I read with interest the article by Altinbas et al. (in this issue) suggesting that the prevalence of the metabolic syndrome in individuals with bipolar disorder is influenced by seasonality, with higher rates reported in the winter and spring months. They further opine that temperamental dimensions (e.g. depression) constitute a vulnerability factor to the seasonal influence. The article is appropriate in highlighting that their small sample size, open label design and absence of a control group, among other limitations, affect the inferences that can be drawn from their outcome. Their paper is hypothesis-generating rather than hypothesis-confirming.
The authors remind us that environmental factors (e.g. seasonality) affect susceptibility to allostatic load. It is amply documented that bipolar symptoms/episodes are affected by seasonality in susceptible subsets. It could be conceptualized that metabolic syndrome (e.g. obesity) is a phenotypic manifestation of an abnormal stress response with somatic manifestations. It would be interesting to know whether individuals with metabolic syndrome seasonality are more or less likely to also experience breakthrough symptomatology.
There is tremendous interest in conceptualizing bipolar disorder as progressive disorders.1 I would conjecture that obesity and associated metabolic abnormalities are a cause and consequence of progression in bipolarity.232-4 Indeed, this remains a testable hypothesis. My clinical impression is that individuals with bipolar disorder who exhibit susceptibility to symptomatic recurrence as a function of seasonality often present with “mixed presentations.”5 It is tempting to further speculate that obesity, which is depressogenic, may be affecting the symptomatic presentation of bipolar disorder, increasing the likelihood that these patients will present as “mixed.” Again, my clinical impression is that bipolar patients that I have encountered over the last decade are more often mixed than they are euphoric, and I have wondered whether, in addition to the inappropriate use of antidepressants, obesity is changing the “face” of bipolar disorder.
I further applaud the authors for reminding us of possible temperamental contributions and giving us a “dose of reality” that there will be no unidimensional explanation for psychiatric disorders that is coherent, comprehensive, and explanatory.