many people react to alcohol different. if you only black out from drinking (which happens in people who drink too much at a time or maybe have an intolerance to it which causes it), then it's most likely not an alter/dissociative related. also, if you don't have other issues in general or other symptoms you notice outside of only when you drink, again, it's probably alcohol related.

it's a common effect of alcohol to cause memory issues as alcohol alters your perception as well as behavior. that is why for some people who are quiet without drinking, they might talk more when they drink. other people might become jerks or even violent and aggressive when they drink. people often do things out of character when under the influence of drugs or alcohol that they don't have memories of.

if alcohol is causing you problems, i'd suggest seeing a professional about it, esp. if you've been arrested.