We were most interested to read the recent report by Licht et al. on the impact of a variety of antidepressants on heart rate variability (HRV), a robust predictor of sudden cardiac death and future mortality. Longitudinal evidence was reported for the effects of antidepressants including tricyclics (TCAs), serotonergic and noradrenaline reuptake inhibitors (SNRIs), and serotonergic reuptake inhibitors (SSRIs) on HRV. New users of TCAs (n = 12) displayed a decrease in respiratory sinus arrhythmia (RSA) (an indicator of HRV that controls for respiration rate) of 23 msec over the 2-year assessment period; new users of SNRIs (n = 23) displayed a decrease of 12 msec; and new users of SSRIs (n = 74) displayed a decrease of 7 msec, compared with persistent non-users of medication. New users of TCAs also displayed an increase in heart rate of 7 bpm over the 2-year assessment period, and new users of SNRIs displayed an increase of 8 bpm. By contrast, new users of SSRIs displayed a small decrease in heart rate of 1.5 bpm. While the impact of antidepressant medication on HRV is an important matter, we have a number of concerns relating to the report by Licht et al. These include inappropriate use of analysis of covariance (ANCOVA), inclusion of patients with a prior history of cardiovascular disease, and the inferences drawn pertaining to SSRI medication use.
Kemp, A.H., Quintana, D.S., Mahli, G.S. (2011). Effects of Serotonin Reuptake Inhibitors on Heart Rate Variability: Methodological Issues, Medical Comorbidity, and Clinical Relevance. Biological Psychiatry, 69(8); e25-e26.