We propose that working with college populations is one way to address these challenges and obtain large numbers of individuals that can be readily phenotyped and followed longitudinally. Importantly, college students are entering a high risk age range for the onset of many psychiatric and substance use outcomes, which have peak onsets in the late teens and early 20 s. Data from the National Comorbidity Survey Replication sample indicate that three quarters of all lifetime cases of DSM-IV diagnoses start by age 24 (Kessler et al., 2005). Forty percent of cases of alcohol abuse have an age of onset (AO) between 16 and 21, and 40% of alcohol dependence cases manifest between ages 17 and 23. One quarter of generalized anxiety disorder cases have an onset by age 20, and one quarter of cases of major depression have an AO of 19. These findings come from a US population, but are consistent with WHO's World Mental Health data, which indicates that approximately three quarters of lifetime mental health disorders begin by the mid-20′s; many of these become evident between the mid-teen years and the mid-20′s (Kessler et al., 2007).
