Capitalize it:
* When it's part of a proper noun:
* "He is in treatment at the National Institute on Alcohol Abuse and Alcoholism."
* "She read a book about Alcoholics Anonymous."
* When it's used as the name of a specific person or organization:
* "The Alcoholism foundation is hosting a fundraiser."
* "My friend, Alcoholism, has been sober for five years." (This is an unusual and potentially offensive use of the word).
Do not capitalize it:
* When it's used as a general term:
* "He is struggling with alcoholism."
* "The doctor diagnosed her with alcoholism."
In most cases, you will not capitalize "alcoholism."