Objective: To investigate meta-analytically if the association between ADHD and illicit substance use (ISU) is maintained when controlling for conduct disorder/oppositional-defiant disorder (CD/ODD).
Method: A systematic literature review was conducted through Medline from 1980 to 2008. Data extracted and selections made by one author were reviewed by another.
Results: Fifteen articles presented odds ratios (ORs) for the development of ISU in individuals with ADHD controlling for CD/ODD. In total, the study covered results for more than 1,000 individuals. The combined OR for studies that included in their analysis exclusively ISU was 1.35 (0.90-2.03), p = .15, heterogeneity = 55%. Lack of control for socioeconomic status was related with a weaker association between ADHD and ISU.
Conclusion: The existing data do not indicate that ADHD increases the risk of ISU beyond the effects of CD/ODD. However, the combination of all existing data is limited in power to detect a small increase in chance.
Keywords: ADHD; comorbidity; conduct disorder; drug; substance.