THE VIRGINIA TWIN-FAMILY STUDY OF ADOLESCENT BEHAVIORAL-DEVELOPMENT -ASSESSING SAMPLE BIASES IN DEMOGRAPHIC CORRELATES OF PSYCHOPATHOLOGY

The Virginia Twin-Family Study of Adolescent Behavioral Development (V TSABD) is a current longitudinal study of psychopathology in 1412 pair s of 8-16-year-old Caucasian twins and their parents. The primary aim of the study is to evaluate family-genetic and environmental risk fact ors for major domains of psychopathology in families representative of the Virginia Caucassian population. In this report, we utilize census -derived indices of neighbourhood income and urban residence to identi fy departures from population representation arising at the time of fa mily enrolment in the twin registry and family participation in a psyc hiatric interview. Furthermore, we consider whether demographic sample biases influenced prevalence rates of adult psychopathology (includin g major depression, generalized anxiety disorder, alcohol dependence, phobias, and panic disorder) in the VTSABD. Results indicated that fam ilies that enrolled in the twin registry (83% of those identified by V irginia schools) and that participated in the home interview (75% of t hose targeted) resided in urban and rural communities with a range of per capita income levels representative of the Virginia population. Ho wever, participation biases operated throughout the study and were pri marily characterized by losses of families living in low income, urban communities. There was also a smaller number of families living in hi gh income neighbourhoods that did not enrol in the twin registry or th at indefinitely postponed the psychiatric interview. These biases had small effects on prevalence rates of adult psychopathology in the VTSA BD sample, even though neighbourhood income was significantly related to a subset of adult diagnoses. We emphasize the usefulness of the cen sus methodology in evaluating sample biases in population-based psychi atric genetic studies.