THE INFLUENCE OF SPOUSES BEHAVIOR AND MARITAL DISSOLUTION ON MARIJUANA USE - CAUSATION OR SELECTION

Similarity between spouses may result from prior similarity (selection ) or interpersonal influence (causation) or both. We investigate spous es' mutual influences on marijuana use in a two-wave longitudinal coho rt of 490 married pairs, ruing data obtained twice from each spouse ov er a 5 1/2 year interval. To estimate processes during marriage free o f sample selection bias, we also include marriages that dissolved duri ng the interval, and we analyze the impact of divorce on the drug use of the spouse who was reinterviewed. We test hypotheses to disentangle causation effects of spouse (or event) from selection effects involve d in assortative mating (or divorce), using models with and without co ntrols for latent individual propensities to use marijuana. We find th at marital selection effects predominate over causation effects and th at divorce affects spouses' continued marijuana use. We discuss the im plications of the findings for understanding the persistence of drug u se in adulthood, gender differences in the relationship of substance u se with marriage and divorce, and the study of interpersonal influence s.