Moody or Mentally Ill?

John Hill was a typical teenager in many ways: He started smoking when he was in high school, which upset his mother, and he spent a lot of time in his room alone, staying up until 5 in the morning playing video games. He went to school but often signed himself out sick after a couple of hours, and his grades plummeted.

When his mother asked what was wrong, he told her to leave him alone.

John's mother Barbara, of Homedale, Idaho, was worried. But, she said, "He had always been the kid who never got in trouble … I kind of assumed it was just adolescent behavior kicking in."

Teenagers are, by definition, difficult. Like the stereotype, they can be moody, reckless and emotionally volatile, crying in the shower, screaming at their parents, slamming their bedroom doors behind them.

It's not a new phenomenon: the psychologist G. Stanley Hall dubbed the teen years a time of "storm and stress" more than 100 years ago. But experts now know these years are a critical period of development when serious mental illnesses can emerge and progress undetected and untreated, in part because they are perceived as typical teen behavior and may manifest with symptoms different from those in adults.

By the time they are college age, nearly one in five young American adults has a personality disorder that interferes with everyday life, found an extensive study released Monday by Columbia University and the New York State Psychiatric Institute.

While half of all serious adult psychiatric illnesses start before the age of 14, evidence suggests that parents may be the last to know. One study found that parents were unaware of 90 percent of suicide attempts made by teenagers. Another report from a screening program found that the vast majority of parents of kids identified as having psychiatric symptoms thought their child was all right.

"The tendency of parents is to think 'This is normal,' 'They'll outgrow this,' 'Not to worry,'" said Alec Miller, a doctor of psychology and chief of child and adolescent psychology at Montefiore Medical Center and Albert Einstein College of Medicine in New York City. "As a parent you can really lose your compass about what's normal and typical when you have a range of behaviors coming at you."

"Parents tend to believe the myth that it's just a phase," agreed Dr. Harold S. Koplewicz, founder and director of the New York University Child Study Center and author of "More Than  Moody: Recognizing and Treating Adolescent Depression." And, he added, "The worst thing a parent can do is wait."

Many parents baffled by changes in their children's behavior seek out counseling on their own. One third of the queries to TeenTalk, which offers free phone and online counseling for teens are from parents, said officials with the project, run by the Ruth Rales Jewish Family Services of South Florida.

Barbara Hill watched as her son became more and more withdrawn, even from his friends. When she tried to broach the subject he was, by his own account, gruff and dismissive.

"Every time she tried to sit down and talk with me, I'd blow her off, or be real rude," said John, now 20.