Psychiatric comorbidity in children and adolescents with reading disability.

This study investigated the association between reading disability (RD) and internalizing and externalizing psychopathology in a large community sample of twins with (N = 209) and without RD (N = 192). The primary goals were to clarify the relation between RD and comorbid psychopathology, to test for gender differences in the behavioral correlates of RD, and to test if common familial influences contributed to the association between RD and other disorders. Results indicated that individuals with RD exhibited significantly higher rates of all internalizing and externalizing disorders than individuals without RD. However, logistic regression analyses indicated that RD was not significantly associated with symptoms of aggression, delinquency, oppositional defiant disorder, or conduct disorder after controlling for the significant relation between RD and ADHD. In contrast, relations between RD and symptoms of anxiety and depression remained significant even after controlling for comorbid ADHD, suggesting that internalizing difficulties may be specifically associated with RD. Analyses of gender differences indicated that the significant relation between RD and internalizing symptoms was largely restricted to girls, whereas the association between RD and externalizing psychopathology was stronger for boys. Finally, preliminary etiological analyses suggested that common familial factors predispose both probands with RD and their non-RD siblings to exhibit externalizing behaviors, whereas elevations of internalizing symptomatology are restricted to individuals with RD.