Husbands and wives who frequently smoke cannabis are less likely to engage in domestic violence than those who consume the drug less regularly, a new study has suggested.
Researchers from Yale University, University of Buffalo and Rutgers followed 634 married couples for nine years.
They found that when couples used cannabis three times or more each month reported the lowest number domestic violence incidents (intimate partner violence) over the first nine years of marriage.
Intimate partner violence (IPV) was defined by the researchers as acts of physical aggressions, including hitting, beating and chocking.
The couples completed regular questionnaires throughout the study on how often they used the drug and other substances, such as alcohol.
They were also asked to report violence from their spouse within the last year, and any violent acts that had occurred during the year before marriage.
The study concluded that the more often both spouses smoked cannabis, the less likely they were to engage in domestic violence.
Lead researcher Kenneth Leonard, director of the UB Research Institute on Addictions, said the findings suggest cannabis use is predictive of lower levels of aggression towards a person's partner, but only over the course of a year.
“As in other survey studies of marijuana and partner violence, our study examines patterns of marijuana use and the occurrence of violence within a year period," he said. "It does not examine whether using marijuana on a given day reduces the likelihood of violence at that time.”
Mr Leonard noted other factors could be responsible for the link between husbands and wives who use cannabis and lower rates of domestic violence.
“It is possible, for example, that — similar to a drinking partnership — couples who use marijuana together may share similar values and social circles,” said Mr Leonard, “and it is this similarity that is responsible for reducing the likelihood of conflict.”
The authors suggested chronic cannabis users exhibit "blunted emotional reaction to threat stimuli" which could also reduce the likelihood of aggressive behaviour.
Mr Leonard is now hoping for further research examining day-to-day cannabis and alcohol use and the likelihood of domestic violence occurring on the same day before drawing stronger conclusions.
The study was published in the online edition of Psychology of Addictive Behaviors in August.