Chicago ? Almost one in five young American adults has a personality disorder that interferes with everyday life, and even more abuse alcohol or drugs, researchers reported Monday in the most extensive study of its kind.

The disorders include problems such as 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.

One expert said personality disorders may be overdiagnosed. But others said the results were not surprising since previous, less rigorous evidence has suggested mental problems are common on college campuses and elsewhere.

Experts praised the study’s scope — face-to-face interviews about numerous disorders with more than 5,000 young people ages 19 to 25 — and said it spotlights a problem college administrators need to address.

Study co-author Dr. Mark Olfson of Columbia University and New York State Psychiatric Institute called the widespread lack of treatment particularly worrisome. He said it should alert not only “students and parents, but also deans and people who run college mental health services about the need to extend access to treatment.”

Counting substance abuse, the study found that nearly half of young people surveyed have some sort of psychiatric condition, including students and nonstudents.

Personality disorders were the second most common problem behind drug or alcohol abuse as a single category. The disorders include obsessive, anti-social and paranoid behaviors that are not mere quirks but actually interfere with ordinary functioning.

The study was released Monday in Archives of General Psychiatry. It was funded with grants from the National Institutes of Health, the American Foundation for Suicide Prevention and the New York Psychiatric Institute.