Illicit Drug Use, Cigarette Smoking, and Eating Disorder Symptoms: Associations in an Adolescent Twin Sample

Objective: Twin studies have shown that genetic factors in part explain the established relation between alcohol use (i.e., problematic use or abuse/dependence) and eating disorder symptoms in adolescent and adult females. However, studies have yet to elucidate if there are similar shared genetic factors between other aspects of substance involvement, such as illicit drug use and repeated cigarette smoking. Method: For those sex-specific phenotypic correlations above our threshold of.20, we used a behavioral genetic design to examine potential shared genetic overlap between self-reported lifetime illicit drug use and repeated cigarette smoking and the eating disorder symptoms of drive for thinness (DT), bulimia (BU), and body dissatisfaction (BD), as assessed with the Eating Disorder Inventory-II in 16- to 17-year-old female and male twin pairs. Results: Only phenotypic correlations with illicit drug use met our threshold for twin modeling. Small to moderate genetic correlations were observed between illicit drug use and BU in both girls and boys and between illicit drug use and in girls. Conclusions: Similar etiological factors are at play in the overlap between illicit drug use and certain eating disorder symptoms in girls and boys during adolescence, such that genetic factors are important for covariance. Specifically, illicit drug use was associated with bulimia nervosa symptoms in girls and boys, which parallels previous substance use research finding a genetic overlap between alcohol use and bulimia nervosa symptoms. Future research should prospectively examine developmental trajectories to further understand the etiological overlap between substance involvement and eating disorder symptoms.