Model used for estimation of genetic and environmental sources of variation in past-year drinking density, partialing age at drinking onset, stressful life events, and their interaction. Rectangles represent manifest variables, circles represent latent variables, triangle represents PYDD intercept. SLE, stressful life events; Onset14, drinking onset ≤14; Onset17, drinking onset ≤17; PYDD, past-year drinking density; Genetic, variation in PYDD because of additive genetic effects; Common Envt, variation in PYDD because of experiences shared by twins in a pair; Indiv Envt, variation in PYDD unique to 1 twin in a pair. The effects of demographic covariates (marital status, years of education, and family income) have been partialled from PYDD prior to model-fitting. Model was fit separately to data from male and female twin pairs.
