People with family histories of alcoholism tend to have lower levels of endorphins- the endogenous morphine that is responsible for many of our pleasure responses- than do people genetically disinclined to alcoholism. Alcohol will slightly raise the endorphin level of people without the genetic basis for alcoholism; it will dramatically raise the endorphin level of people with that genetic basis. Specialists spend a lot of time formulating exotic hypotheses to account for substance abuse. Most experts point out, strong motivations for avoiding drugs; but there are also strong motivations for taking them. People who claim not to understand why anyone would get addicted to drugs are usually people who haven't tried them or who are genetically fairly invulnerable to them.
Andrew Solomon, The Noonday Demon: An Atlas of Depression
alcoholism, depression, disease