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Research Article                                                                                                                                        Open Access

## Determinants of Binge Drinking among Adolescents in Denmark

Maria Pedersen 1,2* , Per Kragh Andersen 2 , Svend Sabroe 3

1 Department of Cardiology, Nephrology and Endocrinology, North Zealand Hospital, Hillerød, Denmark 2 Department of Public Health, University of Copenhagen, Denmark 3 Department of Public Health, Aarhus University, Denmark

*Corresponding author: sgplmariapedersen@gmail.com

## Abstract

Background and Objective: Binge drinking is a relatively common behavior among adolescents in Denmark. The aim of this  study  is  to  assess  whether  peer  alcohol  drinking,  mothers'  and  fathers'  attitudes  toward  alcohol  drinking,  and  the adolescents'  own  financial  situations  (e.g.,  the  presence  of  pocket  money)  predict  binge  drinking  among  adolescents  in Denmark.

Methods: This study is based on the Danish data from the European School Survey Project on Alcohol and Other Drugs, which took place in 2011. This cross-sectional survey obtained data from 2765 adolescents who were in grade 9 in Denmark at that time. Logistic regression was used to assess the association between the outcome variable of binge drinking and the exposure variables of alcohol-drinking peers, pocket money, and mother's/father's approval of intoxication.

Results: The risk of binge drinking increased with the number of alcohol-drinking peers (trend test, p < .0001) and with the amount of pocket money spent (trend test, p < .0001. The association between the mother's approval of intoxication and binge drinking is complex. Boys had a higher risk of binge drinking (odds ratio, 2.2 [1.1-4.3]) if their mothers approved of their intoxication with alcohol; however, this association was not seen among girls (odds ratio, 1.0 [0.5-2.0]). There was no significant association between the father's approval of intoxication and binge drinking.

Conclusion: The proportion of alcohol-drinking peers and the amount of pocket money spent appear to be determinants of adolescent binge drinking. The mother's approval of intoxication appears to be a determinant for binge drinking among boys but not among girls. The father's approval of intoxication does not appear to be a determinant of binge drinking.

Keywords: Adolescents, binge drinking, alcohol, peers, pocket money, parent's attitudes, determinants

## Introduction

Heavy alcohol drinking among adolescents is a large public  health  problem  in  Denmark.  In  general, Danish  adolescents  tend  to  drink  a  lot  of  alcohol, and only 7% of the Danish population never drinks alcohol (1).

Since 1995, substance use among Danish adolescents  has  been  monitored  every  fourth  year via the European School Survey Project on Alcohol and Other Drugs (ESPAD) (2), which also gathers data  from  adolescents  in  many  other  European countries.  Results  from  the  latest  ESPAD  survey demonstrated  that  Danish  adolescents  drink  more than  adolescents  anywhere  else  in  Europe,  with 77%  of  15-year-old  Danish  boys  and  75%  of  15year-old Danish girls reporting that they had drunk alcohol  during  the  month  before  the  survey.  The survey  also  showed  that  Danish  adolescents  drink large quantities of alcohol at a time: they were found to  have  imbibed  nearly  twice  as  much  alcohol during  their  last  drinking  sessions  (9.7  cl  of  pure alcohol/6.5 units) as compared with the average of all of the European  countries  (5.1 cl of pure alcohol/3.4 units).

In  Denmark,  it  is  forbidden  to  sell  alcoholic beverages  to  young  people  who  are  less  than  16 years old. The National Board of Health recommends  that  children  less  than  16  years  old drink no alcohol at all and that adolescents between the ages of 16 and 18 years not binge drink, which is defined  as  drinking  more  than  5  units  of  alcohol during one drinking  session.  These  recommendations are not followed by Danish adolescents, and this represents a large public health challenge. Heavy alcohol use can result in both short-term and long-term health risks, such as physical fights, unprotected  sex, problems  with  parents  or the police, and several different diseases later in life (24).

Previous research has reported sociodemographic variations with regard to alcohol use among adolescents,  including  gender  (5),  socioeconomic status  (6),  ethnicity  (7,  8),  and  family  patterns  (9, 10). Boys have a higher risk for drinking alcohol as compared  with  girls  (odds  ratio  [OR],  3.6;  95% confidence  interval  [CI],  2.9-4.1)  (5).  There  is  an association between ethnicity and alcohol drinking, and overall it has been shown that white adolescents tend  to  drink  more  often  than  black  or  Asian adolescents (7, 8). Previous studies have shown that adolescents  who  do  not  live  with  both  of  their parents have a higher risk of alcohol drinking (OR, 1.7;  95%  CI,  1.4-2.1)  and  higher  risk  of  binge drinking (OR, 1.4; 95% CI, 1.2-1.7) (9, 10). A study of Icelandic adolescents found  that adolescents have  a  higher  risk  of  drunkenness  if  their  parents have an indifferent attitude toward alcohol drinking among  their  children  (OR,  3.3;  95%  CI,  2.1-5.1) (11). Inconsistent findings have been reported with regard  to  socioeconomic  differences,  but  overall  it seems  that  high  parent  income  and  high  parent education have opposite effects on adolescent alcohol  drinking  (6).  Adolescents  whose  mothers have university degrees are less likely to binge drink than adolescents whose mothers have less education (OR, 0.8; 95% CI, 0.7-0.9). Among the adult Danish population,  alcohol  habits  are  also  influenced  by level  of  education:  adolescents  from  low-income families  have  a  lower  risk of  alcohol  drinking  than adolescents from middle-income families (OR, 0.8; 95% CI, 0.6-0.9). We did not find many studies of adolescents' personal financial situations as predictors  of  binge  drinking;  only  a  few  studies from the 1990s appear to have studied the association between  pocket money  and  alcohol drinking (12). More recent studies have shown that there is a positive association between pocket money  and  other  types  of  substance  use  such  as smoking, so it has been suggested that a reduction in pocket money can be used to prevent adolescent smoking (13, 14). It is thus likely that pocket money may play a significant role in the drinking of alcohol among adolescents.

Adolescents'  alcohol  drinking  most  often  takes place  at  social  gatherings  that  occur  on  weekends; this  is  in  contrast  with  the  drinking  patterns  of Danish  adults,  who  also  tend  to  drink  during  the week.  Adolescents  seldom  drink  when  they  are alone or not at a party or on their way to a party. Thus,  adolescents  who  spend  a  lot  of  time  with their  friends  at  parties  or  social  gatherings  tend  to drink  more  alcohol  (15).  Previous  research  has shown a strong association between binge drinking and  social  factors  such  as  the  impact  of  peers. Adolescents  who  have  many  friends  that  drink alcohol have  a higher risk of drinking alcohol themselves (OR, 29.0; 95% CI, 15.8-51.3); if all of their friends drink alcohol, they have a much higher risk of drinking alcohol themselves (OR, 59.6; 95% CI,  28.7-123.6)  (11).  These  findings  are  similar  to those obtained by studies conducted in the Netherlands, Sweden, and Portugal (16-18). However, it is not clear to what extent these results indicate social selection or peer socialization.

As  described  previously,  prior  research  has  tried to determine the factors associated with adolescent alcohol  drinking.  Peer  alcohol  drinking  has  been identified  as  a  determinant  of  adolescent  alcohol drinking  in  several other  countries; however,  it would  be  of  interest  to  determine  whether  peer alcohol  drinking  has  the  same  predictive  value  on Danish  adolescents,  because  Danish  adolescents' alcohol  habits  differ  from  those  of  adolescents  in many  of  the  other  countries.  In  Denmark,  binge drinking  is  much  more  common  than  it  is,  for example,  in  Iceland  and  Sweden,  where  only  13% and  31%,  respectively,  of  the  adolescents  reported binge  drinking  during  the month  before  they  were surveyed;  during  that  same  time  period,  56%  of Danish adolescents reported binge-drinking behavior  (2).  Therefore,  one  of  the  aims  of  the present  study  was  to  assess  whether  peer  alcohol drinking predicted adolescent binge drinking in Denmark.

In  Denmark,  adolescents  normally  live  at  home with their parents until the age of 18 years, so it is likely that parents influence adolescent alcohol drinking. However, alcohol drinking is a very widespread behavior in Denmark, with only 7% of all  Danes not consuming alcohol (1). The fact that nearly  all  Danish  adults  drink  alcohol  themselves may influence  their  attitudes  toward  and  influence on adolescent alcohol drinking. The second aim of this  study  is  to  assess  whether  parents'  attitudes toward alcohol drinking can predict adolescent binge drinking. Because it is not clear whether both parents  have  the  same  influence  on  adolescent behavior, mothers' and fathers' influences on adolescent binge drinking will be assessed separately.

As described previously, recent studies have shown  a  positive  association  between  the  use  of substances  like  cigarettes  and  the  availability  of pocket money. However, the role of pocket money as  a  predictor  of  binge  drinking  has  not  been  very well studied. Thus, it would be interesting to assess whether a larger amount of pocket money predicts adolescent  binge  drinking.  The  studying  of  this association will be the third aim of this research.

## Methods

## Study population

This  study  is  based  on  the  Danish  data  from ESPAD  2011.  ESPAD  is  a  cross-sectional  survey that  was  conducted  in  36  European  countries  in 2011. Data were collected from self-reported questionnaires that were handed out to ninth graders  in  randomly  selected  primary  and  private schools  in  Denmark.  Two  hundred  and  thirty-one schools were selected to participate in the ESPAD 2011  survey,  and  97  of  these  schools  (42%)  took part in the study. Ten percent of the students were not in school the day that the survey was conducted.  The  target  population  of  the  ESPAD study  was  restricted  to  students  born  in  1995  and who  were  15  years  old  at  the  time  of  the  survey. The  questionnaire  was  handed  out  to  students  in grade 9; however, in this grade level at the time of the study, there were also students who were born in  1994  (who were 16 years old at the time of the survey) as well as a few students born in 1993 and 1996. All of the Danish ninth graders who completed  the  survey  have  been  included  in  the analysis performed for the current study. The Danish part of ESPAD 2011 contains data regarding 2765 adolescents' drug and alcohol habits; 79.9% of the participants were 15 years old, 17.5% were 16 years old, 2.1% were 14 years old, and 0.5% were 17 years old at the time of the survey.

## Measurements

Three  exposure  variables  were  included:  1)  the proportion  of  drinking  peers;  2)  the  amount  of money spent without parent supervision; and 3) the attitudes of the mother and father toward adolescent  alcohol  drinking.  The  first  variable  was measured  by  asking  the  students,  'How  many  of your  friends  would  you  estimate  get  drunk?'  The answer options were 'None,'  'Few,' 'Some,' 'Most,' and 'All.' For the second variable, students  were  asked,  'How  much  money  do  you usually  spend  weekly  on  yourself  without  parent supervision?' Students then had the option to enter a four-digit number. The variable of pocket money was composed of both money given to the students by their parents and money earned by the adolescents  themselves.  The  attitudes  of  mothers and fathers toward adolescent alcohol drinking was measured  by  asking  the  students,  'What  do  you think  your  mother's/father's  reaction  would  be  if you get drunk?' The answer options were 'Would not  allow  it,'  'Would  discourage  it,'  'Would  not mind,' 'Would approve it,' and 'Do not know.'

The  outcome  variable  of binge drinking  was included.  This  variable  was  measured  by  asking students the following: 'Think back on the last 30 days. How many times (if any) have you had six or more  drinks  (1  drink  =  33  cl  with  5%  alcohol percent)  on  one  occasion?'  The  answer  options were 'None,' '1 time,' '2 times,' '3-5 times,' '6-9 times,'  and  '10  or  more  times.'  The  outcome variable  was  then  dichotomized  into  adolescents who have not been binge drinking and adolescents who  have  been  binge  drinking  between  1  and  10 times during the last month.

Ten variables were included as potential confounders:  1)  year  of  birth;  2)  gender;  3  and  4) mother's/father's education level; 5 and 6) mother's/father's attitude towards adolescent alcohol drinking; and 7 through 10) with whom the adolescent lives (mother,  father,  stepmother,  or stepfather). In every model, the potential confounders to be included were assessed by testing whether  the  potential  confounder  was  associated with the exposure variable and whether it could be a risk factor for the outcome  variable (data not shown).

The  questionnaire  as  a  whole  can  be  viewed elsewhere (2).

## Statistics

Logistic regression was used to assess the association  between  exposure  and  outcome.  Thus, the  associations  are  expressed  as  ORs  with  95% CIs. Tests for homogeneity, tests for trends across categories  of  the  exposure  variables,  and  tests  for interaction with age and gender for the association between exposure and outcome variables have been performed  (19).  For  the  association  between  the mother's and father's approval of drunkenness and binge drinking, data have been tested for interaction with  the  variables  of  living  with  the  mother  and living  with  the  father.  All  statistical  analyses  were made  with  the  use  of  SAS  9.2  software  (SAS Institute, Cary, NC).

Data have been collected via cluster sampling on the  class  level,  and  this  can  result  in  intra-class correlation.  The  models  have  been  analyzed  with and  without  adjustment  for  intra-class  correlation. Because the standard errors for log (OR) calculations  were  virtually  the  same  in  the  models, these have not been corrected for intra-class correlation in the results shown in this article.

## Ethical considerations

The ESPAD  survey followed Danish national ethical  rules  (2).  The  students  were  informed  that answering the questionnaire was voluntary.  No parental  consent  was  needed . Because  the  survey was  confidential  and  anonymous,  it  was  exempt from  approval  by  an  ethical  committee.  However, the  survey  was  approved  by  both  the  National Board of Health and the University of Aarhus.

## Results

Table 1 shows the sample characteristics distributed by gender. There are 18 missing values for gender, so  the  characteristics  of  only  2747  students  are shown; 48% of the students are boys, and 52% are girls.  Table  1  shows  that  the  majority  of  students were born in 1995 (75% boys and 84.5% girls) and that  63.5%  of  the  boys  and  55.9%  of  the  girls reported binge drinking during the previous month. In addition, 57.7% of the boys and 61% of the girls reported  that  the  majority  of  their  peers  drink alcohol,  12.2%  of  the  boys  and  5.8%  of  the  girls reported that their mothers did not mind adolescent drunkenness, and 49.5% of the boys and 44.9% of the  girls  reported  that  their  fathers  approved  of adolescent drunkenness.  The majority of these students spent between 100 and 249 DKK weekly without parental supervision (38.9% of the boys and 42.1% of the girls).

TABLE 1. Sample characteristics for boys and girls

|                                                         | Boys, N=1317   | Boys, N=1317   | Girls, N=1430   | Girls, N=1430   |
|---------------------------------------------------------|----------------|----------------|-----------------|-----------------|
|                                                         | %              | n              | %               | n               |
| Binge drinking (past 30 days)                           |                |                |                 |                 |
| 0 times                                                 | 36.5           | 454            | 44.1            | 585             |
| 1 time                                                  | 20.4           | 253            | 20.9            | 278             |
| 2 times                                                 | 16.7           | 207            | 15.1            | 200             |
| 3-5 times                                               | 17.4           | 217            | 13.0            | 173             |
| 6-9 times                                               | 5.3            | 66             | 4.9             | 65              |
| >10 times                                               | 3.7            | 46             | 2.0             | 27              |
| Missing                                                 |                | 74             |                 | 102             |
| Birth year                                              |                |                |                 |                 |
| 1993                                                    | 0.6            | 8              | 0.4             | 5               |
| 1994                                                    | 23.5           | 308            | 12.0            | 171             |
| 1995                                                    | 75.0           | 981            | 84.5            | 1203            |
| 1996                                                    | 0.9            | 12             | 3.1             | 44              |
| Missing                                                 |                | 8              |                 | 7               |
| Proportion of drinking peers                            |                |                |                 |                 |
| None                                                    | 2.3            | 30             | 2.5             | 36              |
| Few                                                     | 4.6            | 60             | 4.9             | 70              |
| Some                                                    | 23.3           | 303            | 22.3            | 317             |
| Most                                                    | 57.7           | 752            | 61.0            | 867             |
| All                                                     | 12.1           | 158            | 9.3             | 132             |
| Missing                                                 |                | 14             |                 | 8               |
| Mother's reaction on drunkenness                        |                |                |                 |                 |
| Would not allow                                         | 7.4            | 97             | 9.7             | 137             |
| Would discourage                                        | 29.5           | 385            | 33.7            | 476             |
| Would not mind                                          | 12.2           | 159            | 5.8             | 82              |
| Would approve                                           | 46.8           | 612            | 48.0            | 677             |
| Do not know                                             | 4.1            | 53             | 2.8             | 40              |
| Missing                                                 |                | 11             |                 | 18              |
| Father's reaction on drunkenness                        |                |                |                 |                 |
| Would not allow                                         | 8.5            | 110            | 10.7            | 152             |
| Would discourage                                        | 20.8           | 270            | 28.3            | 400             |
| Would not mind                                          | 15.3           | 198            | 10.4            | 147             |
| Would approve                                           | 49.5           | 643            | 44.9            | 635             |
| Do not know                                             | 5.9            | 77             | 5.7             | 80              |
| Missing                                                 |                | 19             |                 | 16              |
| Amount of weekly spent money without parent supervision |                |                |                 |                 |
| 0-49 DKK                                                | 19.0           | 234            | 14.2            | 192             |
| 50-99 DKK                                               | 17.0           | 209            | 18.5            | 250             |
| 100-249 DKK                                             | 38.9           | 480            | 42.1            | 568             |
| ≥250 DKK                                                | 25.1           | 310            | 25.2            | 340             |
| Missing                                                 |                | 84             |                 | 80              |

Note. 1 DKK = 0.13 EUR

All tests for interaction with age and gender for the association between exposure and outcome variables had results that were not significant, except  for  the  association  between  the  mother's attitude  toward  adolescent  alcohol  drinking  and adolescent binge drinking. For this association, there was a significant interaction with gender ( p = .05),  so  the  ORs  have  been  stratified  according  to gender.

For the association between the mother's and the father's reactions to drunkenness and binge drinking, there have been tests for interaction with the variables of living with mother and living with the father. Results for both tests were not significant,  so  the  effects  of  the  mother's  and  the father's  reactions  to  drunkenness  do  not  appear  to depend  on  whether  the  adolescent  lives  with  the mother or the father.

The  results  from  the  logistic  regression  analyses showed that adolescents who have a large proportion  of  peers  who  drink  alcohol  are  more likely to binge drink. Table 2 shows that the risk of binge drinking increases with the number of drinking  peers  (trend  test, p <  .0001).  If  all  of  the students'  friends  drink  alcohol,  the  student  has  a significantly  greater  risk  of  binge  drinking  (OR, 17.0; 95% CI, 6.8-42.7) as compared with students who do not have drinking peers.

TABLE 2 . Association between proportion of drinking peers and binge drinking at least once during the last month

| Proportion of peers who get drunk   | OR [95%CI]*    | OR [95%CI]**   | OR [95%CI]***   |
|-------------------------------------|----------------|----------------|-----------------|
| None                                | 1.0            | 1.0            | 1.0             |
| Few                                 | 1.1[0.5-2.7]   | 1.1[0.5-2.7]   | 1.4[0.5-3.7]    |
| Some                                | 2.7[1.3-5.7]   | 2.9[1.4-6.2]   | 3.5[1.5-8.3]    |
| Most                                | 6.8[3.2-14.3]  | 7.3[3.5-15.5]  | 7.0[3.0-16.6]   |
| All                                 | 18.6[8.3-41.4] | 19.6[8.7-43.8] | 17.0[6.8-42.7]  |
| Trend test                          | p<0.0001       | p<0.0001       | p<0.0001        |
| F(ν 4 )                             | p<0.0001       | p<0.0001       | p<0.0001        |

Note. OR = odds ratio; CI = confidence interval; F(ν 4 ) = 4 degree of freedom test *Unadjusted; **Adjusted for age and gender;***Adjusted for age, gender, mother's education, parents' attitude towards drunkenness, amount of money spent, living with father

Adolescents  who  manage  a  lot  of  pocket  money themselves  have  a  higher  risk  of  binge  drinking. Table  3  shows  that  the  risk  of  binge  drinking increases  with  the  amount  of  pocket  money  spent (trend  test, p <  .0001).  Adolescents  who  spend more  than  250  DKK  weekly  have  a  significantly higher risk of binge drinking (OR, 4.8; 95% CI, 3.66.5) as compared with students who spend 0 to 50 DKK weekly.

The association between the mother's approval of intoxication and binge drinking is complex. Table 4 shows  that  there  is  a  significant  association  with boys' binge drinking ( p = .0002); a similar association was not seen among girls ( p = .38). Boys have a higher risk of binge drinking (OR, 2.2; 95% CI, 1.1-4.3) if their mothers approve of them getting intoxicated by alcohol. This association is not seen among  girls;  if  their  mothers  approve  of  them getting  intoxicated  by  alcohol,  they  do  not  have  a higher risk of binge drinking (OR, 1.0; 95% CI, 0.51.9).

TABLE 3. Association between amount of money spent without parent supervision and binge drinking at least once during the last month

Amount of money

spent weekly

without parent

supervision

| 0-49 DKK    | 1.0          | 1.0          | 1.0          |
|-------------|--------------|--------------|--------------|
| 50-99 DKK   | 1.7[1.3-2.2] | 1.8[1.4-2.4] | 1.9[1.4-2.5] |
| 100-249 DKK | 2.7[2.2-3.5] | 2.9[2.3-3.7] | 2.6[2.0-3.4] |
| ≥250 DKK    | 5.4[4.1-7.2] | 5.9[4.4-7.7] | 4.8[3.6-6.5] |
| Trend test  | p<0.0001     | p<0.0001     | p<0.0001     |
| F(ν 3 )     | p<0.0001     | p<0.0001     | p<0.0001     |

Note. OR = odds ratio; CI = confidence interval; F(ν 3 ) = 3 degree of freedom *Unadjusted; **Adjusted for age and gender;***Adjusted for age, gender, parents' attitude towards drunkenness, living with father, proportion of drinking peers

TABLE 4 . Association between mother's reaction on adolescent drunkenness and binge drinking among girls and boys at least once during the last month

| Mother's reaction on drunkenness   | OR [95%CI]*   | OR [95%CI]**   | OR [95%CI]***   |
|------------------------------------|---------------|----------------|-----------------|
| Girls                              |               |                |                 |
| Would not allow                    | 1.0           | 1.0            | 1.0             |
| Would discourage                   | 0.8[0.5-1.4]  | 0.8[0.5-1.4]   | 0.7[0.4-1.4]    |
| Would not mind                     | 2.0[1.1-3.9]  | 2.0[1.1-3.8]   | 1.1[0.5-2.5]    |
| Would approve                      | 1.8[1.1-2.8]  | 1.8[1.1-2.8]   | 1.0[0.5-1.9]    |
| Do not know                        | 0.7[0.3-1.5]  | 0.7[0.3-1.5]   | 0.8[0.3-2.2]    |
| Trend test                         | p<0.0001      | p<0.0001       | p=0.14          |
| F(ν 4 )                            | p<0.0001      | p<0.0001       | p=0.38          |
| Boys                               |               |                |                 |
| Would not allow                    | 1.0           | 1.0            | 1.0             |
| Would discourage                   | 1.4[0.8-2.3]  | 1.4[0.8-2.3]   | 1.2[0.6-2.3]    |
| Would not mind                     | 2.2[1.2-3.9]  | 2.2[1.3-3.9]   | 1.1[0.5-2.3]    |
| Would approve                      | 3.7[2.2-6.1]  | 3.7[2.2-6.1]   | 2.2[1.1-4.3]    |
| Do not know                        | 0.7[0.3-1.4]  | 0.6[0.3-1.3]   | 0.4[0.2-1.2]    |
| Trend test                         | p<0.0001      | p<0.0001       | p=0.0006        |
| F(ν 4 )                            | p<0.0001      | p<0.0001       | p<0.0002        |

Note. OR = odds ratio; CI = confidence interval; F(ν 4 ) = 4 degree of freedom test *Unadjusted; **Adjusted for age and gender;***Adjusted for age, parents' education, proportion of drinking peers, father's attitude towards drunkenness, amount of money spent, living with father, stepfather or mother

The  association  between  the  father's  approval  of intoxication and binge drinking only demonstrated a significant  association  for  the  raw  association  ( p < .0001) and for the association adjusted for age and gender ( p < .0001). When the association was fully adjusted, there was no significant association found between  the  father's  approval  of  intoxication  and binge drinking ( p = .84). These findings are shown in Table 5.

OR [95%CI]*

OR [95%CI]**

OR [95%CI]***

TABLE 5 . Association between father's reaction on adolescent drunkenness and binge drinking at least once during the last month

| Father's reaction on drunkenness   | OR [95%CI]*     | OR [95%CI]**    | OR [95%CI]***   |
|------------------------------------|-----------------|-----------------|-----------------|
| Would not allow                    | 1.0             | 1.0             | 1.0             |
| Would discourage                   | 1.04[0.75-1.45] | 1.03[0.74-1.43] | 1.08[0.66-1.77] |
| Would not mind                     | 1.71[1.19-2.46] | 1.62[1.12-2.34] | 1.21[0.71-2.06] |
| Would approve                      | 2.31[1.69-3.15] | 2.23[1.63-3.06] | 1.27[0.76-2.11] |
| Do not know                        | 1.09[0.70-1.68] | 1.05[0.68-1.64] | 1.15[0.57-2.32] |
| Trend test                         | p <0.0001       | p <0.0001       | p=0.35          |
| F(ν 4 )                            | p <0.0001       | p <0.0001       | p=0.84          |

Note. OR = odds ratio; CI = confidence interval; F(ν 4 ) = 4 degree of freedom test *Unadjusted; **Adjusted for age and gender;***Adjusted for age, gender, parents' education, proportion of drinking peers, mother's attitude towards drunkenness, amount of money spent, living with father or stepfather

## Discussion

The  study  found  that  the  proportion  of  drinking peers appeared  to be a strong determinant of adolescent binge drinking and that the risk of binge drinking increased with an increasing proportion of drinking  peers.  These  findings  are  as  expected, because adolescent alcohol drinking is a social phenomenon. As described previously, several other studies from different countries have reported similar findings. A Dutch study found that adolescents  who  have  friends  that  drink  alcohol have  a  higher  risk  of  drinking  alcohol  themselves: there was nearly a five-fold higher risk for 12- to 15year-old boys and a seven-fold higher risk for 12- to 15-year-old  girls.  The  previous  studies  also  found that the risk is lower for older students between the ages  of  21  and  25  years;  in  this  group,  the  risk  is nearly two-fold for both men and women between the ages of 21 and 25 years (17). Thus, it seems that the  effect  of  peer  alcohol  drinking  decreases  with age. In this study, we found no interaction with age for  the  association  between  peer  alcohol  drinking and  the  risk  of  binge  drinking.  However,  the  age spread was not as wide as it had been in the other studies.

An Icelandic study  of  the  social  determinants  of adolescent drunkenness found a significant association between peer drunkenness and adolescent drunkenness ( p <  .0001) (11). Peer alcohol drinking seems to be an important determinant  of  adolescent  alcohol  drinking  across several countries. Countries like Iceland and Denmark  differ  significantly  with  regard  to  the prevalence of adolescent alcohol drinking: in Denmark,  76%  of  adolescents  reported  drinking alcohol  within  a  certain  30-day  period,  whereas during  that  same  period  only  17%  of  Icelandic adolescents reported drinking alcohol (2). Although these  two  countries  differ  significantly  with  regard to  the  prevalence  of  adolescent  alcohol  drinking, there seems to be a similar dose-response relationship between the amount of drinking peers and the risk of alcohol drinking. On the basis of the survey results and in conjunction with the results of other  surveys  from  Iceland  (11),  the  Netherlands (17),  Sweden  (18),  and  Portugal  (16),  it  could  be assumed that the determinant of drinking peers can be generalized to many other countries, despite the differences  in  their  cultures  with  regard  to  alcohol use.

The  study  also  found  that  a  large  amount  of pocket money is a determinant of adolescent binge drinking and that the risk of binge drinking increases with the amount of pocket money spent. We  have  not  been  able to find many  studies investigating the association between pocket money and  adolescent binge drinking;  however,  a  few studies from the 1990s found a positive association between  pocket  money  and  high  levels  of  weekly alcohol drinking (12, 20). It is quite surprising that there  are  so  few  studies,  because  there  has  been much  attention  given  to  the  association  between pocket money and other types of substance use like smoking.  A  study  of  Chinese  adolescents  showed that adolescents who receive more than 1000 RMB (120 Euro) each month have a six-fold higher risk of  smoking  as  compared  with  those  who  receive less  than  200  RMB  (24  Euro)  each  month  (14).  A study  from  India  showed  that  adolescents  who receive pocket  money  have  a  two-fold  risk  of smoking  (13).  These  findings  are  backed  up  by several other studies from Nepal (21), New Zealand (22), and the United States (23). The findings from the current study  show  that  there is a strong association  between  pocket  money  and  adolescent binge drinking in Denmark. This association needs to  be  studied  more  to  fully  understand  it  and  to clarify whether the association exists in other countries.

Several economic studies have shown that there is an association between the price of alcohol and the consumption of alcohol (24, 25). This study complements  this  knowledge  by  discovering  an association  between  the  amount  of  pocket  money spent  and  alcohol  consumption.  This  knowledge can  be  used  when  designing  preventive  alcohol policy,  because  adolescent  binge  drinking  can  be prevented from two economic angles: by increasing the  price  of  alcohol  and  by  advising  parents  and adolescents to keep the amount of self-administered pocket money at a low level.

This study found that mothers' approval of intoxication  appears  to  be  a  determinant  of  binge drinking  among  boys  but  not  among  girls.  Other studies  have  investigated  the  association  between parental  control  or  approval  of  intoxication  and alcohol  drinking,  and  they  have  reported  similar findings.  However,  none  of  these  studies  have found an interaction with gender for this association.  An  Icelandic  study  demonstrated  that adolescents  have  a  nearly  two-fold  higher  risk  of intoxication  if  their  parents  do  not  mind  alcohol drinking as compared with adolescents whose parents are against alcohol drinking (11). A French study  found  that  adolescents  with  a  low  grade  of parental  control  have  a  two-fold  higher  risk  of alcohol drinking as compared with adolescents with a  high  grade  of  parental  control (26). Parental control  and  approval  of  alcohol  intoxication  are associated with adolescent alcohol drinking. However,  this  study  found  that  mothers'  approval of  alcohol  intoxication  was  only  a  determinant  of binge drinking among the boys and not among the girls,  so  a  potential  interaction  with  gender  should be considered in similar studies.

Finally,  the  present  study  found  that  there  is  no significant association between the father's approval of intoxication and binge drinking when the association was adjusted for potential confounders. We have found no other  studies  that  support  this finding.  There  does  not  appear  to  be  a  logical explanation as to why the father has a less significant role in adolescent binge drinking as compared with the mother. In Denmark, there is a high  divorce  rate  of  40%  (27),  and  children  of divorced  parents  typically  live  with  their  mothers. However, the association has been adjusted for the variable of living with the father or a stepfather, so the living situation should not affect the association.

## Strengths

The  main  strengths  of  this study are that the analysis  has  been  made  on  a  large  dataset  that contains  data  about  2765  adolescents.  The  dataset also  allowed  for  adjustment  for  several  potential confounders.

## Limitations

There are some limitations to this study that should be  noted.  First,  the  study  design  is  cross-sectional and does not provide causal evidence. Because data about exposure and outcome were collected at the same  point  in  time,  the  outcome  can  affect  the information provided by the adolescents about exposure  variables.  Therefore,  it  is  possible  that adolescents with high levels of alcohol consumption state  that  their  friends  drink  more  alcohol  than adolescents with low levels of alcohol consumption or that adolescents who have-or who believe that they  have-peers  who  drink  a  lot  report  drinking more themselves than they actually do. If this is the case,  then  the  association  between  peer  alcohol drinking and binge drinking would be overestimated.  Second,  ESPAD  invited  randomly selected primary and private schools in Denmark to participate  in  the  study,  but  schools  for  students with  special  needs  as  well  as  adolescents  who  are not  attending  school  are  excluded  from  the  study. Therefore,  the  results  are  only  representative  of normal  adolescents  who  are  attending  primary  or private schools in Denmark. Third, ESPAD invited 231 schools to participate in the study, but only 97 schools  (42%)  participated.  The  low  participation rate is a general problem in Denmark, and it can be attributed to the high number of surveys carried out in  Danish  schools.  It  is  estimated  that  the  nonparticipating schools do not differ significantly from the  participating  schools  with  regard  to  drinking habits. Fourth, 10% of students were not in school the  day  that  the  survey  was  conducted.  These students  may  have  higher  alcohol  consumption levels  than  the  students  who  attended  school  that day, but this selection does not necessarily affect the associations.

## Clinical Significance

The  proportion  of  drinking  peers  and  the  amount of  pocket  money  spent  appear  to  be  important determinants  of adolescent binge drinking.  The mother's  approval  of  intoxication  appears  to  be  a determinant for binge drinking among boys but not among girls. This new knowledge helps to add some nuance  to  the  variety  of  determinants  of  binge drinking.  The  problem  of  binge  drinking  among adolescents may  need to be approached from several different angles, and many different aspects of  young  people's  lives  may  need  to  be  addressed. The solution  to  this  problem  may  need  to  include an economic  strategy (pocket money),  a social strategy  (peers),  and  a  parenting  strategy  (mother's disapproval of intoxication).

## Declaration of conflicting interests

None declared.

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