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Bipolar disorder often undiagnosed among primary care patients prescribed antidepressants

A “substantial proportion” of primary care patients prescribed antidepressants for depression or anxiety have undiagnosed bipolar disorder, according to data published in the British Journal of General Practice.

According to the researchers, clinicians should examine the past history of patients with anxiety and depression, to identify potential cases of bipolar disorder.

“When [bipolar disorder] presents with depression, as it often does, the diagnosis can be difficult,” Tom Hughes, MD, of the Leeds and York Partnership NHS Foundation Trust, at Saint Mary’s Hospital, in Leeds, United Kingdom, and colleagues wrote. “ … There are unresolved concerns that antidepressant treatment lacks a strong evidence base in bipolar depression, may increase the risk of relapse of mania or hypomania, or worsen the course of bipolar disorder.”

To measure the rate of undiagnosed cases of bipolar disorder among U.K. primary care patients prescribed antidepressants for depression or anxiety, and whether such patients suffer from more severe depression symptoms, the researchers conducted an observational study of cases at 21 general practices in West Yorkshire.  The study included patients aged 16 to 46 years who had been prescribed antidepressant medication.

The researchers recruited patients for the study through primary care databases, and conducted diagnostic interviews that included a screening questionnaire for bipolar disorder, the Mood Disorder Questionnaire (MDQ). The study cohort included 233 patients. The researchers then used The Health Improvement Network (THIN), which contains data from more than 415 general practices, to determine the representativeness of the study sample.

According to the researchers, the prevalence of undiagnosed bipolar disorder was 7.3% (95% CI, 4.4-11.1). After adjusting for differences between the study sample and the THIN database, the rate increased to 10%. In addition, those with unrecognized bipolar disorder were younger and had more severe lifetime depression. In addition, the researchers judged the predictive value of the MDQ to be “poor.”

“The present data are consistent with the view that antidepressants alone, without concurrent mood-stabilizing or antimanic medication, are less effective in bipolar II depression than in unipolar depression,” Hughes and colleagues wrote. “Better data are required on which treatments are effective for this group, from samples of people with bipolar II rather than bipolar I disorder or unipolar depression.” – Jason Laday