CHICAGO (AP) -- Researchers say almost one in five young American adults has a personality disorder that interferes with everyday life, and even more abuse alcohol or drugs.

Add those in, and it's about half the 15-to-25 age group.

The disorders include obsessive or compulsive tendencies and anti-social behavior that can sometimes lead to violence.

The study also found that fewer than 25 percent of college-aged Americans with mental problems get treatment.

Study co-author Dr. Mark Olfson says he's concerned about the widespread lack of treatment.

The study, appearing in Archives of General Psychiatry, was based on interviews with more than 5,000 young adults in 2001 and 2002.

(Copyright ©2008 by The Associated Press. All Rights Reserved.)