Importantly, conduct disorder is observed in approximately 30% to 50% of adolescents with ADHD (Biederman et al. 1991). Several prospective studies have found that the relation between ADHD and SUD is no longer significant after controlling for conduct disorder (Barkley et al. 2004; August et al. 2006). However, Elkins et al. (2007) showed that ADHD was a significant prospective predictor of SUD even after taking into account a diagnosis of conduct disorder. Furthermore, population-based studies indicate that conduct disorder and oppositional defiant disorder increase the likelihood of developing a SUD (Nock et al. 2006, 2007). Ohannessian et al. (1995) found that conduct disorder during childhood and antisocial behavior during adulthood are among the most powerful predictors of adult SUD compared to other psychiatric disorders.
