ADHD, CD, and ODD: Systematic review of genetic and environmental risk factors.

This review aims to analyze the relationships between Attention-Deficit Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder (ODD), and Conduct Disorder (CD), particularly regarding the relative importance of genetic and environmental factors in the development of these disorders. Studies that examined at least two of these disorders were obtained from multiple databases, following the procedures of the Cochrane Collaboration initiative. Of the 279 documents obtained, nine were retained for in-depth analysis and were considered eligible for inclusion. In addition, eight studies from the manual search were included. The objectives, methodological aspects (sample and instruments), and the main conclusions were extracted from each study. Overall, the results suggest that (a) the causes for the onset and maintenance of these disorders are more associated with genetic factors than environmental factors, although the importance of the latter is recognized, and (b) children with ADHD have a predisposition to manifest behaviors that are common to ODD and CD, including the antisocial behavior that these children often display.