Interesting findings about the relationship between early substance use and troubled kids. It tries to answer whether substance use creates troubled kids or troubled kids engage in early substance use.
First, the prior consensus in child psychology and psychiatry has been that adolescents who go on to develop substance dependence are not normal adolescents who are experimenting with substances, but rather are highly likely to be adolescents with a prior history of conduct problems (Armstrong & Costello, 2002). If this is the case, the documented association between early substance exposure and adult outcomes would not be due to exposure per se, but instead would be the result of who is exposed (Wells, Horwood, & Fergusson, 2004). Prior research has not resulted in a consensus regarding the causal status of substance exposure (Agrawal, Neale, Prescott, & Kendler, 2004; Kandel, 2003; Lynskey et al., 2003; Prescott & Kendler, 1999). However, results from this study are consistent with a causal effect of early substance exposure among adolescents with no prior history of conduct problems. That is, early-exposed adolescents with no conduct-problem history, although they did not have an increased risk of failing to complete school, were more likely than their matched non-early-exposed counterparts to develop substance dependence, test positive for herpes, have an early pregnancy, and be convicted of criminal offenses.
Second, findings from this prospective study support a causal link between early substance exposure and a wide range of adult outcomes. Propensity-score-adjusted effects indicate that early substance exposure more than doubles the odds of adult substance dependence, herpes infection, early pregnancy, and criminal convictions.
Strangely, CADCA explains the study by describing some subjects as good kids and the others as bad kids.
[hat tip: Jess]