A seemingly obvious conclusion probably known for a generation — from Medical News Today:

After assessing couples’ first 9 years of marriage, the researchers found that husbands and wives who used marijuana frequently – two or three times per month or more – exhibited less frequent intimate partner violence (IPV) instigation by the husbands.

Anyone with any experience living knows alcohol is the weed killer. One odd characteristic of cannabis I’ve discovered over the years, at least for me, is to add alcohol with pot doesn’t make you any more stoned, but way-easily makes you way-more drunk.

(Illustration found here).

Although I’ve been alcohol-free for more than 19 years, memory has some shit stains that won’t come out, despite all the rubbing.
And any sane person knows the huge, most-ugly difference between alcohol and pot is aggressive violence. An old friend once noted that if you took two people out in the woods, and there encountered a deer, the stoner would want to feed it, the booze-hound would want to shoot it — extreme, admittedly, but the point…

And a main given and marijuana, from a piece on the stoner-couple study at the Washington Post:

The authors caution that while these findings are predictive — meaning couples who smoke are less likely to commit domestic violence — they don’t necessarily draw a causal line between the two behaviors.
Among the connections they hypothesize, “marijuana may increase positive affect, which in turn could reduce the likelihood of conflict and aggression.”
Translation: stoned people are happy, and happy people don’t fight.

All I can say is ‘Thank-you captain obvious.’