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FRIDAY, June 17 (HealthDay News) -- An estimated 4.3 percent of Americans suffer from bipolar disorder or its milder forms, far more than previous estimates which placed the number at about 1 percent, a new study finds.
"When the entire spectrum [of bipolar disorder] is taken into account, the percent affected by that syndrome is higher than was recognized," said Ronald C. Kessler, professor of health care policy at Harvard Medical School. He presented the findings Friday at the Sixth International Conference on Bipolar Disorder, in Pittsburgh.
The new estimate finds that 4.3 percent of adults suffer from a bipolar disorder or a "sub-threshold" bipolar disorder, Kessler said. The latter group includes persons who don't fit the precise clinical criteria for bipolar disorder but who have symptoms nearly as bad that severely affect their ability to perform their daily routine.
Previous studies had estimated that 1 percent of adults suffer from bipolar disorder, also known as manic-depressive illness, which is characterized by unusual shifts in a person's mood, energy and ability to function. But those calculations didn't take into account the milder forms of the illness, Kessler said.
"We interviewed nearly 10,000 people," he said. "It cost $20 million to do the study. We also came up with new estimates of workplace cost of the illness."
The cost to the nation of bipolar disorder is close to $26 billion annually, a figure not calculated until this study, he added.
Bipolar disorders are classified as bipolar I or II, Kessler said. In bipolar I, "the basic definition is having an episode of euphoria or irritability that lasts at least seven days and is accompanied by at least four other symptoms, such as getting into fights, not needing to sleep, thinking you have supernatural powers."
"Biopolar II [symptoms] lasts three or four days and has to have a smaller number of symptoms and lower impairment," he said. "The person must also have a history of depression."
The sub-threshold forms "don't meet either of these definitions but almost do," he said.
When Kessler's team looked at the impact on the workplace, it found the mean number of lost days per year for someone with bipolar disorder was 49.5, compared to 31.9 for someone with major depressive disorder. Kessler said bipolar problems tend to be more chronic than depression.
That helps to explain the nearly $26 billion annual price tag, Kessler said.
A big part of the cost of bipolar problems is suicide, Kessler's team found. The chances of successful suicide attempts by bipolar patients are much higher than in the general population. One in five attempts by bipolar patients ends in death, he said, compared to one in 20 attempts in the general population.
Another study presented at the conference found that bipolar patients who took lithium, an older drug less prescribed now than in the past, had an 80 percent to 85 percent lower rate of suicide attempts or completed suicides, compared to bipolar patients not on the drug. The study was led by Dr. Ross J. Baldessarini, a professor of psychiatry at Harvard Medical School.
Kessler said employers who host depression screenings should consider expanding them to include testing for bipolar disorder. "There is an awful lot of interest in depression screening. We really need to broaden that to include people with bipolar and the bipolar spectrum."
In a typical year, Kessler said, 6 percent of the U.S. population meets the criteria for major depression, and 2.5 percent for bipolar problems, making bipolar more common than previously thought.
The Kessler research findings are consistent with what experts observe clinically, said another expert, Ellen Frank, a professor of psychiatry and psychology at the University of Pittsburgh School of Medicine.
"The important part of the study is that these sub-threshold forms of bipolar are associated with substantial amounts of impairment, and that the problems associated with these forms are almost as great as those associated with bipolar I and II disorders."
According to the National Institute of Mental Health, most people with bipolar disorder can successfully manage their mood swings with proper treatment, including medication and psychotherapy.
More information
To learn more about bipolar disorder, visit the National Institute of Mental Health (www.nimh.nih.gov ).
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