Researchers from the National Institute of Mental Health report approximately 4.4 percent of U.S. adults may have a form of bipolar disorder during some point in their lifetime including about 2.4 percent with a “sub-threshold” condition. Prior research estimated that about 1 percent of adults have experienced bipolar disorder.
The four-fold increase in prevalence was discovered from interviews of over 9,000 individuals chosen to represent the general population.
According to the authors of the study, the new evidence suggests the current diagnostic criteria may be too narrow to effectively detect bipolar disorder in the general population, and that a broader definition of bipolar spectrum disorder would identify many more individuals with bipolar symptoms.
The study is published in the May issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
Individuals with bipolar disorder tend to fluctuate between periods of mania—an inappropriately elevated mood, characterized by impulsive behavior and an increased activity level—and periods of depression. They are at increased risk of suicide and other medical problems, such as cardiovascular disease, according to background information in the article.
Kathleen R. Merikangas, Ph.D., National Institute of Mental Health, Bethesda, Md., and colleagues estimated the national prevalence of bipolar disorder using data from 9,282 individuals chosen to represent the general population.
The researchers conducted interviews between February 2001 and April 2003 to assess the presence of bipolar disorder and other psychiatric conditions.
Participants were classified as having bipolar disorder I, characterized by at least one episode of mania and one of depression; bipolar disorder II, requiring an episode of depression plus hypomania, a milder form of mania that does not require hospitalization; and a milder, sub-threshold bipolar disorder that involves hypomania with or without depression, otherwise classified as bipolar disorder “not otherwise specified” in the current diagnostic nomenclature of the American Psychiatric Association.
The study found that:
“The present results reinforce the argument of other researchers that clinically significant sub-threshold bipolar disorder is as least as common as threshold bipolar disorder,” the authors write.
“Although most individuals with bipolar disorder receive treatment owing to co-morbid disorders, the lack of recognition of their underlying bipolarity leads to only a few receiving appropriate treatment.”
The findings suggest that a substantial proportion of those diagnosed with major depression may actually have a form of bipolar disorder.
More individuals with other psychiatric disorders should also be screened for bipolar disorder, the authors conclude.
“Additional research is needed to resolve uncertainty regarding the most appropriate threshold and boundary distinctions for bipolar disorder. This uncertainty remains a major impediment to advancing the understanding of the bipolar disorder spectrum in the population.”
Source: JAMA and Archives Journals