Alcohol use is more likely than marijuana use to lead to violence between partners, according to studies done at the University of Tennessee, Knoxville.
Research among college students found that men under the influence of alcohol are more likely to perpetrate physical, psychological or sexual aggression against their partners than men under the influence of marijuana. Women, on the other hand, were more likely to be physically and psychologically aggressive under the influence of alcohol but, unlike men, they were also more likely to be psychologically aggressive under the influence of marijuana.
The research has implications for domestic violence intervention and prevention programs.
The studies were conducted by Ryan Shorey, a psychology doctoral student; Gregory Stuart, a psychology professor; Todd Moore, an associate psychology professor; and James McNulty, an associate professor of social psychology at Florida State University. The study of male participants is published in the journal Addictive Behaviors and the study of female participants is published in the journal Psychology of Addictive Behaviors.
The researchers' goal was to find correlations between alcohol and marijuana use and the potential for physical, psychological and sexual violence against partners. The studies are among the first to investigate the timing of alcohol and marijuana use and intimate partner violence in college students.
Two studies included male and female college students who were at least 18 years old, had been a relationship for at least a month that involved two days a week of face-to-face contact, and had consumed alcohol in the previous month. The subjects completed an online diary once a day for 90 days.
The study of men found that odds of psychological, physical and sexual violence increased with subsequent use of alcohol. Specifically, odds of physical and sexual abuse increased on days where any alcohol was consumed and with each drink consumed. Odds of psychological abuse increased only on days when five or more drinks were consumed.
Marijuana use was unrelated to violence between intimate partners.
The study of college women found that alcohol use increased the odds of physical and psychological aggression while marijuana use increased the odds of psychological aggression.
"I think it is too early to make definitive conclusions regarding the role of marijuana and intimate partner violence perpetration, as the research in this area is quite young and, to date, studies have provided conflicting evidence regarding its role in increasing the odds for violence," said Stuart. "However, we now have numerous studies suggesting alcohol use does increase the odds for violence between partners."
Another study by the authors and psychology doctoral student Sara Elkins looked at women arrested for domestic violence. This study, published in the Journal of Consulting and Clinical Psychology, found that when women used marijuana they were less likely to perpetrate physical violence.
The authors say their findings provide further support for the numerous negative consequences associated with heavy alcohol consumption, particularly among college students.
"Our findings suggest that dating violence prevention and intervention programs should target reduction in alcohol use, but surprisingly, most of these programs largely ignore alcohol use," said Shorey.
Stuart noted that their other research has shown that men arrested for domestic violence in batterer intervention programs received short-term benefits when they were given a 90-minute treatment addressing their alcohol problems.
According to the authors, more research on the relationship between marijuana use and violence is needed prior to making any suggestions related to domestic violence intervention and prevention programs.