Next, we examined whether prior early substance use increases the likelihood of onset of SI and SA. In our data, evidence for this hypothesis was limited and most associations, which were with SA, were explained by comorbid factors, such as MDD, family history and externalizing disorders. Evidence that males with early substance use were less likely than females with early substance use to report SA is also consistent with the notion that early substance use in women might be indicative of a liability to both internalizing and externalizing problems (Brady et al., 1999; Kessler et al., 1997). Males with early substance use may be more likely to progress to other externalizing behaviors while females with early substance use may be vulnerable to future problems with depressed mood and suicidal thoughts as well (Kandel et al., 1991). Similarly, early substance use was less likely to be related to SI and SA in African-Americans relative to their European-American counterparts. Future studies with larger sample sizes for African-American participants might be better suited to the identification of aspects of substance use and misuse
