(Our happy hour fact to amaze your drinking buddies with.)

About 20 percent of young American adults have a personality disorder which interferes with everyday life, and close to a quarter of the rest abuse drugs or alcohol.

These figures come from more than 5,000 face-to-face interviews with 19-25 year olds -- the most extensive study of its kind. After drug and alcohol abuse, the most prevalent condition was obsessive-compulsive disorder, which popped up in 8 percent of those surveyed. Antisocial and paranoid behaviors also ranked high.

While the study's authors warn of a need for more mental health services to deal with those who aren't currently getting help, other experts cautioned that personality disorders are being overdiagnosed.

What is certain is that once half of the population is diagnosed with a psychiatric condition, there needs to be a new word to describe "normal." We nominate "boring."

Click here to have Happy Hour Hero delivered to your desktop every pour time.

The new Happy Hour Hero widget brings amazing facts and figures to your desktop, MySpace page, Facebook profile, or blog: