Epidemiology
12 years ago
When broadly defined 4% of people experience bipolar at some point in their life. The lifetime prevalence of bipolar disorder type I, which includes at least a lifetime manic episode, has generally been estimated at 2%. It is equally prevalent in men and women and is found across all cultures and ethnic groups.
A reanalysis of data from the National Epidemiological Catchment Area survey in the United States, however, suggested that 0.8 percent experience a manic episode at least once (the diagnostic threshold for bipolar I) and 0.5 a hypomanic episode (the diagnostic threshold for bipolar II or cyclothymia). Including sub-threshold diagnostic criteria, such as one or two symptoms over a short time-period, an additional 5.1 percent of the population, adding up to a total of 6.4 percent, were classed as having a bipolar spectrum disorder. A more recent analysis of data from a second US National Comorbidity Survey found that 1% met lifetime prevalence criteria for bipolar 1, 1.1% for bipolar II, and 2.4% for subthreshold symptoms. There are conceptual and methodological limitations and variations in the findings. Prevalence studies of bipolar disorder are typically carried out by lay interviewers who follow fully structured/fixed interview schemes; responses to single items from such interviews may suffer limited validity. In addition, diagnosis and prevalence rates are dependent on whether a categorical or spectrum approach is used. Concerns have arisen about the potential for both underdiagnosis and overdiagnosis.
Late adolescence and early adulthood are peak years for the onset of bipolar disorder. One study also found that in 10% of bi-polar cases, the onset of mania had happened after the patient had turned 50.
A reanalysis of data from the National Epidemiological Catchment Area survey in the United States, however, suggested that 0.8 percent experience a manic episode at least once (the diagnostic threshold for bipolar I) and 0.5 a hypomanic episode (the diagnostic threshold for bipolar II or cyclothymia). Including sub-threshold diagnostic criteria, such as one or two symptoms over a short time-period, an additional 5.1 percent of the population, adding up to a total of 6.4 percent, were classed as having a bipolar spectrum disorder. A more recent analysis of data from a second US National Comorbidity Survey found that 1% met lifetime prevalence criteria for bipolar 1, 1.1% for bipolar II, and 2.4% for subthreshold symptoms. There are conceptual and methodological limitations and variations in the findings. Prevalence studies of bipolar disorder are typically carried out by lay interviewers who follow fully structured/fixed interview schemes; responses to single items from such interviews may suffer limited validity. In addition, diagnosis and prevalence rates are dependent on whether a categorical or spectrum approach is used. Concerns have arisen about the potential for both underdiagnosis and overdiagnosis.
Late adolescence and early adulthood are peak years for the onset of bipolar disorder. One study also found that in 10% of bi-polar cases, the onset of mania had happened after the patient had turned 50.