Psychiatrists from Cardiff University invited 3,117 people living in South Wales and being treated for depression by their GP to take part in the study. In total, 576 people (18.5% of those invited) agreed to take part and completed a questionnaire to determine if they had symptoms of bipolar disorder. 370 of the respondents were then invited for a face-to-face clinical assessment, and 154 agreed. The researchers found that 29 of the 154 people assessed (18.8%) met the diagnostic criteria for bipolar disorder.
The researchers used these data to make three estimates of how many patients being treated in primary care for depression may have undiagnosed bipolar disorder. Their most conservative estimate is of 3.3%, based on the assumption that all the people who dropped out of the study by not returning their questionnaires or being assessed did not have bipolar disorder.
Their least conservative estimate, which assumes that all the people who did not drop out would have responded in the same way as those who were assessed, is 21.6%. The researchers’ more conservative mid-estimate is of 9.6%.
Lead researcher Dr Daniel Smith said: “Our study suggests that between 3.3% and 21.6% of primary care patients with depression may have unrecognised bipolar disorder. It is likely that many people being treated for depression by their GP will have been prescribed antidepressants. For people who in fact have undiagnosed bipolar disorder, these drugs may be at best unhelpful and at worst harmful.
“Our findings have real implications for the way in which GPs approach the diagnosis and treatment of patients with depression. We know that many patients with bipolar disorder are not correctly diagnosed for many years. It’s therefore important that the possibility of undiagnosed bipolar disorder is given greater recognition in primary care, and that GPs are supported in developing strategies to ensure that their patients with depression receive the correct diagnosis.”
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Smith DJ, Griffiths E, Kelly M, Hood K, Craddock N and Simpson SA. Unrecognised bipolar disorder in primary care patients with depression. British Journal of Psychiatry, ePub ahead of print (doi:10.1192/bjp.bp.110.083840).