Past research has indicated that couples who abuse substances are at a greater risk for divorce, in part because substance abuse often leads to an increase in domestic violence.

However, new research has found that when it comes to marijuana use, the opposite effect occurs: couples who frequently use marijuana are actually at a lower risk of partner violence.

Researchers from Yale University, University of Buffalo and Rutgers recruited 634 couples from 1996 to 1999 while they were applying for a marriage license in New York State. After an initial interview, the researchers followed the couples over the course of nine years using mail-in surveys to measure the effects of marijuana use on intimate partner violence (IPV).

The study defines IPV as acts of physical aggression, such as slapping, hitting, beating and choking, and it was measured by asking couples to report violence committed by them or toward them in the last year.

At the end of the first year, 37.1 percent of husbands had committed acts of domestic violence.

Marijuana use was measured by asking participants how often they used marijuana or hashish (defined as pot, […]