A seasonal effect on cortisol levels in patients with major depression
Leo Sher, M.D.
Our research paper, “Higher cortisol levels in spring and fall in patients with major depression” was published 15 years ago in the May 2005 issue of Progress in Neuro-Psychopharmacology & Biological Psychiatry (1). We examined 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). The seasons were defined by the equinoxes and solstices: Winter lasts from 21 December to 21 March, Spring from 22 March to 20 June, Summer from 21 June to 20 September, and Fall from 21 September to 20 December. We evaluated multiple clinical parameters including 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 hours 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. We did not find seasonal effects on baseline prolactin levels, or post-challenge cortisol and prolactin levels. We observed no statistically significant effects of seasons on severity of depression or other clinical parameters.
Our finding that baseline plasma cortisol levels are higher in the Spring/Fall group than in the Winter/Summer group suggests that these two groups may represent different biological subtypes of major depression. Our finding also indicates that seasonal variations in cortisol levels may affect adrenal response and need to be accounted for in research studies.
- Sher L, Oquendo MA, Galfalvy HC, Zalsman G, Cooper TB, Mann JJ. Higher cortisol levels in spring and fall in patients with major depression. Prog Neuropsychopharmacol Biol Psychiatry. 2005 May;29(4):529-34. doi: 10.1016/j.pnpbp.2005.01.011.