Sexual orientation and substance use trajectories in emerging adulthood.

AIMS The current study examined developmental changes in substance use behaviors (SUBS) based upon sexual orientation. The analyses also attempted to address a number of methodological limitations in the extant longitudinal literature (i.e. distinct operationalizations of sexual orientation, timing of sexual orientation assessment with respect to reports of SUBs, non-linear growth). PARTICIPANTS Data were drawn from a longitudinal study of incoming first-time college students at a large public university (n = 3720). DESIGN After a paper-and-pencil assessment just prior to matriculation, participants completed a web-based survey every fall and spring for 4 years (sub-sample n = 2854). FINDINGS Latent growth models revealed that sexual minorities demonstrated significant heterogeneity with regard to substance use trajectories. Initial levels and trajectories of the frequency of substance use for sexual minority individuals were distinct, generally, from their exclusively heterosexual peers. Methodologically, the timing of the assessment of sexual orientation influenced the results, and modeling non-linear components indicated that sexual minorities are at risk for exponential increases in their frequency of certain SUBs over time (i.e. drunkenness; cannabis use). CONCLUSIONS Sexual minority and majority individuals exhibited differences in SUBs during emerging adulthood, especially when using self-identification to define sexual orientation. Individuals who endorsed a sexual minority self-identification at the onset of emerging adulthood, as opposed to 4 years later, evidenced exponential increases in rates of drunkenness and cannabis use. These results support that the timing of assessment is important and that some trajectories of sexual minority SUBs are non-linear during this developmental period.