The number of teenagers who have experienced mania, a hallmark of bipolar disorder, is close to the number of adults estimated to have the mood disorder, suggesting that for many the condition begins during adolescence, according to a US study.
"The traditional wisdom has been that mania begins in your 20s and 30s," said Kathleen Ries Merikangas, the study's lead author and chief of the genetic epidemiology branch at the National Institute of Mental Health.
"I think the important thing is for people to recognize that mania does occur in adolescents."
The most common definition of bipolar disorder includes alternate cycles of mania and depression, though one type of bipolar diagnosis involves mania alone.
The study, published in the Archives of General Psychiatry, included more than 10,000 teenagers who went through extensive interviews about their moods and behavior.
The researchers found that 2.5 per cent met the criteria for having had mania and depression, and 2.2 per cent of teens had experienced it within the last 12 months.
Also, within the year preceding the survey, 1.3 per cent of the teens had mania alone and 5.7 per cent had depression.
According to the National Institute of Mental Health, 2.6 per cent of adults have had bipolar disorder in the last 12 months.
"I think our data suggest that bipolar disorder is more common in adolescents than previous studies had shown,"Merikangas told Reuters Health.
She said it could be because the questions used during the interviews were somewhat broader than what earlier surveys had asked, but all the teens considered to have a mood disorder in her study met the criteria for diagnosis in the DSM-IV, the standard diagnostic manual for psychiatry.
"This (study) confirms the impression that onset in adolescents is part of the picture for this disorder for many, many patients," said Robert Finding, director of the division of child and adolescent psychiatry at University Hospitals Case Medical Center in Cleveland, who was not involved with the study.
The mood disorders also became more common as the teens got older, with 1.4 per cent of 13 and 14-year-olds meeting the criteria for mania - but nearly twice as many 17 and 18 year olds had the disorder.
About one out of every five teens with mania and depression had made a suicide attempt, and more than half had an anxiety or behavioral disorder as well.
Experts said that the study results don't necessarily suggest that the rates of bipolar symptoms in teens are rising but more likely that increasing numbers of teens who seek treatment for a psychiatric problem are being diagnosed with bipolar disorder.
"The take home message is that adolescence is when we really see bipolar disorder begin, so we should shift our focus of prevention and intervention earlier in the lifespan," Merikangas said.