estimates discussed in this report are not

strictly comparable with the estimates presented before the 1999 NHSDA. Because they are
104

based on retrospective reports by survey respondents, as was the case for earlier estimates, they

may be subject to some of the same kinds of biases.

Bias due to differential mortality occurs because some persons who were alive and

exposed to the risk of first drug use in the historical periods shown in the tables died before the

1999 NHSDA was conducted. This bias is probably very small for estimates shown in this

report. Incidence estimates are also affected by memory errors, including recall decay (tendency

to forget events occurring long ago) and forward telescoping (tendency to report that an event

occurred more recently than it actually did). These memory errors would both tend to result in

estimates for earlier years (i.e., 1960s and 1970s) that are downwardly biased (because of recall

decay) and estimates for later years that are upwardly biased (because of telescoping). There is

also likely to be some underreporting bias due to social acceptability of drug use behaviors and

respondents' fear of disclosure. This is likely to have the greatest impact on recent estimates,

which reflect more recent use and reporting by younger respondents. Finally, for drug use that is

frequently initiated at age 10 or younger, estimates based on retrospective reports 1 year later

underestimate total incidence because 11-year-old children are not sampled by the NHSDA.

Prior analyses showed that alcohol and cigarette (any use) incidence estimates could be

significantly affected by this.

Johnson et al. (1998) concluded that the marijuana incidence trend from the NHSDA was

biased because the reporting of initiation declines as the length of time between initiation and the

survey increases. However, their study did not address very recent estimates (i.e., 1996 to 1998),

which could be biased because they reflect recent drug use and because they are heavily based

on the reports of adolescents. To better understand the size of the biases and to assess the

reliability of estimates for recent years, OAS performed an analysis of estimates based on single

years of NHSDA data. This analysis focused on three drugs: cocaine, heroin, and marijuana.

Using the survey data from 1994 to 1998, estimates were made of the number of initiates, the

rate of initiation for youths aged 12 to 17, and the rate of initiation for persons aged 18 to 25. For

the 1994 survey, an estimate was made for the year 1993. For the 1995 survey, another estimate

was made for the year 1993. In this way, two recent estimates of the same year could be

compared. Similarly, the 1995 and 1996 data provided two estimates for 1994, the 1996 and

1997 surveys provided two estimates for 1995, and the 1997 and 1998 surveys provided two

estimates for 1996. Because these calculations represent two measurements of the same

population characteristic, they would ideally be the same. Examples of these estimates are shown

in Table A.7.

Drug initiation rates for youths aged 12 to 17 for the more hard-core drugs (e.g., cocaine

and heroin) appeared to be most prone to bias. For example, on average across the 4 survey

years, the estimate for the rate of initiation of cocaine use among youths aged 12 to 17 was 48

percent higher the first time the estimate could be made than the second time. This indicates a
105

probable bias in the estimation; however, it is unclear which estimate is the correct one. As a

result, one should be cautious in interpreting any changes between the prior year and the most

recent year in the initiation rates for youths of the more stigmatized drugs. Because only 5 years

of data were used to estimate how the rate of incidence changed between the first year it could

be estimated and the second, one should be cautious about inferring the magnitude of the bias

(e.g., that it was 48 percent for cocaine).

In Table A.7, the average ratio of 1-year recall to 2-year recall is calculated across 4

"years." Implicit in the table is the fact that the estimates for each ratio vary around the average.

For example, taking the 18 to 25 marijuana incidence numbers, the four individual ratios can be

calculated as 1.13, .75, 0.89, and 1.06. Although the average ratio was 0.96, the year-to-year

variation was much larger, ranging from 0.75 to 1.13. So, it is clear that for any single year, the

bias implied by the sample estimates could be negative or positive. Because we are not clear

whether the 1-year recall or the 2-year recall estimate is closer to an unbiased true value, the

estimate that we use for the most recent year could be as much as 25 percent too high or too low

in this example. The samples for 1999 and 2000 based on the new CAI method were

significantly larger than those in prior years; therefore, estimates of bias should suffer from less

sampling variability and the estimates should be less variable than before. Nevertheless, because

there are only 2 years under the new CAI method, and, therefore, only one calculation possible

of the ratio of the 1- to 2-year recall, more analysis is needed to see how stable the new estimates

from CAI will be.

A.5 Changes in NHSDA Measures of Substance Use Initiation

The redesign of the NHSDA in 1999 introduced some changes in the initiation of use

questions and the method of administration. In the presence of these changes, the overall data

processing and estimation methodologies were revised. A new incidence rate methodology was

developed. This section discusses the impact of methodological change on substance use

initiation measures: the change in the incidence rate estimation method and its impact, the

impact of the editing and imputing changes, and the questionnaire wording and administration

mode effects.

A.5.1 Impact of Imputation and Incidence Rate Calculation Method

Prior to 1999, the only questions about initiation of drug use asked the respondent to

report his or her age at first use for specified drugs. Each respondent's year at first use was

imputed based on the reported age at first use, the interview date, and the respondent's date of

birth. The imputed year was used to develop estimates of annual initiates and to develop the

respondent-level numerator and denominator inputs to the incidence rate calculation.
106

For the redesigned CAI instrument, additional questions about initiation of drug use were

included. Recent users (persons who first used at their current age or at their current age minus 1

year) were asked to report not only their age at first use for specified drugs, but also the month

and year of that first use. As a result, the exact month of first use for specified drugs was known

completely or in part (sometimes month or year were not reported) for 7 to 16 percent of the

drug users (depending on the drug) in the 1999 NHSDA sample. The questionnaire also changed

due to the routing logic used in the CAI instrument, which helped automatically resolve data

inconsistencies between related items. For example, respondents were asked their age at first

substance use and were prompted to review their response if the reported age at first use was

inconsistent with their reported current age.

These changes led to three methodology changes used in the calculation of the 1999

NHSDA drug incidence rates. First, missing age at first use data were imputed, which resulted in

consistent and nonmissing age at first use data for all users. Prior to the 1999 data, respondents

with a missing age at first use were simply excluded from the calculation of incidence numbers

and rates. Second, the assignment of the date of first use was refined such that the assigned date

was now consistent with other reported related information, such as drug use recency and

frequency data. Third, the improved data on age at first drug use and date of first drug use allow

a more exact person time of exposure during the targeted period to be determined. For example,

if a respondent was deemed a drug user and did not answer the age at first use question, the

response was statistically imputed to eliminate missing data. An exact date of first use (i.e., the

month, day, and year of first use) was then assigned by randomly picking a date within the 365

days corresponding to the respondent's age at first drug use. By using this date of first use in

conjunction with the birth date, the computation of the period of exposure can be determined

exactly in terms of whole days.

The new combined editing and imputation procedures flag more inconsistencies, impute

for both missing and inconsistent reports, and retain the imputed date of first use consistent with

reported age at first use and other drug use measures. The availability of an imputed date of first

use for each lifetime substance user enabled consideration of a more precise approach to

calculate substance use incidence rates. The new incidence rate calculation method accounts for

the fact that this person's age does not exactly intersect calendar time in whole years. Details on

the new methodology are reported by Gfroerer et al. (in press).

A.5.2 Impact on Incidence Rate Estimates

Incidence rate estimates are impacted by both the new editing and imputation procedures

and the incidence rate calculation method. To sort out the separate impacts of these two changes,

age-specific incidence rates were computed from the 1999 CAI data using three methods: (1)
107

new methodology using imputed data, (2) new methodology using edited data, and (3) old

methodology using imputed data.

The effect of the new editing and imputation procedures can be evaluated using the new

incidence rate calculation method and comparing the results from the fully imputed data (the

first two data columns) with the results from edited data only (the middle two data columns).

The annual estimates for marijuana in Table A.8 show 11 statistically significant differences for

youths aged 12 to 17, and 7 of the 11 differences were higher with imputation. At ages 18 to 25,

all six significant differences favor the imputed data. The general tendency was for incidence

rates based on fully edited and imputed data to be higher than those based on the older edit-only

approach. The average effects on marijuana incidence estimates for youths aged 12 to 17 were

58.3 with imputation and 57.3 with editing only, a relative increase of 1.5 percent (data not

shown). For persons aged 18 to 25, the averages were 40.8 with imputation and 39.9 with editing

only, a relative increase of 2.3 percent.

A second set of comparisons looked at the differences between the old and new method

of calculating age-specific rates using imputed data in both methods. This comparison illustrates

the difference in the two calculation methodologies holding the editing and imputation constant

(at the fully edited and imputed level). These differences based on 1999 CAI data are shown by

years in Table A.8 by comparing the first two data columns (new method - imputed variables)

with the last two data columns (old method - imputed variables).

The new methodology removed some of these borderline cases from the calculation of

the 18 to 25 age-specific rates and correctly placed them into the calculation of the 12 to 17

age-specific rates. Although both the numerator (new initiates) and the denominator (exposure

time) were influenced by the change in method, the main impact was through the classification

of initiates by age group in the numerator. Under the new method, new initiates were assigned to

an age group based on their attained age at the date of initiation. Under the old method, new

initiates were assigned to an age group based on their age at their birthday during the current

year. Under the old methodology, many of the 17-year-old initiates were being counted in the 18

to 25 age-specific rate. However, the new methodology placed them in a correct age group based

on their attained age at the date of initiation. On average, this resulted in an increase of almost 13

percent for marijuana incidence rates at ages 12 to 17 and a decrease of about 10 percent at ages

18 to 25 (data not shown).

A.5.3 Impact of the New Editing and Imputation Procedures

Table A.9 shows the impact of the new editing and imputation for 1999 CAI data on the

annual number of marijuana initiates and the mean age at first use for marijuana. Estimates
1 This comparison is partially confounded with respondent recall effects for surveys conducted in different

years. Sample sizes for 1999 PAPI data were not adequate to permit a meaningful comparison with 1999 CAI. Note

also that for each year beginning with 1994, only initiation prior to that year could be estimated using the PAPI data.

2

 The weights applied to the PAPI analysis were the initially computed and calibrated weights without any

adjustment to match the distribution of field interviewer experience to prior years.

108

based on 1994-1998 combined PAPI data are also presented in the table as an indication of the

overall impact of interview mode and revised editing and imputation procedures.1

Comparisons of the estimated numbers of marijuana initiates based on edited versus

imputed 1999 CAI showed an increase for the imputed data: 25 significant differences showing

higher marijuana estimates from imputed data. The multiyear average numbers of marijuana

initiates increased 2.4 percent (data not shown).

The impact of the 1999 editing and imputation procedures on estimates of average age at

first use were small and mixed. Comparisons against edited 1999 CAI data showed two

significant differences favoring the imputed data and six favoring the edited data for marijuana.

Multiyear averages showed a 0.02 percent increase in average age at first use for marijuana (data

not shown). In general, the relative impact of the 1999 imputation procedures on estimated

average age at first use was small relative to the impact on estimates of initiates or of incidence

rates. With so few significant differences and no correction for multiple comparisons, there is

little evidence for concluding any differences between the 1994-1998 PAPI data and the 1999

CAI data with respect to average age at first use.

A.5.4 Impact of Questionnaire Mode Change on Estimates of Marijuana Use Initiation

The changes in questionnaire mode (i.e., switching from the PAPI to the CAI

questionnaire in 1999) could affect the incidence rate estimates, including the fact that the CAI

instrument allowed for more internal consistency and more complete responses. In addition, the

format of the CAI questionnaire gave the respondent more privacy when answering sensitive

questions. The 1999 CAI data showed a higher level of inconsistent data (0.2 percent for

1994-1998 PAPI and 0.5 percent for 1999 CAI). This probably reflected the more

comprehensive editing for inconsistencies within the whole substance module employed with the

1999 CAI data. This increased rigor in the edit process produced an increase in inconsistencies

in spite of the programmed consistency checks within the CAI instrument.

Table A.10 displays the 12 to 17 and 18 to 25 age-specific incidence marijuana rates for

PAPI and CAI. Annual estimates are provided for PAPI combined data for 1994-1998, for 1999

PAPI data,2

 and for 1999 CAI data. For both PAPI and CAI, edited data and the old incidence

methodology were used to compute these estimates. For comparability, nonimputed edited data
109

was used because the PAPI data did not have imputed versions of the age at first use data. Only a

small number of years showed a significant difference between the CAI and PAPI estimates.

 Another way to deal with high variability in annual incidence estimates is to average the

annual estimates over several years. This approach found a 5.4 percent increase in CAI

marijuana estimates at ages 12 to 17 and a 1.2 percent decrease in CAI estimates at ages 18 to 25

(data not shown).

Even though the statistical results were mixed, there was evidence of some overall

increased reporting of drug use initiation under the CAI mode, which in turn increased estimates

of incidence rates. Any appreciable effect on mean age at first use could not be concluded.

A.5.5 Summary

 Although the estimates for individual years were quite variable, the overall average

impact of editing and imputation was to increase incidence rates for both age groups (12 to 17

and 18 to 25) and to increase the estimated number of new initiates. The new incidence rate

calculation rules treated respondents as 17 year olds right up (but not including ) their 18th

birthday. The old rule classified respondents as 18 year olds for the entire year in which their 18th

birthday occurred. This had the effect of increasing the estimates of time at risk and the number

of initiates for 17 year olds. However, because the number of initiates was high at age 17, the

overall impact was greater on the numerator than the denominator. As a result, the incidence

rates for youths aged 12 to 17 increased and the incidence rate for persons aged 18 to 25 usually

decreased somewhat.

Mode effects could not be cleanly isolated because of some accompanying changes in the

question routing process and supplementary questions on date of first use for recent users that

were implemented in conjunction with the implementation of CAI. One somewhat surprising

result was that the level of missing or inconsistent data actually increased with the introduction

of CAI. The increase in detected inconsistencies may have resulted because of the increased

number of checks employed to identify inconsistent data in the post-survey processing. The

increase in the proportion of missing age at first use data may have been facilitated by the

respondent's option to answer "don't know" or "refused." 

The overall impact of the conversion from PAPI to CAI was assessed by comparing the

results from the 1999 PAPI and CAI samples using the edited data. The old method of rate

calculation was applied to both samples for mode comparison purposes. Annual estimates were

highly variable, and few statistically significant differences were identified. 
110

The larger national sample sizes available since 1999 will help make the study of the

initiation of substance use more feasible and more precise. The revisions and corrections

introduced in the CAI questionnaire, in the coordinated editing and imputation procedures, and

in rate computation methodology in 1999 should also increase the utility of the survey data for

these purposes. Based on the analyses reported in this section, any comparisons of 1999 and

subsequent years' data with data from 1998 and prior years' data should either be avoided or

tempered with an understanding of the methodological effects reported earlier.
111

Table A.1 Summary of 2000 NHSDA Suppression Rules

Estimate Suppress if:

Prevalence rate, p, with

nominal sample size, n,

and design effect, deff

The estimated prevalence rate, p, is < 0.00005 or >0.99995, or

 when , or

 when , or

, or

where 

Note: The rounding portion of this suppression rule for prevalence rates will produce

some estimates that round at one decimal place to 0.0% or 100.0% but are not

suppressed from the tables.

Estimated number

(numerator of p)

The estimated prevalence rate, p, is suppressed. 

Note: In some instances when p is not suppressed, the estimated number may appear

as a 0 in the tables; this means that the estimate is >0 but <500 (estimated numbers are

shown in thousands).

Mean age at first use,

, with nominal

sample size, n

, or

Incidence rate, Rounds to < 0.1 per 1,000 person-years of exposure, or

Number of initiates, Rounds to <1,000 initiates, or

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
112

Table A.2 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by

Screening Result Code

Screening Result

1999 NHSDA 2000 NHSDA

Sample Size

Weighted

Percentage Sample Size

Weighted

Percentage

Total Sample 223,868 100.00 215,860 100.00

Ineligible cases 36,026 15.78 33,284 15.09

Eligible cases 187,842 84.22 182,576 84.91

Ineligibles 36,026 100.00 33,284 100.00

Vacant 18,034 49.71 16,796 50.76

Not a primary residence 4,516 12.90 4,506 13.26

Not a dwelling unit 4,626 12.70 3,173 9.33

All military personnel 482 1.22 414 1.21

Other, ineligible 8,368 23.46 8,395 25.43

Eligible Cases 187,842 100.00 182,576 100.00

Screening complete 169,166 89.63 169,769 92.84

No one selected 101,537 54.19 99,999 55.36

One selected 44,436 23.63 46,981 25.46

Two selected 23,193 11.82 22,789 12.03

Screening not complete 18,676 10.37 12,807 7.16

No one home 4,291 2.38 3,238 1.82

Respondent unavailable 651 0.36 415 0.24

Physically or mentally incompetent 419 0.24 310 0.16

Language barrier—Hispanic 102 0.06 83 0.05

Language barrier—other 486 0.28 434 0.27

Refusal 11,097 5.92 7,535 4.14

Other, access denied 1,536 1.08 748 0.45

Other, eligible 38 0.02 7 0.00

Other, problem case 56 0.03 37 0.02

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
113

Table A.3 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Persons Aged 12 or Older

Final Interview Code

1999 NHSDA 2000 NHSDA

Sample Size

Weighted

Percentage Sample Size

Weighted

Percentage

Total Selected Persons 89,883 100.00 91,961 100.00

Interview complete 66,706 68.55 71,764 73.93

No one at dwelling unit 1,795 2.13 1,776 2.02

Respondent unavailable 3,897 4.53 3,058 3.52

Breakoff 50 0.07 72 0.09

Physically/mentally incompetent 1,017 2.62 1,053 2.57

Language barrier—Spanish 168 0.12 109 0.08

Language barrier—Other 480 1.46 441 1.06

Refusal 11,276 17.98 10,109 14.99

Parental refusal 2,888 1.01 2,655 0.88

Other 1,606 1.53 924 0.86

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.

Table A.4 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Youths Aged 12 to 17

Final Interview Code

1999 NHSDA 2000 NHSDA

Sample Size

Weighted

Percentage Sample Size

Weighted

Percentage

Total Selected Persons 32,011 100.00 31,242 100.00

Interview complete 25,384 78.07 25,756 82.58

No one at dwelling unit 322 1.09 278 0.86

Respondent unavailable 872 3.04 617 2.05

Breakoff 13 0.03 18 0.05

Physically/mentally incompetent 244 0.76 234 0.76

Language barrier—Spanish 15 0.03 10 0.03

Language barrier—Other 58 0.18 50 0.20

Refusal 1,808 5.97 1,455 4.52

Parental refusal 2,885 9.50 2,641 8.35

Other 410 1.33 183 0.59

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
114

Table A.5 Weighted Percentages and Sample Sizes for 1999 and 2000 NHSDAs, by Final

Interview Code, among Persons Aged 18 or Older

Final Interview Code

1999 NHSDA 2000 NHSDA

Sample Size

Weighted

Percentage Sample Size

Weighted

Percentage

Total Selected Persons 57,872 100.00 60,719 100.00 

Interview complete 41,322 67.41 46,008 72.92

No one at dwelling unit 1,473 2.25 1,498 2.16

Respondent unavailable 3,025 4.71 2,441 3.69

Breakoff 37 0.07 54 0.09

Physically/mentally incompetent 773 2.85 819 2.78

Language barrier—Spanish 153 0.13 99 0.09

Language barrier—Other 422 1.62 391 1.16

Refusal 9,468 19.41 8,654 16.22

Parental refusal 3 0.00 14 0.01

Other 1,196 1.55 741 0.89

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
115

Table A.6 Response Rates and Sample Sizes for the 1999 and 2000 NHSDAs, by Demographic Character

1999 NHSDA 2000 NH

Selected

Persons 

Completed

Interviews

Weighted

Response

Rate

Selected

Persons 

Complet

Interview

Total 89,883 66,706 68.55% 91,961 71,764 Age in Years

12-17 32,011 25,384 78.07% 31,242 25,756 18-25 30,439 22,151 71.21% 29,424 22,849 26 or older 27,433 19,171 66.76% 31,295 23,159 

Gender

Male 43,883 31,987 67.12% 44,899 34,375 Female 46,000 34,719 69.81% 47,062 37,389 

Race/Ethnicity

Hispanic 11,203 8,755 74.59% 11,454 9,396 White 63,211 46,272 67.98% 64,517 49,631 Black 10,552 8,044 70.39% 10,740 8,638 All other races 4,917 3,635 59.28% 5,250 4,099 

Region

Northeast 16,794 11,830 64.03% 18,959 14,394 Midwest 24,885 18,103 69.63% 25,428 19,355 South 27,390 21,018 70.93% 27,217 22,041 West 20,814 15,755 67.47% 20,357 15,974 

County Type

Large metropolitan 36,101 25,901 65.15% 37,754 28,744 Small metropolitan 30,642 22,612 69.98% 31,400 24,579 Nonmetropolitan 23,140 18,193 74.97% 22,807 18,441 

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
116

Table A.7 Comparison of Initiation Rates, by Year of Initiation and Survey Year

Year of Initiation Average

of Ratio

of 1-Year

Recall to

2-Year

Recall

1993 1994 1995 1996

Year of Survey

1994 1995 1995 1996 1996 1997 1997 1998

Rate for Age 12 to 17

Marijuana 59.2 53.7 74.2 75.2 75.7 73.6 83.2 75.6 1.055

Cocaine 8.9 5.0 10.2 5.7 10.6 8.0 11.3 11.0 1.480

Heroin 0.7 0.5 2.1 1.4 2.5 1.8 3.9 1.5 1.722

Rate for Age 18 to 25

Marijuana 46.9 41.4 42.1 55.9 47.7 53.4 53.6 50.5 0.960

Cocaine 12.8 12.8 9.9 11.8 13.8 14.7 14.8 13.9 0.961

Heroin 0.1 1.4 1.4 2.1 2.4 1.9 2.3 3.0 0.692

Number of Initiates

Marijuana 2,035 1,783 2,251 2,548 2,368 2,443 2,540 2,384 1.015

Cocaine 595 538 533 530 652 654 675 664 1.031

Heroin 41 62 122 97 141 93 171 127 1.195

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1994-1998.
117

Table A.8 Marijuana Annual Age-Specific Rates at First Use Per 1,000 Person-Years of

Exposure: 1999

Year

New Method -

Imputed Variable

New Method -

Edited Variable

Old Method -

Imputed Variable

12-17 18-25 12-17 18-25 12-17 18-25

1965 9.6 7.5 8.9 6.7 9.1 7.7

1966 19.3 32.1 19.5b 32.1 17.9 32.6

1967 20.7 30.8 20.6 30.9 19.1 29.4

1968 20.3 43.5 20.2 41.2 16.3 44.6

1969 34.1 56.7 34.5b 56.4 29.2b 55.7

1970 55.8 47.7 55.0 46.7 49.1b 50.9

1971 46.7 49.7 46.2 48.5 41.8a 54.0a

1972 59.7 50.2 59.7 47.8a 54.3b 52.7

1973 59.0 39.4 59.6a 36.8 53.3b 43.5a

1974 66.6 53.0 65.6 52.4 56.6b 62.2b

1975 65.3 53.7 63.6 53.4 58.3b 56.8

1976 76.5 60.5 75.4 60.1 63.2b 72.3b

1977 86.5 51.2 86.5 50.0 77.9b 57.8a

1978 84.2 49.6 81.7 48.8 75.0b 56.7

1979 86.3 54.5 84.2 54.4 75.7b 63.2b

1980 75.9 48.2 75.5 44.6 66.6b 53.3

1981 51.8 35.1 51.3 35.0 50.1 36.3

1982 59.0 36.3 59.5b 35.1 51.9b 40.7a

1983 55.3 33.1 53.1a 32.5 48.5b 38.8b

1984 58.5 38.5 58.5 38.3 52.1b 43.7b

1985 58.4 38.7 57.8 37.2 51.8b 44.9b

1986 53.2 29.8 53.3 28.4a 47.6b 33.7a

1987 56.1 37.3 54.3 36.7 49.8b 42.4b

1988 55.7 31.6 54.6a 31.4 49.4b 33.1

1989 46.7 26.8 46.2 25.8 40.2b 32.2b

1990 48.4 29.0 48.2 28.6 42.5b 32.7a

1991 46.1 31.9 45.6 31.4 39.5b 37.5b

1992 51.0 30.5 50.4 29.5a 45.7b 34.2b

1993 60.0 36.7 59.7 36.3 53.4b 41.5b

1994 74.3 42.1 72.9b 41.2 67.2b 47.1b

1995 78.3 46.1 76.7b 45.6 70.8b 53.1b

1996 89.9 44.1 87.7b 42.7b 80.0b 52.8b

1997 90.0 45.1 87.3b 44.5a 79.6b 53.8b

1998 82.6 46.5 79.2b 45.6b 73.5b 54.5b

Note: The numerator of each rate is the number of persons in the age group who first used the drug in the year,

while the denominator is the person-time exposure measured in thousands of years. a

 Difference between the estimate and New Method - Imputed is statistically significant at the 0.05 level. b

 Difference between the estimate and New Method - Imputed is statistically significant at the 0.01 level.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999.
118

Table A.9 Comparison of Numbers of Marijuana Initiates (in Thousands) and Mean Age at

First Marijuana Use: 1994-1998 PAPI Versus 1999 CAI

Year

Initiates (1,000s) Mean Age (Years)

1994-1998

PAPI

1999 CAIEdited Data

1999 CAIImputed

Data

1994-1998

PAPI

1999 CAIEdited

Data

1999 CAIImputed Data

1965 601 442 478 18.95 21.77 21.61

1966 977 1,229 1,234 20.05 18.68 18.68

1967 1,423 1,199 1,210 19.76 18.92 18.91

1968 1,621 1,470 1,533 18.97 18.89 18.91

1969 2,245 2,301 2,317 19.19 19.43 19.43

1970 2,611 2,501a 2,585 19.21 18.20 18.34

1971 2,710 2,403 2,456 18.78 17.87 17.84

1972 2,861 2,676b 2,747 18.62 18.16a 18.24

1973 2,897 2,610a 2,697 18.28 19.03 19.15

1974 2,966 2,873b 2,938 18.50 17.85 17.82

1975 3,128 2,923a 2,989 18.51 18.90a 18.84

1976 2,786 3,216 3,267 18.69 18.38 18.34

1977 2,889 3,195a 3,251 18.95 18.03 18.07

1978 2,846 2,959a 3,046 17.77 18.14 18.10

1979 2,654 2,983b 3,052 18.22 18.22 18.18

1980 2,499 2,564a 2,680 18.41 18.13 18.38

1981 2,115 1,820a 1,840 17.94 18.29 18.26

1982 1,964 2,056a 2,090 18.19 18.85 18.98

1983 2,143 1,889b 1,954 17.85 18.90a 18.77

1984 2,010 2,029 2,040 19.19 18.56 18.54

1985 1,775 1,890a 1,938 17.85 18.05 18.03

1986 1,845 1,604b 1,633 19.32 17.15 17.18

1987 1,756 1,708b 1,763 17.92 17.48 17.45

1988 1,565 1,595a 1,620 17.49 17.49a 17.47

1989 1,371 1,353a 1,388 17.87 17.21 17.29

1990 1,423 1,451a 1,470 17.66 17.42 17.44

1991 1,415 1,519b 1,545 17.47 17.78 17.76

1992 1,644 1,544b 1,578 17.60b 16.49 16.49

1993 1,983 1,930b 1,972 16.96 17.33 17.45

1994 2,380 2,235b 2,293 16.90 16.61 16.59

1995 2,409 2,359b 2,421 16.57 16.65b 16.59

1996 2,462 2,532b 2,616 16.62 17.24b 17.18

1997 2,114b 2,493b 2,571 17.09 17.16b 17.08

1998 -- 2,345b 2,437 -- 17.63b 17.52

-- Not available.

a

 Difference between the estimate and 1999 CAI-Imputed is statistically significant at the 0.05 level.

b

 Difference between the estimate and 1999 CAI-Imputed is statistically significant at the 0.01 level.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1994-1998 PAPI and

1999 CAI.
119

Table A.10 Comparison of Mode Effect: Marijuana Annual Age-Specific Rates at First Use Per

1,000 Person-Years of Exposure with PAPI and CAI Data

Year

PAPI 1994-1998

PAPI 1999 Old Method -

Edited CAI 1999 Old Method - Edited

12-17 18-25 12-17 18-25 12-17 18-25

1965 8.7 13.7a 11.8 13.8 8.4 6.9

1966 13.9 23.5 7.4a 38.8 18.1 32.6

1967 15.6 38.8 18.4 36.7 18.9 29.5

1968 20.1 45.2 35.0a 47.0 16.2 42.5

1969 31.7 54.1 29.0 50.9 29.5 55.3

1970 35.1 64.3 27.1a 50.1 48.3 50.5

1971 40.8 65.9 41.6 49.3 41.4 52.8

1972 48.4 64.1 44.3 69.4 54.5 50.5

1973 60.2 57.7a 52.4 68.0 54.1 40.8

1974 57.6 61.7 68.7 58.0 55.4 61.7

1975 67.8 57.8 48.7 43.7 56.7 56.4

1976 59.5 52.4a 74.0 61.0 62.2 72.1

1977 66.7 50.2 34.5b 58.5 77.8 56.8

1978 75.2 49.9 62.2 61.1 74.9 53.1

1979 60.6 59.0 63.5 45.6 73.7 62.9

1980 59.2 56.0 58.0 47.9 66.4 49.9

1981 54.3 43.1 54.4 69.2a 49.6 36.3

1982 48.2 42.3 55.8 35.5 52.2 39.6

1983 56.4a 45.1 52.1 39.9 46.3 38.2

1984 53.1 38.4 54.3 28.4a 52.2 43.6

1985 48.8 38.6 52.6 37.9 51.2 43.4

1986 48.4 41.3a 38.4 43.4 47.7 32.3

1987 48.4 40.5 41.6 29.8 48.1 41.7

1988 44.9 36.9 39.8 29.3 48.5 32.9

1989 37.0 32.8 38.1 40.4 40.0 31.1

1990 36.9 36.6 38.9 33.8 42.3 32.3

1991 38.4 34.0 45.4 23.3a 39.0 37.0

1992 44.5 37.0 44.7 25.4 45.2 33.5

1993 55.1 45.9 65.3 39.1 53.1 41.2

1994 72.8 47.9 76.7 41.7 66.0 46.1

1995 74.1 52.6 72.5 47.7 69.1 52.5

1996 79.3 52.1 56.3b 56.8 77.9 51.3

1997 64.4a 47.1 84.4 57.5 76.9 53.2

1998 -- -- 55.2a 53.5 70.2 53.2

-- Not available.

a

 Difference between PAPI and CAI is statistically significant at the 0.05 level.

b

 Difference between PAPI and CAI is statistically significant at the 0.01 level.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1994-1998 PAPI and

1999 CAI.
120
121

Appendix B: Selected Standard Error Tables
122
123

Table 3.1S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First

Used Marijuana During the Years 1965 to 1999, Their Mean Age at First Use,

and the Annual Incidence Rates of First Use (Per 1,000 Person-Years of

Exposure), for All Ages

Year Number of Initiates (1,000s) Mean Age at First Use Incidence Rates1

1965 75 1.2 0.5

1966 114 0.5 0.8

1967 119 0.4 0.8

1968 136 0.4 0.9

1969 147 0.3 1.0

1970 164 0.3 1.1

1971 158 0.3 1.0

1972 157 0.3 1.0

1973 154 0.4 1.0

1974 150 0.3 1.0

1975 150 0.4 1.0

1976 163 0.3 1.1

1977 157 0.3 1.0

1978 162 0.3 1.0

1979 144 0.3 1.0

1980 127 0.5 0.8

1981 97 0.3 0.6

1982 101 0.5 0.6

1983 101 0.6 0.6

1984 95 0.4 0.6

1985 85 0.4 0.5

1986 74 0.3 0.4

1987 71 0.3 0.4

1988 73 0.2 0.4

1989 67 0.4 0.4

1990 59 0.6 0.4

1991 62 0.5 0.4

1992 54 0.2 0.3

1993 58 0.3 0.4

1994 63 0.2 0.4

1995 56 0.1 0.4

1996 66 0.3 0.4

1997 59 0.3 0.4

1998 61 0.4 0.4

19992 61 0.2 0.4

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
124

Table 3.2S Standard Errors of Estimated Age-Gender Numbers (in Thousands) of

Persons Who First Used Marijuana During the Years 1965 to 1999

Year

Number of Initiates (1,000s)

Males

12-14

Females

12-14

Males

15-17

Females

15-17

Males

18-20

Females

18-20

Males

21+

Females

21+

1965 19 * 42 17 19 30 21 33

1966 22 * 42 32 66 44 42 39

1967 32 26 40 28 54 41 60 34

1968 27 16 47 26 83 47 69 51

1969 26 25 63 41 75 53 50 64

1970 38 43 64 51 67 46 62 51

1971 52 41 53 42 66 44 60 71

1972 48 31 82 61 56 40 57 59

1973 47 37 65 48 56 44 63 63

1974 40 45 68 56 45 49 50 56

1975 43 51 55 59 58 42 45 63

1976 38 34 84 69 62 45 53 63

1977 45 38 69 67 56 52 49 52

1978 41 40 79 68 42 54 45 55

1979 42 29 66 67 62 45 34 46

1980 24 20 61 54 36 50 47 49

1981 24 18 44 39 38 39 29 37

1982 24 19 37 37 41 38 46 47

1983 25 19 37 29 32 28 59 28

1984 29 21 34 31 32 26 39 40

1985 24 21 34 30 28 26 39 28

1986 19 17 33 33 26 22 30 25

1987 11 14 32 33 27 22 20 29

1988 14 9 36 31 24 19 31 33

1989 12 10 33 25 23 23 27 22

1990 12 10 28 19 24 18 21 30

1991 16 10 20 19 25 21 39 17

1992 14 14 21 17 23 19 19 17

1993 16 17 19 22 21 19 20 22

1994 18 19 24 22 17 22 25 17

1995 19 16 24 20 16 17 19 17

1996 17 16 26 25 17 17 18 28

1997 16 15 24 23 19 16 21 19

1998 17 14 23 20 17 18 31 19

19991 20 18 28 24 17 19 22 27

* Low precision; no estimate reported.

1

 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
125

Table 3.3S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First Used

Marijuana During the Years 1965 to 1999, Their Mean Age at First Use, and the

Annual Incidence Rates of First Use (Per 1,000 Person-Years of Exposure), by

Gender

Number of Initiates

(1,000s) Mean Age at First Use Incidence Rates1

Year Males Females Males Females Males Females

1965 55 50 0.8 2.4 0.9 0.7

1966 92 70 0.5 0.9 1.4 0.9

1967 97 67 0.4 1.0 1.5 0.9

1968 122 76 0.4 1.0 1.8 1.0

1969 110 101 0.4 0.5 1.6 1.3

1970 123 94 0.4 0.5 1.8 1.2

1971 124 102 0.4 0.5 1.8 1.3

1972 126 101 0.5 0.4 1.8 1.3

1973 115 105 0.5 0.5 1.7 1.3

1974 106 105 0.4 0.4 1.6 1.3

1975 105 107 0.5 0.5 1.6 1.3

1976 122 111 0.3 0.4 1.7 1.4

1977 110 107 0.4 0.4 1.6 1.3

1978 107 114 0.4 0.5 1.5 1.4

1979 107 97 0.4 0.5 1.5 1.2

1980 85 93 0.8 0.6 1.2 1.1

1981 68 70 0.4 0.5 1.0 0.8

1982 77 72 0.7 0.6 1.1 0.9

1983 79 57 1.0 0.4 1.1 0.7

1984 68 61 0.8 0.4 0.9 0.7

1985 65 54 0.5 0.6 0.9 0.6

1986 55 50 0.4 0.3 0.7 0.6

1987 47 51 0.4 0.4 0.6 0.6

1988 56 50 0.3 0.3 0.7 0.6

1989 49 41 0.6 0.4 0.6 0.5

1990 42 42 0.5 1.3 0.6 0.5

1991 54 33 0.8 0.4 0.7 0.4

1992 38 34 0.2 0.2 0.5 0.4

1993 37 43 0.3 0.4 0.5 0.5

1994 44 42 0.4 0.2 0.6 0.5

1995 39 37 0.1 0.1 0.6 0.4

1996 42 46 0.2 0.5 0.6 0.6

1997 41 36 0.4 0.3 0.6 0.5

1998 48 36 0.7 0.3 0.7 0.5

19992 44 44 0.2 0.4 0.7 0.6

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
126

Table 3.4S Standard Errors of Estimated Annual Age-Gender Specific Incidence Rates

of First Use (Per 1,000 Person-Years of Exposure) of Persons Who First Used

Marijuana During the Years 1965 to 1999

Year

Age-Gender Specific Incidence Rates1

Males

12-14

Females

12-14

Males

15-17

Females

15-17

Males

18-20

Females

18-20

Males

21+

Females

21+

1965 3.3 * 7.9 2.7 4.9 5.6 0.9 1.1

1966 3.9 * 8.0 5.5 15.0 7.5 1.7 1.3

1967 5.7 4.2 7.5 4.9 11.9 6.5 2.4 1.1

1968 4.7 2.5 9.0 4.4 18.4 8.3 2.6 1.5

1969 4.4 3.8 12.1 7.2 18.4 10.1 1.8 1.8

1970 5.9 6.5 12.1 8.9 16.4 9.1 2.2 1.4

1971 8.0 6.4 11.1 7.3 17.5 8.9 2.1 1.8

1972 7.9 4.6 16.1 10.4 14.8 8.8 1.9 1.5

1973 8.0 5.5 12.8 8.3 15.3 9.1 2.0 1.5

1974 6.6 7.0 14.2 10.1 12.7 10.5 1.6 1.3

1975 6.9 8.2 11.9 10.8 15.8 9.3 1.4 1.5

1976 6.0 5.7 17.5 12.4 16.5 10.4 1.6 1.4

1977 7.6 6.1 14.2 12.9 16.7 12.5 1.4 1.1

1978 7.5 6.8 16.0 13.5 13.3 13.1 1.3 1.2

1979 8.2 5.1 14.3 13.4 19.8 11.0 1.0 1.0

1980 4.9 3.7 13.9 11.2 11.2 13.1 1.3 1.0

1981 4.6 3.4 10.4 8.1 10.9 10.3 0.8 0.8

1982 4.6 3.3 9.2 7.9 11.8 10.3 1.2 0.9

1983 4.8 3.4 9.1 6.2 9.8 7.5 1.5 0.5

1984 5.5 3.8 8.0 6.6 9.8 6.8 1.0 0.8

1985 5.0 3.8 7.8 6.5 8.7 6.8 1.0 0.5

1986 4.1 3.5 7.5 6.9 8.0 5.6 0.7 0.5

1987 2.5 2.9 7.7 6.9 8.2 5.9 0.5 0.5

1988 3.1 1.8 8.7 6.8 7.1 5.1 0.7 0.6

1989 2.5 1.9 8.2 5.7 6.9 5.8 0.6 0.4

1990 2.5 2.1 7.3 4.4 7.1 4.7 0.5 0.5

1991 3.2 1.8 5.2 4.5 7.8 5.5 0.8 0.3

1992 2.7 2.6 5.1 3.9 7.5 5.2 0.4 0.3

1993 3.0 3.0 4.7 4.9 6.8 5.1 0.4 0.4

1994 3.2 3.4 5.8 4.9 5.6 6.1 0.5 0.3

1995 3.3 2.9 5.6 4.5 5.4 5.0 0.4 0.3

1996 3.1 2.8 6.0 5.6 5.8 5.2 0.4 0.4

1997 2.9 2.8 5.5 5.1 6.9 4.6 0.4 0.3

1998 2.9 2.6 5.6 4.6 5.7 5.6 0.6 0.3

19992 3.5 3.4 7.1 5.9 5.8 5.5 0.4 0.4

* Low precision; no estimate reported.

1

 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2

 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
127

Table 3.5S Standard Errors of Estimated Numbers (in Thousands) of Persons Who First

Used Marijuana During the Years 1965 to 1999, by Racial/Ethnic Subgroups

Year

Number of Initiates (1,000s)

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 57 * * * * *

1966 102 42 * * * *

1967 111 35 22 * * *

1968 115 63 26 * * *

1969 139 37 30 * * *

1970 152 41 22 18 * 10

1971 139 46 42 * 7 *

1972 144 47 35 5 8 8

1973 148 46 24 * * *

1974 137 41 50 5 * 8

1975 137 49 34 6 * *

1976 153 53 37 * 12 *

1977 140 49 37 26 * 12

1978 141 46 44 32 * 6

1979 125 52 28 * 3 7

1980 114 43 30 * * *

1981 89 33 24 * 3 *

1982 92 32 31 * 7 3

1983 90 23 32 18 5 *

1984 80 37 16 * 3 2

1985 71 24 28 20 3 5

1986 63 26 22 8 8 6

1987 63 21 20 22 4 4

1988 66 19 26 8 10 6

1989 57 18 25 9 * 4

1990 51 21 21 16 3 2

1991 55 20 16 15 5 5

1992 46 22 18 7 4 7

1993 47 22 18 8 7 5

1994 52 25 19 7 6 5

1995 47 20 17 10 3 6

1996 53 22 21 13 4 6

1997 48 25 20 7 5 6

1998 51 19 20 12 4 6

19991 54 23 21 10 8 7 1 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
128

Table 3.6S Standard Errors of Estimated Mean Ages at First Use of Persons Who First

Used Marijuana During the Years 1965 to 1999, by Racial/Ethnic Subgroups 

Year

Mean Age at First Use

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 1.5 * * * * *

1966 0.5 1.6 * * * *

1967 0.5 0.9 2.9 * * *

1968 0.5 0.8 3.0 * * *

1969 0.4 0.8 2.1 * * *

1970 0.3 1.2 0.4 0.8 * *

1971 0.4 1.7 0.8 * * *

1972 0.4 0.7 1.8 * 1.4 *

1973 0.4 1.3 1.7 * * *

1974 0.3 1.3 0.8 * * 1.0

1975 0.4 0.6 1.1 * * *

1976 0.3 1.1 0.7 * 1.0 0.6

1977 0.4 0.6 0.9 0.3 0.9 *

1978 0.4 0.6 1.7 1.4 * *

1979 0.4 0.7 0.5 * 0.8 1.0

1980 0.6 1.2 1.0 0.8 * *

1981 0.4 1.3 0.7 * * *

1982 0.5 1.7 0.6 * 2.2 *

1983 0.7 1.0 1.1 1.1 1.9 1.1

1984 0.3 2.2 0.4 7.6 2.4 1.1

1985 0.5 0.6 0.8 1.3 0.7 1.6

1986 0.3 0.5 0.7 0.4 0.5 1.4

1987 0.4 0.5 0.6 1.4 2.5 2.8

1988 0.2 0.4 1.2 1.2 2.4 0.6

1989 0.5 0.4 0.6 1.5 0.6 1.2

1990 0.8 0.7 0.9 0.7 2.2 0.8

1991 0.6 0.4 0.4 0.9 2.9 0.7

1992 0.2 0.4 0.4 0.7 0.9 0.7

1993 0.3 1.1 0.4 1.9 4.7 0.4

1994 0.3 0.3 0.3 0.4 0.5 0.6

1995 0.1 0.3 0.3 1.1 0.5 0.3

1996 0.4 0.4 0.5 0.6 0.6 0.7

1997 0.4 0.7 0.3 0.5 0.9 0.4

1998 0.6 0.3 0.3 1.0 0.8 0.9

19991 0.3 0.3 0.4 1.4 0.7 0.9

* Low precision; no estimate reported.

1 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
129

Table 3.7S Standard Errors of Estimated Annual Incidence Rates of First Use (Per 1,000

Person-Years of Exposure) of Persons Who First Used Marijuana During the

Years 1965 to 1999, by Racial/Ethnic Subgroups

Year

Racial/Ethnic Specific Incidence Rates1

White Black Hispanic

Asian / Pacific

Islander / Native

Hawaiian

American

Indian /

Alaska Native

More Than

One Race

1965 0.5 * * * * *

1966 1.0 3.0 * * * *

1967 1.0 2.4 1.8 * * *

1968 1.0 4.2 2.0 * * *

1969 1.2 2.5 2.3 * * *

1970 1.4 2.6 1.7 3.5 * 10.6

1971 1.2 3.0 3.0 * 9.9 *

1972 1.3 3.0 2.4 0.8 12.3 8.0

1973 1.3 2.9 1.6 * * *

1974 1.2 2.6 3.3 0.9 * 7.7

1975 1.2 3.0 2.3 0.9 * *

1976 1.4 3.2 2.4 * 15.9 16.9

1977 1.3 3.0 2.3 4.1 * 11.5

1978 1.2 2.8 2.7 5.1 * 5.4

1979 1.1 3.1 1.6 * 4.2 6.4

1980 1.0 2.5 1.8 * * *

1981 0.8 1.9 1.4 * * *

1982 0.8 1.8 1.7 * 9.3 2.8

1983 0.8 1.3 1.7 2.7 6.4 *

1984 0.7 2.0 0.9 * 4.2 2.0

1985 0.6 1.2 1.5 2.8 3.9 3.8

1986 0.5 1.4 1.1 1.1 9.9 4.3

1987 0.5 1.1 1.0 2.9 5.1 3.1

1988 0.6 1.0 1.3 1.1 12.3 4.2

1989 0.5 0.9 1.3 1.2 * 3.2

1990 0.4 1.1 1.1 2.2 3.9 1.3

1991 0.5 1.0 0.8 2.1 6.9 3.6

1992 0.4 1.1 0.9 1.0 5.3 5.4

1993 0.4 1.2 0.9 1.2 9.2 3.9

1994 0.5 1.3 1.1 1.1 7.7 3.9

1995 0.4 1.1 1.0 1.4 4.4 4.7

1996 0.5 1.2 1.2 1.9 5.2 5.2

1997 0.5 1.4 1.1 1.0 6.7 5.0

1998 0.5 1.1 1.1 1.7 6.3 5.2

19992 0.5 1.3 1.2 1.4 14.8 6.8

* Low precision; no estimate reported.

1 The numerator of each rate is the number of persons who first used marijuana in the year, while the denominator is the

person-time exposure measured in thousands of years. 2 Estimated using 2000 data only.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
130

Table 6.1S Standard Errors and Suppression Rule for Percentages with Lifetime and Past Year Use of He

Psychotherapeutics among Adults Aged 26 or Older, by Age at First Marijuana Use and Age G

AgeinYears

Age of

Marijuana

Initiation in

Years

Heroin Cocaine 

Lifetime Past Year Lifetime Past Year Lifeti

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Su

Total 14 or younger 0.81 0 0.23 0 1.28 0 0.63 0 1.24 

15-17 0.43 0 0.08 0 0.89 0 0.31 0 0.89 18-20 0.46 0 0.07 0 1.06 0 0.32 0 1.00 21 or older 0.35 0 0.11 0 0.94 0 0.18 0 1.09 Never usedmarijuana 0.02 0 0.00 0 0.06 0 0.01 0 0.20 

26-34 14 or younger 0.62 0 0.05 0 1.39 0 0.82 0 1.39 

15-17 0.37 0 0.14 0 0.97 0 0.44 0 0.96 18-20 0.29 0 0.07 0 1.17 0 0.41 0 1.16 21 or older 0.41 0 0.00 1 1.53 0 0.43 0 1.54 Never usedmarijuana 0.03 0 0.01 0 0.12 0 0.03 0 0.32 

35-49 14 or younger 1.24 0 0.39 0 1.85 0 0.88 0 1.89 

15-17 0.56 0 0.10 0 1.26 0 0.40 0 1.23 18-20 0.57 0 0.10 0 1.45 0 0.40 0 1.29 21 or older 0.35 0 0.30 0 1.58 0 0.47 0 1.51 Never usedmarijuana 0.05 0 0.00 1 0.17 0 0.04 0 0.38 

50+ 17 or younger 5.27 1 0.00 1 6.69 1 2.94 1 6.64 

18-20 1.79 0 0.19 0 3.50 0 1.09 0 3.20 21 or older 0.65 0 0.00 1 1.39 0 0.10 0 1.78 Never usedmarijuana 0.02 0 0.01 0 0.06 0 0.01 0 0.27 

Note:Nonmedical use of any prescription-type psychotherapeutic indicates using pain relievers, tranquilizers, stimulants, or sedatives at least once. In

counter drugs.

1 1 = estimate should be suppressed due to low precision based either on small sample size or extreme variance; 0 = no suppression.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
131

Table 6.2S Standard Errors and Suppression Rule for Percentages with Past Year

Heavy Marijuana Use and Heavy Use of Other Illicit Drugs among Adults

Aged 26 or Older, by Age at First Marijuana Use and Age Groups: 1999

and 2000

Age in Years

Age of Marijuana

Initiation in Years

Heavy Marijuana Use

Heavy Use of Other Illicit

Drugs

Standard Error Suppression1 Standard Error Suppression1

Total 14 or younger 0.51 0 0.61 0

15-17 0.17 0 0.29 0

18-20 0.12 0 0.28 0

21 or older 0.21 0 0.21 0

Never used marijuana 0.00 1 0.06 0

26-34 14 or younger 0.79 0 0.75 0

15-17 0.28 0 0.40 0

18-20 0.30 0 0.31 0

21 or older 0.25 0 0.49 0

Never used marijuana 0.00 1 0.10 0

35-49 14 or younger 0.64 0 0.86 0

15-17 0.22 0 0.37 0

18-20 0.14 0 0.42 0

21 or older 0.38 0 0.49 0

Never used marijuana 0.00 1 0.12 0

50+ 17 or younger 0.00 1 2.84 0

18-20 0.12 0 0.52 0

21 or older 0.30 0 0.20 0

Never used marijuana 0.00 1 0.09 0

Note: Heavy marijuana use refers to using marijuana on 300 or more days in the past year. Heavy use of other

illicit drugs refers to using cocaine, hallucinogens, inhalants, heroin, or any prescription-type

psychotherapeutic used nonmedically (i.e., pain relievers, sedatives, tranquilizers, or stimulants) on at

least 50 days in the past year. 1 1 = estimate should be suppressed because of low precision based either on small sample size or extreme

variance; 0 = no suppression.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 1999 and 2000.
132

Table 6.3S Standard Errors and Suppression Rule for Percentages with Past Year Alcohol and/or Illicit Drug Depen

Adults Aged 26 or Older, by Age at First Marijuana Use and Age Groups: 2000

AgeinYears

Age of

Marijuana

Initiation in

Years

Illicit Drug Dependence

or Abuse

Alcohol or Illicit Drug

Dependence or Abuse Alcohol Dependence Illicit Drug Dependence Marijuana Dep

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Suppression1

Standard

Error Supp

Total 14 or younger 0.84 0 1.28 0 0.78 0 0.73 0 0.58 

15-17 0.36 0 0.67 0 0.43 0 0.25 0 0.19 18-20 0.48 0 0.75 0 0.60 0 0.47 0 0.25 21 or older 0.33 0 0.91 0 0.65 0 0.25 0 0.13 Never usedmarijuana 0.04 0 0.17 0 0.12 0 0.04 0 0.00 

26-34 14 or younger 1.02 0 1.48 0 0.87 0 0.90 0 0.73 

15-17 0.47 0 0.98 0 0.60 0 0.34 0 0.20 18-20 0.42 0 1.23 0 0.77 0 0.29 0 0.19 21 or older 1.07 0 1.99 0 1.17 0 0.47 0 0.47 Never usedmarijuana 0.11 0 0.31 0 0.18 0 0.10 0 0.00 

35-49 14 or younger 1.13 0 1.85 0 1.08 0 0.97 0 0.79 

15-17 0.38 0 0.86 0 0.59 0 0.35 0 0.27 18-20 0.58 0 1.01 0 0.77 0 0.57 0 0.40 21 or older 0.69 0 1.48 0 1.13 0 0.57 0 0.00 Never usedmarijuana 0.10 0 0.37 0 0.28 0 0.10 0 0.00 

50+ 17 or younger 5.30 1 5.37 1 3.29 1 3.15 1 0.00 

18-20 1.76 1 2.12 0 1.85 0 1.71 1 0.34 21 or older 0.29 0 1.29 0 0.92 0 0.28 0 0.22 Never usedmarijuana 0.05 0 0.24 0 0.15 0 0.04 0 0.00 

Note: Illicit drug dependence or abuse indicates dependence on or abuse of at least one of the following drugs: marijuana/hashish, cocaine (including 

(including LSD and PCP), inhalants, or any prescription-type psychotherapeutic used nonmedically. Other illicit drug dependence indicates m

least one of the following drugs: cocaine, hallucinogens, inhalants, heroin, pain relievers, sedatives, tranquilizers, or stimulants. Dependence ofound in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV).

1 1 = estimate should be suppressed because of low precision based either on small sample size or extreme variance; 0 = no suppression.

Source: SAMHSA, Office of Applied Studies, National Household Survey on Drug Abuse, 2000.
133

Appendix C: Selected Questionnaire Pages (1999 and 2000

NHSDAs)
134
135

Selected Demographic and Marijuana Questions from the

1999 National Household Survey on Drug Abuse:

Specifications for Programming

Core Demographics

LANG INTERVIEWER: SELECT THE LANGUAGE TO BE USED IN THIS INTERVIEW.

1 ENGLISH

2 SPANISH

3 MULTIMEDIA LANGUAGE

NHSDA CAI Instrument Version 3.2

NOTE1 INTERVIEWER: DO NOT READ ALOUD UNLESS RESPONDENT QUESTIONS THE BURDEN ASSOCIATED

WITH THIS INTERVIEW.

NOTICE: Public reporting for this collection of information is estimated to average 55 minutes per response, including

the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and

completing and reviewing the collection of information. Send comments regarding this burden estimate or any other

aspect of this collection of information, including suggestions for reducing this burden, to SAMHSA Reports

Clearance Officer, Paperwork Reduction Project (0930-0110); Room 16-105; Parklawn Building; 5600 Fishers Lane;

Rockville, MD 20857. An agency may not conduct or sponsor, and a person is not required to respond to a collection

of information unless it displays a currently valid OMB control number. The OMB control number for this project is

0930-0110.

REMINDFI INTERVIEWER: IF YOU HAVE NOT FULLY INFORMED THIS RESPONDENT ABOUT WHAT

PARTICIPATION IN THIS STUDY ENTAILS, REFER TO THE INFORMATION IN YOUR

SHOWCARD BOOKLET. WHEN RESPONDENT IS FULLY INFORMED, CONTINUE WITH THE

INTERVIEW.

PRESS [ENTER] TO CONTINUE.

AGE1 What is your date of birth?

ENTER MM-DD-YYYY

DEFINE CALCAGE:

CALCAGE = AGE CALCULATED BY "SUBTRACTING" DATE OF BIRTH FROM DATE OF

INTERVIEW.

CONFIRM That would make you [CALCAGE] years old. Is this correct?

1 YES

2 NO

DK/REF

UNDER12 [IF CONFIRM = 1 OR DK/REF AND CALCAGE < 12] Since you are [CALCAGE] years old, we cannot

interview you for this study. Thank you for your cooperation. PROGRAM SHOULD ROUTE TO

ENDAUDIO

FIXAGE [IF CONFIRM = 2] INTERVIEWER: USE THE [F9] KEY TO BACKUP TO THE SCREEN LABELED

AGE1 AND CORRECT THE RESPONDENT'S DATE OF BIRTH.
136

DKREFAGE [IF (CALCAGE IS 12 OR OLDER AND CONFIRM = DK/REF) OR AGE1 = DK/REF] For this study it is

very important that I collect your correct age so that you will be asked the right questions. Could you please

tell me your correct age?

AGE: [RANGE: 1 - 110]

DK/REF

IF DKREFAGE NOT (BLANK OR DK/REF) THEN CALCAGE = DKREFAGE

UNDER12b [IF DKREFAGE < 12] Since you are [CALCAGE] years old, we cannot interview you for this study. Thank you

for your cooperation. PROGRAM SHOULD ROUTE TO ENDAUDIO

LASTCHANCE [IF DKREFAGE = DK/REF] Since I am not certain what your age is, I cannot interview you for this

study. Thank you for your cooperation. PROGRAM SHOULD ROUTE TO ENDAUDIO

DEFINE CURNTAGE:

IF CALCAGE > 11 AND CONFIRM = 1, CURNTAGE = CALCAGE

IF CALCAGE > 11 AND CONFIRM = DK/REF AND DKREFAGE > 11, CURNTAGE = DKREFAGE

IF AGE1 = DK/REF AND DKREFAGE > 11, CURNTAGE = DKREFAGE

ELSE RESPONDENT IS INELIGIBLE; ROUTE TO ENDAUDIO

FIPE1 INTERVIEWER: WERE 2 PERSONS SELECTED FOR AN INTERVIEW AT THIS SDU?

1 YES

2 NO

FIPE2 [IF FIPE1 = 1 AND CURNTAGE = 18 OR OLDER] INTERVIEWER: WAS A 12 - 17 YEAR OLD CHILD

SELECTED FOR AN INTERVIEW AT THIS SDU?

1 YES

2 NO

FIPE3 [IF FIPE2 = 1 OR (FIPE1 = 1 AND CURNTAGE = 12 - 17)] INTERVIEWER: IS THIS RESPONDENT THE

PARENT OR LEGAL GUARDIAN OF THE 17 - 17 YEAR OLD CHILD WHO WAS SELECTED FOR AN

INTERVIEW? (VERIFY THIS WITH THE RESPONDENT IF YOU ARE UNSURE.)

1 YES

2 NO

NOTE: IF FIPE3 = 1, SET THE FLAG TO ADMINISTER THE PARENTING EXPERIENCES MODULE

DURING ACASI.

QD01 The first questions are for statistical purposes only, to help us analyze the results of the study. 

INTERVIEWER: RECORD RESPONDENT’S SEX.

1 MALE

2 FEMALE

DK/REF

QD03 Are you of Hispanic, Latino, or Spanish origin or descent?

1 YES

2 NO

DK/REF
137

QD04 [IF QD03 = 1] HAND R SHOWCARD 1. Which of these groups best describes you? Just give me the number or

numbers from the card.

TO SELECT MORE THAN ONE CATEGORY, PRESS THE SPACE BAR BETWEEN EACH CATEGORY YOU

SELECT.

1 MEXICAN / MEXICAN AMERICAN / MEXICANO / CHICANO

2 PUERTO RICAN

3 CENTRAL OR SOUTH AMERICAN

4 CUBAN / CUBAN AMERICAN

5 OTHER (SPECIFY)

DK/REF

QDO4OTHR [IF QD04 = 5] SPECIFY OTHER HISPANIC COUNTRY OR ORIGIN

 

DK/REF

QD05 HAND R SHOWCARD 2. Which of these groups describes you? Just give me the number or numbers from the card.

TO SELECT MORE THAN ONE CATEGORY, PRESS THE SPACE BAR BETWEEN EACH CATEGORY YOU

SELECT.

1 WHITE

2 BLACK / AFRICAN AMERICAN

3 AMERICAN INDIAN OR ALASKA NATIVE

4 NATIVE HAWAIIAN

5 OTHER PACIFIC ISLANDER

6 CHINESE

7 FILIPINO

8 JAPANESE

9 ASIAN INDIAN

10 KOREAN

11 VIETNAMESE

12 OTHER ASIAN

13 OTHER (SPECIFY)

DK/REF

QD05OTHR [IF QD05 = 13] SPECIFY OTHER RACIAL GROUP

 

DK/REF

DEFINE RACEFILL:

RACEFILL = RESPONSES GIVEN IN QD05 AND TEXT FROM QD05OTH IF APPLICABLE

Responses should appear in regular case and be separated by commas. The last response should be preceded

by the word “or.” For example, if a respondent selects categories 1, 3, and 6 in QD05, RACEFILL should

be: “White, American Indian or Alaskan Native, or Chinese”
138

QD06 [IF MORE THAN ONE RESPONSE SELECTED IN QD05] Which one of these groups, that is [RACEFILL], best

describes you?

SELECT ONLY ONE ANSWER.

1 WHITE

2 BLACK / AFRICAN AMERICAN

3 AMERICAN INDIAN OR ALASKA NATIVE

4 NATIVE HAWAIIAN

5 OTHER PACIFIC ISLANDER

6 CHINESE

7 FILIPINO

8 JAPANESE

9 ASIAN INDIAN

10 KOREAN

11 VIETNAMESE

12 OTHER ASIAN

13 IF QD05 = 13, FILL TEXT FROM QD05OTHR

IF QD05 NE 13 FILL WITH “OTHER (SPECIFY)”

DK/REF

[NOTE: ONLY CODES FOR RESPONSE CATEGORIES ENTERED IN QD05 WILL BE ACTIVE FOR

THIS QUESTION. IF THE INTERVIEW ENTERS AN INACTIVE RESPONSE CATEGORY, THE RANGE

ERROR BOX WITH APPEAR.]

QD07 [IF CURNTAGE = 15 OR OLDER] Which of the following best describes your current marital status? Are you

married, widowed, divorced or separated, or have you never married?

1 MARRIED

2 WIDOWED

3 DIVORCED OR SEPARATED

4 NEVER MARRIED

DK/REF

INTERVIEWER NOTE:

If the respondent is divorced but currently remarried, code as married. By “divorce” we

mean a legal cancellation or annulment of a marriage. By “separated” we mean legally

or informally separating due to marital discord.

QD08 [IF QDO7 = 1 OR 2 OR 3] How many times have you been married?

NUMBER OF TIMES: [RANGE: 1 - 9]

DK/REF

QD09 [IF CURNTAGE = 17 OR OLDER] Have you ever been in the United States’ armed forces?

1 YES

2 NO

DK/REF

QD10 [IF QD09 = 1 OR DK/REF] Are you currently on active duty in the armed forces, in a reserves component, or now

separated or retired from either reserves or active duty?

1 ON ACTIVE DUTY IN THE ARMED FORCES

2 IN A RESERVES COMPONENT

3 NOW SEPARATED OR RETIRED FROM EITHER RESERVES OR ACTIVE DUTY

DK/REF
139

MILTERM1 [IF QD10 = 1] I need to verify what I just entered into the computer. You said you are currently on active

duty in the armed forces. Is that correct?

1 YES

2 NO

DK/REF

MILCONT [IF MILTERM1 = 2 OR DK/REF] INTERVIEWER: USE THE [F9] KEY TO BACKUP TO THE SCREEN

LABELED QD10 AND CORRECT THE RESPONDENT’S CURRENT MILITARY STATUS.

MILTERM2 [IF MILTERM1 = 1] People who are currently on active duty in the armed forces are not eligible to be

interviewed in this study. I appreciate you taking the time to speak with me. Thank you.

PRESS [ENTER] TO CONTINUE.

[ROUTE TO ENDAUDIO]

QD11 HAND R SHOWCARD 3. What is the highest grade or year of school you have completed?

Please tell me the number from the card.

INCLUDE JUNIOR OR COMMUNITY COLLEGE ATTENDANCE; DO NOT INCLUDE TECHNICAL SCHOOLS

(BEAUTICIAN, MECHANIC, ETC.).

0 NEVER ATTENDED SCHOOL

1 1ST GRADE COMPLETED

2 2ND GRADE COMPLETED

3 3RD GRADE COMPLETED

4 4TH GRADE COMPLETED

5 5TH GRADE COMPLETED

6 6TH GRADE COMPLETED

7 7TH GRADE COMPLETED

8 8TH GRADE COMPLETED

9 9TH GRADE COMPLETED

10 10TH GRADE COMPLETED

11 11TH GRADE COMPLETED

12 12TH GRADE COMPLETED

13 COLLEGE OR UNIVERSITY / 1ST YEAR COMPLETED

14 COLLEGE OR UNIVERSITY / 2ND YEAR COMPLETED

15 COLLEGE OR UNIVERSITY / 3RD YEAR COMPLETED

16 COLLEGE OR UNIVERSITY / 4TH YEAR COMPLETED

17 COLLEGE OR UNIVERSITY / 5TH OR HIGHER YEAR COMPLETED

DK/REF

QD12 This question is about your overall health. Would you say your health in general is excellent, very good, good, fair, or

poor?

1 EXCELLENT

2 VERY GOOD

3 GOOD

4 FAIR

5 POOR

DK/REF
140

CALENDAR

CALND1 CALENDAR

Throughout the rest of this questionnaire, I will be asking you to answer a number of questions about three

specific time periods, namely the past 30 days, the past 12 months, and your lifetime. To help you remember

the first two time periods, let’s mark this calendar with the beginning dates for each one of them.

SHOW CALENDAR TO RESPONDENT.

Now let’s think about the past 30 days. According to the calendar, DATEFILL was 30 days ago, so I will

write DATEFILL here on the calendar. I’ll call that your 30-day reference date.

WRITE 30-DAY REFERENCE DATE ON CALENDAR AND CIRCLE DAY; UNDERLINE ENTIRE 30-

DAY PERIOD.

A number of questions will ask about the past 12 months, that is since this date last year. Let’s look at the

calendar and find that date — DATEFILL. I’ll call that your 12-month reference date.

WRITE 12 MONTH REFERENCE DATE ON CALENDAR AND CIRCLE DAY ON CALENDAR.

Please use this calendar as we go through the interview to help you remember when different things

happened. I will remind you to think about your 30-day reference date and your 12-month reference date

when I ask you questions.

PRESS [ENTER] TO CONTINUE.
141

Marijuana

MRJINTRO The next questions are about marijuana and hashish. Marijuana is also called pot or grass. Marijuana is

usually smoked, either in cigarettes, called joints, or in a pipe. It is sometimes cooked in food. Hashish is a

form of marijuana that is also called “hash.” It is usually smoked in a pipe. Another form of hashish is hash

oil.

MJ01. Have you ever, even once, used marijuana or hashish?

1 Yes

2 No ÷ COCINTRO

DK/REF ÷ COCINTRO

MJ02. How old were you the first time you used marijuana or hashish?

AGE: [RANGE 1 - 90]

DK/REF ÷ MJLAST3

DEFINE AGE1STMJ:

AGE1STMJ = MJ02

IF CURNTAGE < AGE1STMJ:

MJCC1 The computer recorded that you were [AGE1STMJ] when you first used marijuana or hashish. Is

this correct?

1 Yes

2 No ÷ MJCC4

DK/REF ÷ MJLAST3

MJCC2. The answers for the last question and an earlier question disagree. Which answer is correct?

1 I am currently [CURNTAGE] years old ÷ MJCC4

2 I was [AGE1STMJ] years old the first time

I used marijuana or hashish

3 Neither answer is correct

DK/REF ÷ MJLAST3

MJCC3. [IF MJCC2=2 OR MJCC2=3] Please answer this question again. What is your current age?

AGE: 

DK/REF ÷ MJLAST3

MJCC3a [IF MJCC3 < 12] Since you have indicated that you are [MJCC3] years old, we cannot

interview you for this study. Please tell your interviewer that you have finished the

survey. Thank you for your cooperation. PROGRAM SHOULD ROUTE TO

ENDAUDIO.

MJCC4. [IF MJCC2=1 OR MJCC2=3 OR MJCC1=2] Please answer this question again. Think about the

first time you used marijuana or hashish. How old were you the first time you used marijuana or

hashish?

AGE: [RANGE 1 - 90]

DK/REF ÷ MJLAST3

IF MJCC4 NOT(BLANK OR DK/REF) THEN AGE1STMJ = MJCC4

IF MJCC3 NOT(BLANK OR DK/REF) THEN CURNTAGE = MJCC3
142

IF AGE1STMJ = CURNTAGE OR AGE1STMJ <10:

MJCC5. The computer recorded that you were [AGE1STMJ] years old the first time you used marijuana or

hashish. Is this correct?

1 Yes ÷ MJ03a

2 No

DK/REF ÷ MJLAST3

MJCC6. [IF MJCC5=2] Please answer this question again. Think about the first time you used marijuana

or hashish. How old were you the first time you used marijuana or hashish?

AGE: [RANGE 1 - 90]

DK/REF ÷ MJLAST3

IF MJCC6 NOT(BLANK OR DK/REF) THEN AGE1STMJ = MJCC6

MJ03a [IF AGE1STMJ = CURNTAGE AND DATE OF INTERVIEW < DOB OR IF AGE1STMJ = CURNTAGE - 1 AND

DATE OF INTERVIEW $ DOB] Did you first use marijuana or hashish in [CURRENT YEAR - 1] or [CURRENT

YEAR]?

1 CURRENT YEAR - 1 (MJ03d)

2 CURRENT YEAR ( MJ03d)

DK/REF (MJLAST3)

MJ03b [IF AGE1STMJ = CURNTAGE - 1 AND DATE OF INTERVIEW < DOB] Did you first use marijuana or hashish in

[CURRENT YEAR - 2] OR [CURRENT YEAR - 1]?

1 CURRENT YEAR - 2 (MJ03d)

2 CURRENT YEAR - 1 (MJ03d)

DK/REF (MJLAST3) 

MJ03c IF AGE1STMJ = CURNTAGE AND DATE OF INTERVIEW $ DOB] In what month in [CURRENT YEAR] did

you first use marijuana or hashish? 

1 January

2 February

3 March

4 April

5 May

6 June

7 July

8 August

9 September

10 October

11 November

12 December

DK/REF (MJLAST3)

SKIP TO (MJLAST3)

[Note: Insert range check if MJ03c > current month].
143

MJ03d In what month in [YEAR FROM MJ03a or MJ03b] did you first use marijuana or hashish? 

1 January

2 February

3 March

4 April

5 May

6 June

7 July

8 August

9 September

10 October

11 November

12 December

DK/REF (MJLAST3)

MJLAST3. How long has it been since you last used marijuana or hashish?

1 Within the past 30 days -- that is, since DATEFILL

2 More than 30 days ago but within the past 12 months

3 More than 12 months ago ÷ COCINTRO

DK/REF ÷ COCINTRO

MJFRAME3. Now think about the past 12 months, from [FILL DATE] through today. We want to know how many days

you’ve used marijuana or hashish during the past 12 months. 

What would be the easiest way for you to tell us how many days you’ve used it?

1 Average number of days per week during the past 12 months ÷ MJWKAVE

2 Average number of days per month during the past 12 months ÷ MJMONAVE

3 Total number of days during the past 12 months

DK/REF ÷ MJYRAVE

MJYRAVE On how many days in the past 12 months did you use marijuana or hashish?

TOTAL # OF DAYS: [RANGE 1 - 366] ÷ MJ06

DK/REF ÷ MJMONAVE

MJMONAVE On average, how many days did you use marijuana or hashish each month during the past 12 months?

AVERAGE # OF DAYS PER MONTH: [RANGE 1 - 31] ÷ MJ06

DK/REF ÷ MJWKAVE

MJWKAVE. On average, how many days did you use marijuana or hashish each week during the past 12 months?

AVERAGE # OF DAYS PER WEEK: [RANGE 1 - 7] 

DK/REF ÷ MJ06

MJ06 [IF MJLAST3=1] Think specifically about the past 30 days, from [FILL DATE] up to and including today. During

the past 30 days, on how many days did you use marijuana or hashish?

NUMBER OF DAYS: [RANGE 0 - 30]

DK/REF ÷ COCINTRO
144

DEFINE TOTMJ:

IF MJYRAVE NOT(BLANK OR DK/REF) THEN TOTMJ = MJYRAVE

ELSE IF MJMONAVE NOT(BLANK OR DK/REF) THEN TOTMJ = MJMONAVE*12

ELSE IF MJWKAVE NOT (BLANK OR DK/REF) THEN TOTMJ = MJWKAVE*52

ELSE TOTMJ = DK/REF

IF TOTMJ = DK/REF, SKIP TO COCINTRO

IF TOTMJ NOT DK/REF AND MJ06 > TOTMJ:

MJCC7 For the last question, the computer recorded that you used marijuana or hashish on [MJ06 FILL]

of the past 30 days. Is this correct?

1 Yes 

2 No ÷ MJCC13

DK/REF ÷ COCINTRO

DEFINE FILLMJ:

IF MJYRAVE NOT (BLANK OR DK/REF), THEN FILLMJ = “[MJYRAVE] days”

ELSE IF MJMONAVE NOT (BLANK OR DK/REF), THEN FILLMJ = “[MJMONAVE] days per month”

ELSE IF MJWKAVE NOT (BLANK OR DK/REF), THEN FILLMJ = “[MJWKAVE] days per week”

DEFINE FILLMJA:

IF FILLMJ = “[MJMONAVE] days per month” OR “[MJWKAVE] days per week” FILLMJA = “for a total

of TOTMJ days”

ELSE FILLMJA = BLANK

MJCC8 The answers for the last question and an earlier question disagree. Which answer is correct?

1 I used marijuana or hashish on [FILLMJ] in the past 12 months [FILLMJA] 

2 I used marijuana or hashish on [MJ06] days in the past 30 days 

3 Neither answer is correct 

DK/REF ÷ COCINTRO

MJCC9 [IF MJCC8 = 2 OR MJCC8 = 3] Please answer this question again. Think about the past 12

months, from [FILL DATE] through today. We want to know how many days you’ve used

marijuana or hashish during the past 12 months. 

What would be the easiest way for you to tell us how many days you’ve used it?

1 Average number of days per week during the past 12 months ÷ SKIP TO

MJCC12

2 Average number of days per month during the past 12 months ÷ SKIP TO

MJCC11

3 Total number of days during the past 12 months

DK/REF ÷ COCINTRO

MJCC10 On how many days in the past 12 months did you use marijuana or hashish?

TOTAL # OF DAYS: [RANGE 1 - 366] ÷ MJCC12a

DK/REF ÷ MJCC12a

MJCC11 On average, how many days did you use marijuana or hashish each month during the past 12

months?

# OF DAYS/MONTH: [RANGE 1 - 31] ÷ MJCC12a

DK/REF ÷ MJCC12a

MJCC12 On average, how many days did you use marijuana or hashish each week during the past 12

months?

# OF DAYS PER WEEK: [RANGE 1 - 7] 

DK/REF ÷ MjcC12a
145

MJCC12a:

IF MJCC10 NOT(BLANK OR DK/REF) THEN TOTMJ = MJCC10

ELSE IF MJCC11 NOT(BLANK OR DK/REF) THEN TOTMJ = MJCC11*12

ELSE IF MJCC12 NOT(BLANK OR DK/REF) THEN TOTMJ = MJCC12*52

ELSE TOTMJ = DK/REF

IF MJCC8 = 2 SKIP TO COCINTRO

MJCC13 [IF MJCC7=2 OR MJCC8 = 1 OR MJCC8 = 3] Please answer this question again. Think

specifically about the past 30 days — that is, since [FILL DATE], up to and including today. 

During the past 30 days, on how many days did you use marijuana or hashish?

# OF DAYS: [RANGE 0 - 30]

0 ÷ COCINTRO

DK/REF ÷ COCINTRO 

IF MJ06 = 0:

MJCC14 The computer recorded that you used marijuana or hashish on 0 days during the past 30 days. Is

this correct?

1 Yes ÷ COCINTRO

2 No ÷ MJCC16

DK/REF ÷ COCINTRO

MJCC16 During the past 30 days, that is since [DATE FILL], on how many days did you use marijuana or

hashish?

# OF DAYS: [RANGE 0 - 30]

0 ÷ COCINTRO

DK/REF ÷ COCINTRO
146

2000 National Household Survey on Drug Abuse

Specifications for Programming

Items on Marijuana Abuse and Dependence

DRMJ [IF MAR12MON = 1 - 3] Think about your use of marijuana or hashish during the past 12 months as you answer

these next questions.

Press [ENTER] to continue.

DRMJ01[IF MAR12MON= 1 - 3] During the past 12 months, was there a month or more when you spent a lot of your time

getting or using marijuana or hashish?

1 Yes

2 No

DK/REF

DRMJ02[IF DRMJ01 = 2 OR DK/REF] During the past 12 months, was there a month or more when you spent a lot of your

time getting over the effects of the marijuana or hashish you used?

1 Yes

2 No

DK/REF

DRMJ04[IF MAR12MON= 1 - 3] During the past 12 months, did you try to set limits on how often or how much marijuana or

hashish you would use?

1 Yes

2 No

DK/REF

DRMJ05[IF DRMJ04 = 1] Were you able to keep to the limits you set, or did you often use marijuana or hashish more than

you intended to?

1 Usually kept to the limits set

2 Often used more than intended

DK/REF

DRMJ06[IF MAR12MON = 1 - 3] During the past 12 months, did you need to use more marijuana or hashish than you used

to in order to get the effect you wanted?

1 Yes

2 No

DK/REF

DRMJ07[IF DRMJ06=2 OR DK/REF] During the past 12 months, did you notice that using the same amount of marijuana or

hashish had less effect on you than it used to?

1 Yes

2 No

DK/REF

DRMJ08[IF MAR12MON= 1 - 3] During the past 12 months, did you want to or try to cut down or stop using marijuana or

hashish?

1 Yes

2 No

DK/REF
147

DRMJ09[IF DRMJ08 = 1] During the past 12 months, were you able to cut down or stop using marijuana or hashish every

time you wanted to or tried to?

1 Yes

2 No

DK/REF

DRMJ13[IF MAR12MON= 1 - 3] During the past 12 months, did you have any problems with your emotions, nerves, or mental

health that were probably caused or made worse by your use of marijuana or hashish?

1 Yes

2 No

DK/REF

DRMJ14[IF DRMJ13 = 1] Did you continue to use marijuana or hashish even though you thought it was causing you to have

problems with your emotions, nerves, or mental health?

1 Yes

2 No

DK/REF

DRMJ15[IF DRMJ13 = 2 OR DK/REF OR DRMJ14 = 2 OR DK/REF] During the past 12 months, did you have any physical

health problems that were probably caused or made worse by your use of marijuana or hashish?

1 Yes

2 No

DK/REF

DRMJ16[IF DRMJ15 = 1] Did you continue to use marijuana or hashish even though you thought it was causing you to have

physical problems?

1 Yes

2 No

DK/REF

DRMJ17[IF MAR12MON= 1 - 3] This question is about important activities such as working, going to school, taking care of

children, doing fun things such as hobbies and sports, and spending time with friends and family. 

During the past 12 months, did using marijuana or hashish cause you to give up or spend less time doing these types

of important activities?

1 Yes

2 No

DK/REF

DRMJ18[IF MAR12MON= 1 - 3] Sometimes people who use marijuana or hashish have serious problems at home, work or

school — such as:

- neglecting their children

- missing work or school

- doing a poor job at work or school

- losing a job or dropping out of school

During the past 12 months, did using marijuana or hashish cause you to have serious problems like this either at

home, work, or school?

1 Yes

2 No

DK/REF

DRMJ19[IF MAR12MON= 1 - 3] During the past 12 months, did you regularly use marijuana or hashish and then do

something where using marijuana or hashish might have put you in physical danger?
148

1 Yes

2 No

DK/REF

DRMJ20[IF MAR12MON= 1 - 3] During the past 12 months, did using marijuana or hashish cause you to do things that

repeatedly got you in trouble with the law?

1 Yes

2 No

DK/REF

DRMJ21[IF MAR12MON= 1 - 3] During the past 12 months, did you have any problems with family or friends that were

probably caused by your use of marijuana or hashish?

1 Yes

2 No

DK/REF

DRMJ22[IF DRMJ21 = 1] Did you continue to use marijuana or hashish even though you thought it caused problems with

family or friends?

1 Yes

2 No

DK/REF