The following are excerpts from 2 papers describing the Family Study recruitment process and sample characteristics.

From: Miles, D. R., S., Stallings, M. C., Young, S. E., Hewitt, J. K., Crowley, T. J. & Fulker, D. W. (1998). A family history and direct interview study of the familial aggregation of substance abuse: the adolescent substance abuse study. Drug and Alcohol Dependence, 49, 105-114.

2.1. Sample description

This study sample comprises 100 matched treatment and control probands and their family members consecutively entering the ASA study. Treatment probands were male adolescents, 13-19 years old, referred by social service and juvenile justice agencies to an inpatient, residential treatment facility in the Denver Metro area for substance abuse (Riggs et aI., 1995; Young etaI., 1995; Thompson et al., 1996). Treatment probands were matched with a control adolescent only if theproband remained in treatment long enough to completethe assessment battery and at least one biological relative of the proband consented to participate in the study. Data was also obtained from all consenting first degree biological relatives and any other individual who had resided with the proband for at least 1 year. Individuals less than 11 years old were not interviewed. Genetic relatedness to the probands was determined by family report; no independent verifications (e.g. genotyping) was conducted. Control probands are male adolescents matched within 1 year of age, ethnicity and geographic location (zip code of residence) to the treatment probands. No other exclusionary criteria was applied to the control group adolescents. Recruitment of these adolescents and their families was carried out by a private research firm by randomly querying public phone lists within specified zipcodes. Thus, this control sample should be considered a volunteer community sample. All subjects were paid $20 for participation.

2.2. Subject attrition

The probands in this study were drawn from consecutive admissions to the treatment program. However, it should be noted that approximately 30% elope from the open facility prior to assessment and another 15% of the families refuse to participate. Although this may predict a bias towards health in our sample, 85% of treatment probands met DSM-III-R criteria for substance dependence, 100% met DSM-III-R criteria for substance abuse and 99% met DSM-III-R criteria for conduct disorder. Comparisons between the substance abusing probands that were dropped due to refusal of participation and pro bands that are included in the current sample do not show significant mean differences for age, nicotine dependence, alcohol dependence, drug dependence, or conduct disorder.

From Stallings, M.C., Corley, R.P., Hewitt, J.K., Krauter, K.S., Lessem, J.M., Mikulich, S.K., Rhee, S., Smolen, A., Young, S.E., Crowley, T.J. (2003). A genome-wide search for Quantitative Trait Loci influencing substance dependence vulnerability in adolescence. Drug and Alcohol Dependence, 70, 295-307.

2.1.1. Ascertainment of selected sibpair sample

Adolescent treatment probands were recruited from three treatment facilities (one residential and two outpatient facilities) in the Denver metropolitan area operated by the Division of Substance Dependence of the University of Colorado School of Medicine. The probands were 13-19 years of age (Mean: 15.9, Standard Deviation: 1.3) at time of assessment*/with most referred into treatment by social service and/or juvenile justice agencies for serious substance involvement and delinquency (ca. 1% are referred by parents or other sources). Proband participants were drawn from consecutive admissions to the treatment facilities between February 1993 and June 2001. Exclusionary criteria included imminent danger to self or others, current psychotic symptoms, or IQ scores B/80. Only probands with a biological full-sibling between the ages of 12 and 25 (ca. 60% of admissions) were utilized in the current study. The resulting selected sibpair sample included 250 proband-sibling pairs from 192 families (after omission of 24 individuals where paternity and/or full-sibling status was questioned based on genetic analysis). The self-reported ethnicity distribution of the 192 families was 7.8% African-American, 36.5% Hispanic, 52.1% Caucasian, and 3.6% other.