Psychopharmacological violence may involve drug use by either the offender or the victim. Alcohol is the substance most studied in relation to violence. The economically compulsive model suggests that some drug users engage in crimes such as mugging to support their drug use. The systemic model focuses on the traditionally aggressive patterns of interaction within the system of drug distribution and use. Although many sources have emphasized the importance of the systemic model, little empirical evidence exists regarding this topic. However, systemic violence is undoubtedly a major contributor to total violence in the United States. It is a major killer and maimer of drug users and contributed to violent acquisitive crime in which nonusers are victimized. Some observers believe that drug-related violence is likely to increase and that recent immigration phenomena have contributed to the new violence. 64 reference notes