Higher cortisol levels in spring and fall in patients with major depression

Multiple lines of evidence suggest that there are seasonal effects on mood and behavior, and that these effects are related to serotonergic and hypothalamic-pituitary-adrenal (HPA) function. This study sought to determine whether there is a seasonal effect on clinical parameters, baseline cortisol and prolactin levels, and cortisol and prolactin responses to fenfluramine administration in subjects with major depression.

In all, 136 subjects with major depression entered the study. Sixty-two subjects who had a major depressive episode (MDE) in Spring or in Fall (the Spring/Fall group) were compared to 74 subjects who had MDE in Winter or in Summer (the Winter/Summer group). Demographic and clinical parameters were assessed and recorded. Clinical parameters included depression, aggression, impulsivity, hopelessness, hostility, and current suicide ideation rating scales, suicide attempt status, and number and maximum lethality of suicide attempts. Cortisol and prolactin levels were drawn before fenfluramine administration and hourly for 5 h thereafter. Cortisol and prolactin levels were computed as the area under the curve of hourly cortisol measurements.

Baseline cortisol levels were significantly higher in the Spring/Fall group compared to the Winter/Summer group (14.1+/-4.5 ng/ml vs. 12.5+/-4.4 ng/ml, df=132, t=2.16, p=0.03). There were no seasonal effects on baseline prolactin levels, or post-challenge cortisol and prolactin levels.

The Spring/Fall group and the Winter/Summer group may represent different subtypes of major depression. Future studies need to both confirm our results and elucidate the mechanism of the circannual effect on biological function in depressed patients. The results of our study underline the importance of considering seasonality in psychobiology.