UK researchers believe as many as 1 in 4 people diagnosed in primary care with major depressive disorder may actually have bipolar disorder.
In a new study, scientists administered bipolar assessments to nearly 800 patients receiving care for depression. Remarkably, 24 percent of the patients reported a previous episode of mania or mild mania suggesting that they may actually have bipolar disorder rather than depression.
Bipolar disorder is a serious and chronic psychiatric illness, associated with high risk of suicide and other disorders. It is characterized by both manic and depressive episodes.
Evidence shows that misdiagnosis of bipolar disorder is common, and that the diagnosis is made, on average, as many as 10 years after the onset of symptoms. The most common misdiagnosis is with unipolar depression, which is characterized by depressed mood without manic episodes.
The aims of this study were to determine the proportion of patients who are diagnosed with unipolar depression in primary care, but who actually have bipolar disorder and may be receiving inappropriate and harmful treatment. Evidence shows that some antidepressants can induce mania.
The cross-sectional survey of primary care patients is being conducted at the Neasham Road surgery in Darlington in the UK. Those patients with existing bipolar disorder were excluded from the study.
790 patients who had a diagnosis of unipolar depression using primary care diagnostic methods were included in the study.
The researchers used 3 questionnaires:
- the Mood Disorder Questionnaire, designed to measure the rate of bipolar disorder in the target group
- the Work and Social Adjustment Scale, designed to measure and compare social functioning deficits between unipolar and bipolar patients
- the Cognitive Failures Questionnaire, designed to measure and compare cognitive impairment between the 2 groups.
Evidence suggests that psychosocial and neurocognitive impairment may be more pronounced in patients with bipolar disorder.
278 questionnaires were returned. Of these, 24 percent were found to have had a previous episode of mania or mild mania. The researchers are currently in the process of making a clinical diagnosis of these patients.
Subsequent interviews and analysis will provide information about the prevalence of bipolar disorder in patients diagnosed with depression, and about the occupational and neuropsychiatric impact of this disorder compared with major depressive disorder.