Study	Reason for exclusion
Borazan 2010	Intervention was not aimed at treating pre‐ or postoperative anxiety
Evagelidis 2009	Intervention was not aimed at treating pre‐ or postoperative anxiety
Hansen 2014	Too long treatment with melatonin preoperatively
Johns 2012	Intervention was not aimed at treating pre‐ or postoperative anxiety
Nasr 2014	There was neither a placebo nor a benzodiazepine group
Peng 2010	Study was terminated prematurely and data will not be published (according to first author ‐ contacted by e‐mail July 2013)
Radwan 2010	Intervention was not aimed at treating pre‐ or postoperative anxiety
Wawrzyniak 2014	There was neither a placebo nor a benzodiazepine group
Yoo 2013	Intervention was not aimed at treating pre‐ or postoperative anxiety

ASA: American Society of Anaesthesiologists physical status classification

M: Male

F: Female

min: minutes

mg: milligram

μg: microgram