Developmental trajectories of marijuana use from adolescence to adulthood: relationship with using weapons including guns.

This is the first study to assess the associations between the trajectories of marijuana use and other predictors of violent behavior with the use of guns or other weapons as well as stealing without the use of weapons among inner-city African Americans and Puerto Ricans (N = 838). Logistic regression analyses examined whether the longitudinal trajectories of marijuana use compared with the trajectory of no/low marijuana use predicted violent behavior. A higher Bayesian posterior probability (BPP) for the increasing marijuana use trajectory group (AOR = 3.37, P < .001), the moderate use of marijuana trajectory group (AOR = 1.98, P < .01), and the quitter trajectory group (AOR = 1.70, P < .05) was associated with an increased likelihood of engaging in violence (i.e., shooting or hitting someone with a weapon) compared with the BPP of the no use of marijuana trajectory group. Our results address a number of important public health and clinical issues. Public health funds might be spent on prevention programs focused on decreasing the use of marijuana, increasing educational retention, and decreasing contact with deviant associates. Understanding the psychosocial conditions related to the use of weapons is critical for individuals involved in the criminal justice system, physicians, and other health care providers in managing individuals who engage in violent behavior.