Depressive and manic symptoms “not opposite poles in BD”
MedWire News: Depression and mania are independent symptoms and do not occupy opposite poles of the same dimension in bipolar disorder, research suggests.
Writing in the journal Acta Psychiatrica Scandinavica, Sheri Johnson (University of California, Berkeley, USA) and team explain: "For the past 100 years, models of bipolar disorder have assumed that depression and mania are opposite ends of a single continuum. Even the name 'bipolar disorder' implies a single dimension."
But they add: "Despite the influence of this model, relatively few studies have tested its core assumption - that manic and depressive symptoms are inversely related."
To investigate further, the researchers studied 236 patients with bipolar disorder (64% women) who were aged an average of 41.2 years. Of the participants, 221 (94%) met criteria for bipolar I disorder.
The participants completed the Structured Clinical Interview for DSM-IV at baseline and were followed up for 18 months. The occurrence and severity of depressive and manic symptoms were recorded every 8 weeks during follow up using the Longitudinal Interval Follow-up Evaluation-II.
Two parallel models were used to examine how depressive and manic symptoms correlated over time in the patients, with manic symptoms as the outcome variable in one model and depressive symptoms as the outcome variable in the other.
Overall, 91.5% of patients reported at least some depressive symptoms, and 69.5% reported at least some manic symptoms during the follow-up period.
Using random effects regression analysis, the researchers found that depression scores accounted for very little of the variance in mania scores. Similarly, mania scores were very small and accounted for very little of the variance in depression scores.
The findings were not consistent with the hypothesized inverse relationship, the researchers note.
Johnson and team conclude: "Our finding that depression and mania do not function as opposite poles adds to a growing body of studies questioning the conceptualization of bipolar disorders."
They add: "We hope that our findings stimulate more research on how mania and depression relate within bipolar disorder."
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By Mark Cowen