|
IS
BIPOLAR DISORDER MORE PREVALENT THAN BELIEVED?
PHILADELPHIA—
The prevalence of bipolar disorders in the United States is almost three times greater than previously reported, according to new data. Prevalence rates are highest among young adults, those with lower incomes, and those living in rural areas or small cities. In addition, researchers found that only one in five study participants who screened positive for bipolar disorders had been previously diagnosed with the disorder by a health care professional, and one third were diagnosed as having unipolar depression.
“These findings suggest that bipolar disorders are under-recognized, under-diagnosed, and potentially misdiagnosed,” stated lead author Robert M.A. Hirschfeld, MD, Titus Harris Chair and Professor and Chair of Psychiatry and Behavioral Sciences at the University of Texas Medical Branch in Galveston. He presented his team’s findings at the 2002 Annual Meeting of the American Psychiatric Association (APA).
The lifetime prevalence of DSM-III bipolar I disorder in the United States was previously estimated to be 1%. However, as Dr. Hirschfeld pointed out, bipolar disorder in general includes a much broader range of illness. Other studies regarding bipolar I and II disorders were “small and used varying definitions,” he said. Therefore, the investigators conducted a large-scale, epidemiologic study to estimate the lifetime prevalence of bipolar disorders.
The Mood Disorder Questionnaire (MDQ), a validated screening instrument for bipolar I and II disorders, was mailed to 127,800 adults 18 and older. The MDQ included 13 items about mood, self-confidence, energy, sociability, sex, loquaciousness, distractibility, and other behaviors. The survey also contained two questions about symptom co-occurrence and functional impairment. Some individuals who did not respond to the questionnaire were interviewed by telephone. An MDQ case was considered positive if the patient had seven or more symptoms/behaviors, co-occurrence of two or more symptoms/behaviors, and moderate or severe symptom-related impairment. In addition, post-survey weighting was used to balance the sample for age, sex, region, market size, and household size to reflect national demographics.
PROFILING BIPOLAR DISORDER
Dr. Hirschfeld and colleagues based their findings on 85,358 usable surveys from the MDQ screening and found an overall estimated 3.4% lifetime prevalence for bipolar I and II disorders. Men had an estimated 3.8% lifetime prevalence for bipolar I and II disorders, and women, 3.0%. Subjects between 18 and 24 had the highest rate (9.3%) of all age-groups. Individuals between ages 25 and 34 (3.9%) had the second highest rate, followed by the 35 to 44 age-group (3.2%), 45 to 54 (2.5%), 55 to 64 (1.5%), and those 65 and older (0.5%). As for ethnic groups, American Indians had the highest rate of bipolar disorders (7.6%), followed by African-Americans (4.3%), Asian/Pacific Islanders (4.1%), and whites (3.1%).
The region with the highest prevalence rate was the Southeast (5.0%), and the area with the lowest rate was New England (2.2%). Prevalence was highest in small cities with a population between 100,000 and 500,000 (4.4%) and in rural areas (4.1%). Urban areas with a population of more than two million had the lowest rate (2.7%). Prevalence of bipolar disorder was highest among those with a household income of less than $20,000 (5.7%); those making more than $85,000 had the lowest rate (1.9%). Furthermore, the more family members per household, the higher the prevalence rate of bipolar disorder. For example, a household of one had a prevalence of 2.5%; and a household of five or more, 4.8%.
The investigators found that just 19.8% of respondents who screened positive on the MDQ said that they had been previously diagnosed with bipolar disorder by a health care professional and 31.2% of respondents who screened positive reported a prior diagnosis of unipolar depression. Of MDQ-negative subjects, 1.4% reported a diagnosis of bipolar disorder, and 9.5% reported having been diagnosed with unipolar depression.
Dr. Hirschfeld’s team also determined that subjects with positive MDQ results were more likely to report comorbid medical illnesses. “Sizeable [greater than 10%] differences were found for hypertension, allergies, and alcohol/substance abuse. These subjects were twice as likely to report a history of asthma and migraine, and 36% of them had blood relatives with bipolar illness,” he said.
DOES BIPOLAR DISORDER HAVE A SEX BIAS?
Claudia F. Baldassano, MD, Assistant Professor of Psychiatry at the Hospital of the University of Pennsylvania in Philadelphia, and colleagues presented findings from their own separate study of bipolar disorder and sex differences. Using data collected from 499 men and women from the Systematic Treatment Enhancement Program for Bipolar Disorder, Dr. Baldassano’s team found that 29% of bipolar women had bipolar II disorder, compared with 15% of men. In addition, the investigators determined that about 85% of all men from the database had bipolar I disorder, as opposed to 68% of women. They also found that bipolar women were more likely than the general population to have a lifetime history of alcohol dependence, were more likely to commit suicide, and were more prone to develop thyroid disease. Bipolar women also received antidepressant medication more frequently than did men but did not have a higher rate of antidepressant-induced mania. However, bipolar men were more likely to have legal problems and a history of violence.
MOOD PATTERNS AMONG THE SEXES
Related findings on bipolar disorder were presented at the APA meeting by Natalie Rasgon, MD, PhD, Assistant Professor of Psychiatry at the University of California, Los Angeles, and colleagues, who found that women with bipolar disorder were more depressed and experienced more mood fluctuations than did men. Dr. Rasgon’s team analyzed, for a three-month period, the differences among mood, sleep, and medication patterns of 12 men and 26 women with bipolar disorder. They found that 80% of men were considered “normal” in terms of overall distribution of mood, compared with 59% of women. Nearly 33% of women were termed “depressed” compared with about 14% of men. The manic category included 8.8% of women and 6.2% of men. In addition, 86% of men reported no mood changes throughout the study period, whereas 75% of women experienced no such mood changes. In one example of a mood switch, 8.1% of women changed from normal to depressed, compared with 3.2% of men.
—Colby Stong
Suggested Reading
Hirschfeld RM, Williams JB, Spitzer RL, et al. Development and validation of a screening instrument for bipolar spectrum disorder: the Mood Disorder Questionnaire. Am J Psychiatry. 2000;157:1873-1875.
Tondo L, Baldessarini RJ. Rapid cycling in women and men with bipolar manic-depressive disorders. Am J Psychiatry. 1998;155:1434-1436.
Return to table of contents
|
|
