Studies on the cholesterol-serotonin hypothesis and its link to mood disorders are scarce. In addition, little is known about the association between cholesterol and the effects of tryptophan depletion (TD). The aim of the present study was to investigate the association between plasma cholesterol and changes in heart rate variability (HRV), an important marker of depression and anxiety, after TD. The plasma cholesterol levels of 28 healthy participants were noted, and their HRVs were measured by spectrum analysis. TD was carried out on testing day, and participants provided blood samples just before and 5 hours for tryptophan level after TD. HRV was measured again after TD. An association was found between plasma cholesterol levels and the change in HRV. Decreased high frequency HRV was marginally associated with lower levels of high-density lipoprotein cholesterol, while increased low frequency HRV was significantly associated with lower levels of total and low-density lipoprotein cholesterol. Our findings indicate that low cholesterol levels may play parts of role in the mechanism of the deactivation of parasympathetic, and activation of sympathetic, functions induced by altered serotonergic function.
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