From “Seven Deadly Sins: The Biology of Being Human” by Guy Leschziner
Current data are inconclusive as to whether alcohol in and of itself is sufficient to cause violence, or simply increases the risk of it in susceptible individuals. However, in addition to the direct impact of intoxication on the frontal lobes, chronic alcohol dependency is associated with chemical changes in the amygdala, causing this region to be more excitable. This suggests that chronic alcohol abuse may directly induce brain changes that make people more prone to aggression, independent of acute intoxication.