Monday, March 31, 2008

Depression and cortisol responses to psychological stress

Burke, H.M., Davis, M.C., Otte, C., & Mohr, D.C. (2005). Depression and cortisol responses to psychological stress: a meta-analysis. Psychoneuroendocrinology, 30, 846-856.

This meta-analysis pulled data from seven studies (196 participants with an average age of 40), each of which examined responses to psychological (non-pharmacological) stressors. Specifically, it examined the relationship between major depressive disorder (MDD) and levels of the stress hormone cortisol during three stages of experimentally-induced stress: (1) unstimulated 'baseline', (2) 'stress reactivity' in which cortisol increases from baseline, and (3) 'stress recovery' in which cortisol returns to baseline levels.

They concluded that at baseline MDD patients have lower cortisol levels than their non-depressed (ND) counterparts in morning studies and higher baseline cortisol levels than control groups in afternoon studies. This reveals somewhat opposite patterns of normal daily cortisol fluctuation (although some have described this as simply flattened diurnal activity). Therefore, it was critical to control for these baseline effects seen in the MDD group. After adjusting for these baseline effects, MDD individuals showed blunted stress reactivity and impaired stress recovery by comparison to controls.

Put simply, normal subjects show specific baseline patterns of cortisol release throughout the day and exhibit boosted cortisol levels and rapid recovery to baseline in response to stressors. These healthy cortisol activity curves are dynamic and responsive. MDD subjects, in contrast, show abnormal baseline patterns during the day and exhibit relatively flat and unresponsive patterns of cortisol secretion during and following stress. These effects were found to be most pronounced in older and more severely depressed patients. This altered hypothalamic-pituitary-adrenal (HPA) axis functioning appears somehow linked to depression.

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