Table 4.

Cognitive function

Ref.	Sample size (sex) melatonin; control	Age (yr) melatonin; control	Dose, duration	Diagnosis	Inclusion criteria	Study design	Outcomes	Significant findings related to melatonin	Risk of bias
Shirayama et al[29], 2014	10 (NR); -	42.5 ± 7.3	8 mg/d melatonin for 6 mo	SCZ (n = 10)	Diagnosis of SCZ (as per DSM-IV criteria); symptoms stable for 3 mo	Open-label study	TMT (A and B), WCST, VFT, Stroop Test, DSPDT, IGT, RAVLT	RAVLT (total, delayed recall and recognition): Improved at 6-mo compared to baseline	High
Baandrup et al[30], 2017	40 (21 M, 19 F); 40 (24 M, 16 F)	47.4 ± 8.6; 49.0 ± 12.1	2 mg/d CR melatonin or placebo for 24 wk	Paranoid SCZ (n = 62), non-paranoid SCZ (n = 6), SZA (n = 3), BP (n = 9)	Diagnosis of SCZ, SZA or BP (as per ICD-10 criteria); treated with 1 antipsychotic and 1 BZD for 3 mo	Randomized, double-blind clinical trial	BACS (domains: verbal memory, working memory, motor speed, verbal fluency, letter fluency, attention and processing speed, executive function), WHO-Five WBI, SWN, PSP, UKU, PANSS	-	Low

BACS: Brief assessment of cognition in schizophrenia; BP: Bipolar disorder; BZD: Benzodiazepine; CR: Controlled-release; DSM-IV: Diagnostic and Statistical Manual of Mental Disorders, fourth edition; DSPDT: Digit span distraction test; F: Female; ICD-10: International Classification of Diseases, Tenth Revision; IGT: Iowa gambling task; M: Male; NR: Not reported; PANSS: Positive and negative syndrome scale; PSP: Personal and social performance scale; RAVLT: Rey auditory verbal learning test; SCZ: Schizophrenia; SWN: Subjective wellbeing under neuroleptic treatment scale; SZA: Schizoaffective disorder; TMT: Trail-making test; part A and part B; UKU: Udvalget for Kliniske Undersoegelser side effect rating scale; VFT: Verbal fluency test; WCST: Wisconsin card sorting test; WHO-Five WBI: WHO-five wellbeing index.