Once it starts rolling, it gathers. A small exchange becomes a shouting match becomes something with consequences, and every step feels reasonable given the one before.

What the research says

In a laboratory study of 69 couples, aggression was highest when three things came together: heavy dwelling on the provocation, little reappraisal, and alcohol. The factors combined rather than acting alone. A separate experiment found that people who had just been drained by a self-control task drank more alcohol when given free access, which is one way an evening compounds on itself. Both are laboratory settings, so the pattern travels better than the numbers.

Strength of evidence: one line of research. A single study, or a theoretical account.