This study uses public-use data from the National Longitudinal Study of Adolescent to Adult Health (Add Health; Harris et al., 2009). Add Health is a nationally representative, longitudinal study of adolescents that focused on how behaviors and social environments during adolescence are linked to adult outcomes (Harris, 2011). Wave I of Add Health was conducted as in-school and in-home interviews while participants were in the 7th - 12th grades (1994-1995). Three follow-up surveys were conducted: Wave II during 1995-1996 (participants in the 12th grade during Wave I were excluded); Wave III during 2001-2002; and Wave IV during 2007-2008. Individuals who provided substance use and depressive symptoms data during at least one Add Health wave were eligible for inclusion in our analysis. We restricted our sample to measurement occasions at which individuals were ages 12 to 31, due to data sparseness outside of this age range. Of the original 6,504 individuals in the public use data, our sample included 6,070 individuals (93%) and 19,893 measurement occasions (an average of 3.3 per individual). Fifty one percent (51%) of individuals were female; 70% identified as White, 19% identified as Black, and 11% as other race; 12% were of Hispanic ethnicity.
