Why does drinking alcohol make some people mean?

'Filter' shut down: Alcohol anesthetizes some of the higher functions of the brain, including the one that 'filters' what we say and constrains what we do. This makes many less serious (the 'fun' / 'happy' drunks), but makes others brutally honest / 'mean' or downright angry. When sober, should address this pattern with your friend and discourage him/her from alcohol use due to its negative immediate effects on them.

Aggression & Alcohol: Loss of inhibitions, aggressive tendencies, personality trait.

IN VINO VERITAS: A Roman proverb. True personality can be revealed when intoxicated as the frontal lobes no longer provide any type of filter for actions or feelings that a person would otherwise hide. For some people repressed anger comes out. There is a similar Jewish saying from the Talmud that you can tell what a man is really like by how he handles his "kis" (money), "kos" (alcohol) and "ka'as" (anger)

Alcohol & Anger: People respond differently due to brain structure and function. Alcohol for some people cannot be metabolized properly, like some people have w/certain foods. If you, set limits to drinking, if another, please set limits w/them. Peace and good health.