Comparison 1.

Melatonin versus placebo

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Preoperative anxiety (VAS)	7	483	Mean Difference (IV, Random, 95% CI)	‐13.36 [‐16.13, ‐10.58]
1.1 Final VAS scores	5	385	Mean Difference (IV, Random, 95% CI)	‐13.48 [‐17.30, ‐9.66]
1.2 Change VAS scores	2	98	Mean Difference (IV, Random, 95% CI)	‐12.37 [‐16.23, ‐8.51]
2 Sensitivity analysis ‐ preoperative anxiety (VAS)	5	238	Mean Difference (IV, Random, 95% CI)	‐11.24 [‐14.04, ‐8.44]
2.1 Final VAS scores	3	140	Mean Difference (IV, Random, 95% CI)	‐10.0 [‐14.06, ‐5.94]
2.2 Change VAS scores	2	98	Mean Difference (IV, Random, 95% CI)	‐12.37 [‐16.23, ‐8.51]
3 Postoperative anxiety (VAS)	4	296	Mean Difference (IV, Random, 95% CI)	‐3.71 [‐9.26, 1.84]
3.1 Final VAS scores	2	198	Mean Difference (IV, Random, 95% CI)	‐5.14 [‐14.93, 4.66]
3.2 Change VAS scores	2	98	Mean Difference (IV, Random, 95% CI)	‐1.20 [‐4.75, 2.35]
4 Postoperative anxiety (STAI)	2	73	Mean Difference (IV, Random, 95% CI)	‐5.31 [‐8.78, ‐1.84]
5 Sensitivity analysis ‐ postoperative anxiety (VAS)	2	98	Mean Difference (IV, Random, 95% CI)	‐1.20 [‐4.75, 2.35]