Intra- and extra-familial influences on alcohol and drug misuse: a twin study of gene-environment correlation

Aims. Genotype-environment correlation refers to the extent to which indivi duals are exposed to environments as a function of their genetic propensiti es. These correlations are important in the study of psychopathology becaus e they identify environments that may maintain the expression of underlying genetic liabilities for a disorder. The present study examined the correla tion between genetic liabilities for alcohol and drug misuse with perceptio ns of the social environments of the family of origin and the classroom. De sign. Postal survey data were collected from monozygotic and dizygotic twin pairs. Setting. Twin pairs were recruited from Vancouver, British Columbia , Canada using newspaper advertisements and media stories. Participants. Ei ghty-five monozygotic and 77 dizygotic twin pairs were recruited from the g eneral population. Measurements, Twin pairs completed self-report measures of alcohol and drug misuse contained in the Dimensional Assessment of Perso nality Pathology, the Family Environment Scale, the Classroom Environment S cale, and the Traumatic Events Questionnaire. Findings. Genetically indexed alcohol and drug misuse scores were regressed on the environmentally index ed FES and CES scales. Genetic liabilities for alcohol and drug misuse were associated with decreased perceived family moral-religious emphases, famil y cohesion and classroom task orientation and increased perceptions of clas sroom order and organization (strictness), Conclusions. Genotype-environmen t correlations, in particular, moral-religious emphases in the home, appear to be important in the development of substance misuse.