DOI: 10.3886/icpsr27022.v2
title: National Longitudinal Study of Adolescent Health (Add Health), 1994-2008: Friend Files [Restricted Use]
title: Version 2

description: The National Longitudinal Study of Adolescent Health (Add Health) is a longitudinal study of a nationally representative sample of adolescents in grades 7-12 in the United States during the 1994-95 school year. The Add Health cohort has been followed into young adulthood with four in-home interviews, the most recent in 2008, when the sample was aged 24-32. Add Health combines longitudinal survey data on respondents' social, economic, psychological, and physical well-being with contextual data on the family, neighborhood, community, school, friendships, peer groups, and romantic relationships, providing unique opportunities to study how social environments and behaviors in adolescence are linked to health and achievement outcomes in young adulthood. The fourth wave of interviews expanded the collection of biological data in Add Health to understand the social, behavioral, and biological linkages in health trajectories as the Add Health cohort ages through adulthood. The files contained in this component of the Add Health restricted data are the Wave I, Wave II In-Home Friendship and In- School Friendship Nominations files, and the Wave III Friend ID Numbers. For more information, please see the study website.
description: Weight variables for Wave I (21600-0001) are in a separate data file: 21600-0002. Weights for Wave II are included in the Wave I weight data file: 21600-0002. Wave III weights are in a separate data file: 21600-0013. Education data weights are in 21600-0016 and 21600-0017.
description: ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection: Performed consistency checks.; Standardized missing values.; Checked for undocumented or out-of-range codes..
description: Datasets: 
 
 DS0: Study-Level Files 
 DS1: Wave I In-Home Friendship Nominations Data 
 DS2: Wave II In-Home Friendship Nominations Data 
 DS3: Wave I In-School Friendship Nominations Data 
 DS4: Wave III Friends Data
description: audio computer-assisted self interview (ACASI), record abstracts, computer-assisted personal interview (CAPI), computer-assisted self interview (CASI), computer-assisted telephone interview (CATI), coded on-site observation, cognitive assessment test, face-to-face interview, paper and pencil interview (PAPI), self-enumerated questionnaire, on-site questionnaire, telephone interview 
2014-06-30 This study has been deaccessioned and is no longer distributed by ICPSR or DSDR.
 Wave I and Wave II field work was conducted by the National Opinion Research Center of the University of Chicago. Wave III field work was conducted by the Research Triangle Institute.
description: Adolescents in grades 7-12 and their families.
description: Wave I, Stage 1 School sample: stratified, random sample of all high schools in the United States. A school was eligible for the sample if it included an 11th grade and had a minimum enrollment of 30 students. A feeder school, a school that sent graduates to the high school and that included a 7th grade, was also recruited from the community. Wave I, Stage 2: An in-home sample of 27,000 adolescents was drawn consisting of a core sample from each community plus selected special over samples. Eligibility for over samples was determined by an adolescent's responses on the In-School Questionnaire. Adolescents could qualify for more than one sample. In addition, parents were asked to complete a questionnaire about family and relationships. The Wave II in-home interview sample is the same as the Wave I in-home interview sample, with a few exceptions. Information about neighborhoods/communities was gathered from a variety of previously published databases. Wave III: The in-home Wave III sample consists of Wave I respondents who could be located and re-interviewed six years later. Wave III also collected High School Transcript Release Forms as well as samples of urine and saliva.