THE VIRGINIA TWIN STUDY OF ADOLESCENT BEHAVIORAL-DEVELOPMENT - INFLUENCES OF AGE, SEX, AND IMPAIRMENT ON RATES OF DISORDER

Background: The Virginia Twin Study of Adolescent Behavioral Developme nt is a cohort-longitudinal epidemiological study that uses the geneti c twin design to study the development and maintenance of child psychi atric disorders. We determined the rates of DSM-III-R disorders, disor ders with impairment, and age, sex, and comorbidity effects. Methods: Families of 2762 white twins aged 8 to 16 years participated. Twins an d their parents were asked systematically about risk factors and curre nt psychiatric symptoms by means of investigator-based psychiatric int erviews and questionnaires. The DSM-III-R diagnoses were made for majo r depressive disorder, separation anxiety, overanxious disorder, simpl e phobia, social phobia, agoraphobia, oppositional defiant disorder, c onduct disorder, and attention deficit hyperactivity disorder. Results : The 3-month point prevalence for any DSM-III-R disorders was 413 per 1000, and that for disorders with associated impairment was 142 per 1 000. Emotional disorders with impairment occurred in 89 per 1000, with girls being more commonly affected; behavioral disorders had a preval ence of 71 per 1000, with boys being more frequently affected. The pro portion with disorder who also had functional impairment varied across disorders; anxiety and phobic disorders were particularly likely not to be accompanied by impairment. Rates of emotional and behavioral dis orders increased over the age range. There was extensive comorbidity a mong disorders. Conclusions: The prevalence rates and patterns of find ings from this study of twins are consistent with those of other epide miological studies, supporting previous findings of few differences in rates of psychiatric disorder between twins and singletons. The impor tance of including measures of functional impairment is evident by its effect on rates of disorder and patterns of comorbidity.