Saturday, January 9, 2010

The Bipolar Spectrum

Over the past decade there has been an effort on the part of some psychiatric researchers to expand the boundaries of bipolar disorder. The most recent salvo is a paper published in the Archives of General Psychiatry in December. The title is: Heterogeneity of DSM-IV major depressive disorder as a consequence of subthreshold bipolarity. The study uses data from a longitudinal psychiatric epidemiological study conducted in Germany. About half of people diagnosed at a baseline interview with major depressive disorder had "subthreshold bipolarity" meaning that they had some symptoms of hypomania (a milder disturbance than the manic episodes seen in Bipolar disorders). This subset was found to more often have a family history of bipolar disorder (5.9% vs. 1.9%) and more often converted to bipolar disorder (7.2% vs. 1.7%), among other differences. Based on this, the authors imply that people with major depressive disorder should be more carefully screened for subthreshold bipolarity so that they can be receive more "adequate treatment." They do not emphasize the reality that more than 90% of this subthreshold group did not have a family history of bipolar disorder and did not convert to a bipolar disorder. These recommendations are, in my view, somewhat reckless. In the absence of evidence from randomized controlled trials that treating people with subthreshold bipolar symptoms as if they had a bipolar disorder leads to better outcomes that treating them as if they had a major depressive disorder. This is a strange deviation from accepted principles of evidence-based medicine and surprising to see in the world's most highly ranked psychiatry journal.