Seven RCTs (221 participants) were included in the review; three parallel studies and four crossover studies. The mean quality score was 3.8 out of 5 (range 3 to 5).
There were non-significant decreases in systolic and diastolic blood pressure associated with melatonin treatment compared to placebo observed across the seven studies. There were no statistically significant changes in systolic or diastolic blood pressure observed with the use of fast-release melatonin.
The use of controlled-release melatonin was associated with statistically significant decreases in systolic blood pressure (WMD -6.1mmHg, 95% CI -10.69 to -1.50) and diastolic blood pressure (WMD -3.51mmHg, 95% CI -6.14 to -0.86).
There were no serious adverse events reported across the seven trials. Headache, drowsiness, weakness and nightmares were reported in three studies.