Sex differences in cardiac autonomic function of depressed young adults

► Heart rate variability of depressed adults under orthostatic stress was examined. ► Depressed males showed reduced HRV and parasympathetic activity. ► Reduced HRV and increased LF/HF in males linked to higher cardiovascular risk. ► The relationship between depression and cardiac dysfunction may be sex-dependent. Cardiac autonomic dysfunction has been proposed as an important contributing factor to the increased cardiovascular risk observed in major depression (MDD). However, the evidence regarding alterations in heart rate variability (HRV) in otherwise healthy depressed subjects has been inconclusive. A case–control study in 50 treatment-naïve young adults with a first MDD episode without comorbid psychiatric disorders and 50 healthy control subjects was conducted. Time- and frequency-domain indexes of HRV were determined at baseline supine and after 5-min of orthostatic stress at 60°. There were no significant differences in the time- or frequency-domain variables of HRV between depressed patients and controls. However, a random-effect ANOVA model showed that during orthostatic stress depressed men had a reduced HRV and decreased parasympathetic activity compared to control subjects, while no differences were found between depressed women and controls. These results suggest a sex-dependent relationship between major depression and cardiac autonomic dysfunction and provide one potential explanation for sex differences in the association of depressive symptoms with cardiovascular morbidity.