What is the role of environmental factors in the etiology of bipolar affective disorder (manic-depressive illness)?

Updated: May 30, 2019
  • Author: Stephen Soreff, MD; Chief Editor: Glen L Xiong, MD  more...
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In some instances, the cycle may be directly linked to external stresses or the external pressures may serve to exacerbate some underlying genetic or biochemical predisposition. For example, pregnancy is a particular stress for women with a manic-depressive illness history and increases the possibility of postpartum psychosis. [55]

Because of the nature of their work, certain individuals have periods of high demands followed by periods of few requirements. For example, a landscaper and gardener who was busy in the spring, summer, and fall became relatively inactive during the winter, except for plowing snow. Consequently, he appeared manic for a good part of the year, and then he would crash and hibernate during the cold months.

There have been a number of studies linking bipolar disorder and increased amount of sunlight during the day (aka, springtime). In one study, researchers collected data from 5536 patients at 50 sites in 32 countries on six continents; onset of bipolar disorder occurred at 456 locations in 57 countries. Results show a significant, inverse association between the maximum monthly increase in solar insolation at the onset location, and the age of onset. The study suggests that a large increase in springtime solar insolation may impact the onset of bipolar disorder, particularly in those patients with a family history of mood disorders. [56]

Futhermore, another study assessed psychiatric admission of 730 patients and found the admission rate for patients with bipolar disorder was significantly higher during May, June, and July; months with maximum sunlight exposure. These findings suggest photoperiod is a key element in bipolar disorder. [57]

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