Fourteen studies, including 23 comparisons, were included in the review. The total number of patients included in the review was not reported. This could not be calculated from the tables, as it was unclear whether some studies assessing a number of treatment comparisons had used the same patients. Four comparisons were treatment versus control. The remaining 19 comparisons were pre-post design. Sample sizes ranged from five to 104 participants in each comparison.
Tricyclic antidepressants:
Ten comparisons were available for investigating tricyclic antidepressants. In the short recording studies (eight comparisons), tricyclic antidepressants led to decrease in all measures of heart rate variability reported and a significant (20.8%) increase in heart rate (p<0.001). Mean effect sizes ranged from 2.40 to 9.32. In the long recording studies (two comparisons), changes were small and inconsistent.
Selective serotonin reuptake inhibitors:
Seven comparisons were available for investigating selective serotonin reuptake inhibitors. In the short recording studies (five comparisons), selective serotonin reuptake inhibitors led to a significant decrease (-2%) in heart rate (p=0.01) in all five studies. The only change in heart rate variability was a marginally significant increase in the standard deviation of all NN intervals (p=0.07). In the long recording studies (two comparisons), results were contradictory.
Other treatments
A decrease in heart rate were seen using nefazodone (one comparison, -5.9% change, p<0.05) and an increase using mirtazapine (one comparison, 15.29% change, p<0.05). Decreases in all reported measures of heart rate variability were seen with bupropion and mirtazapine (both included one comparison). No significant effects were seen using electroconvulsive therapy or reboxetine.