Reflex vasodilation and sweating in response to passive whole-body heating are blunted in women with major depressive disorder

Major depressive disorder (MDD) is associated with alterations in the mechanistic regulation of body temperature, including altered circadian temperature profiles, reduced sweating, and blunted cutaneous vasodilation. Selective serotonin reuptake inhibitors (SSRIs) and serotonin norepinephrine reuptake inhibitors (SNRIs) may affect vascular function and sweating; however, heat stress thermoregulation in MDD and during SSRI or SNRI therapy has not been measured. The purpose of this study was to measure reflex cutaneous vasodilation and sweating responses during passive heating in women with MDD who were non- or chronically-treated with either SSRI or SNRI monotherapy. Sixteen women (aged 18-36 yrs) with unmedicated MDD, 16 women with SSRI-treated MDD, 16 women with SNRI-treated MDD, and 16 non-depressed women were passively heated using a water-perfused suit to increase core temperature (T c ) by 1.0°C. Forearm blood flow (FBF; venous occlusion plethysmography) was measured at every 0.1°C increase in T c , normalized to mean arterial pressure (MAP), and expressed as forearm vascular conductance (FVC). Skin blood flow (SkBF; laser-Doppler flowmetry) and local sweat rate (LSR; ventilated sweat capsule) were continuously measured. FVC was lower in unmedicated MDD compared to non-depressed (P=0.03) and SSRI-treated (P=0.01). FVC in SNRI-treated was not different from non-depressed (P=0.09) or MDD (P=1.0) but lower than SSRI-treated women (P=0.03). Greater increases in mean body temperature from baseline were required for onset of LSR and SkBF in unmedicated MDD compared to all other groups (all P<0.05). Together, these findings suggest alterations in reflex thermoregulation in unmedicated women with MDD; these effects may be ameliorated by antidepressant pharmacotherapies.