Brew BK, et al. - The existence and nature of familial aggregation for the comorbidity of atopic diseases and depression or anxiety was inquired among the participants from the Childhood and Adolescent Twin Study in Sweden (CATSS), using validated questionnaires. Parental education, recent maternal psychological stress, childhood family trauma and parental country of birth, representing familial liability candidates, were also tested. In families, a tendency for a comorbid occurrence of atopic diseases and depression or anxiety was noted. Considering comorbidity in both the individual and the individual's siblings was recommended when treating for 1 disease. No evidence supported a genetic explanation for comorbidity.