Adult patients with obsessive-compulsive disorder and ADHD experienced earlier onset of and more severe obsessive-compulsive symptoms, according to a large cross-sectional study. “Recent findings suggest that OCD and ADHD could share common genetic predisposition factors or be associated with dysfunctions in similar neurotransmitter pathways,” Thiago BlancoVieira, PhD, from the department of psychiatry, Federal University of São Paulo, Brazil, and colleagues wrote.