The National Institute on Alcohol Abuse and Alcoholism (NIAAA), a federal agency that researches and educates the public about alcohol use, defines moderate alcohol consumption as up to two standard drinks per day for men and one for women and older people, amounts that are not considered physically harmful. Addiction expert Margaret O. Hyde explains that the vast majority of people who drink are able to limit their alcohol intake to these safe levels:

For most people, alcohol is not addictive and may never be a problem. In moderate amounts, the indirect effect of alcohol on the body is usually one of stimulation that produces a mood of emotional freedom. Most people who drink do so in a responsible manner by carefully choosing the time, place, and amount.

But some people are unable to limit or control their drinking.

Once...