A synthesis of the relationship of marijuana use with delinquent and problem behaviors

Marijuana use has been identified in both the popular and scientific literatures as a primary factor leading to later delinquent and problem behaviors. In this article we use meta-analytic techniques to summarize the findings from longitudinal research on this relationship and we delineate what these studies tell us about the magnitude of their longitudinal and cross-sectional relationships. Using multiple search strategies we identified 63 reports of 30 independent longitudinal studies from which we coded 511 effect-sizes. The cross-sectional findings measured early in adolescence are the strongest; these findings generally attenuate with age. For longitudinal relationships, stronger mean correlations are observed when delinquent and problem behaviors are measured first. The general strength and pattern of findings suggest that the nature of the relationship is likely to be one of co-morbidity and not cause and effect.