Most children who qualify for the diagnosis do not proceed to develop the classic features of adult bipolar disorder like mania, researchers have found. They are far more likely to become depressed.

Dr. Mani Pavuluri, director of the pediatric mood disorders program at the University of Illinois, Chicago, said the label was often better than any of the other diagnoses often given to difficult children.

"These are kids that have rage, anger, bubbling emotions that are just intolerable for them, and it is good that this is finally being recognized as part of a single disorder," Pavuluri said.

"I have been studying trends in mental health services for some time, and this finding really stands out as one of the most striking increases in this short a time," said Dr. Mark Olfson of the New York State Psychiatric Institute at the Columbia University Medical Center, the senior author of the study.

The increase makes bipolar disorder more common among children than clinical depression, the authors said. Psychiatrists made almost 90 percent of the diagnoses, and two-thirds of the young patients were boys, says the study, published in the September issue of The Archives of General Psychiatry. About half the patients were identified as having other mental difficulties, most often attention deficit disorder.

The children's treatments almost always included medication. About half received antipsychotic drugs like Risperdal from Janssen or Seroquel from Astrazeneca, both developed to treat schizophrenia. A third were prescribed so-called mood stabilizers, most often the epilepsy drug Depakote. Antidepressants and stimulants were also common.

Most children took a combination of two or more drugs, and four in 10 received psychotherapy.

The regimens were similar to those of a group of adults with bipolar diagnoses, the study found.

"You get the sense looking at the data that doctors are generalizing from the adult literature and applying the same principles to children," Olfson said.

The increased children's diagnoses reflect several factors, experts say. Symptoms appear earlier in life than previously thought, in teenagers and young children who later develop the full-scale disorder, recent studies suggest.

The label also gives doctors and desperate parents a quick way to try to manage children's rages and outbursts in an era when long-term psychotherapy and hospital care are less accessible, they say.

In addition, drugmakers and company-sponsored psychiatrists have been encouraging doctors to look for the disorder since several drugs were approved to treat it in adults.