Table 1.

Characteristics of the eight included randomised controlled trials evaluating the effect of melatonin in children and adolescents with idiopathic chronic insomnia.

Author, year, country, trial registration	Demographics sex (male/female) age (provided as range or mean, SD)	Design and funding	Intervention (s)	Comparison	Duration	Outcomes of interest, measurement
Eckerberg, 2012, Sweden57 No protocol identified	n = 21, participants with sleep-onset difficulties Sex: 10/11 Overall age, years: 14–19 Melatonin group (n = 21) Sex: 10/11 Age, years: 14–19 Control (placebo) group (n = 21) Sex: 10/11 Age, years: 14–19	RCT, crossover trial Funding: NATURAL PHARMA International, Stockholm Sweden provided the melatonin and placebo capsules.	Melatonin, 1 mg fast release capsules (5-methoxy-N-acetyltryptamine)	Placebo–capsules	5 weeks	Total sleep time: Sleep diary Sleepiness and fatigue during daytime: Karolinska Sleepiness Scale
Smits, 2001, the Netherlands58 No protocol identified	n = 40, participants with idiopathic chronic sleep-onset insomnia Sex: 27/11 Overall age, years: 6–12 Melatonin group (n = 20) Sex: 11/8 Age, years: 6–12 Control (placebo) group (n = 20) Sex: 16/3 Age, years: 6–12	RCT, single center parallel group, two arms. Funding: The Jan Dekker and dr. Ludgardine Bouwman Foundation and the Dutch Society for Sleep-Wake Research.	Melatonin, 5 mg fast release capsules. Administration at 18:00	Placebo—capsules similar to the ones in intervention group	4 weeks	Total sleep time: Actigraph (Gähwiler Electronics, Hombrechtikon, Switzerland) Sleep onset latency: Actigraph Dropouts: Number of participants
Smits, 2003, the Netherlands59 No protocol identified	n = 62, participants with idiopathic chronic sleep-onset insomnia Sex: 49/13 Overall age, years: 6–12 Melatonin group (n = 27) Sex: 20/7 Age, years: 9.2 (2.1) Control (placebo) group (n = 35) Sex: 29/6 Age, years: 10.1 (1.7)	RCT, single center, parallel group, two arms. Funding: The Jan Dekker and dr. Ludgardine Bouwman Foundation.	Melatonin 5 mg fast release capsules (Duchefa Farma BV, Harlem, the Netherlands). Administration at 19:00	Placebo—capsules similar to the ones in intervention group	4 weeks	Daytime functioning: Funktional status II tool Total sleep time: Sleep log/Actigraph Sleep onset latency: Sleep log/Actigraph Dropouts: Number of participants
Van der Heijden, 2005, the Netherlands60 No protocol identified	n = 110, participants with idiopathic chronic sleep onset insomnia Sex: 76/24 Overall age, years: 6–12 Melatonin group (n = 55) Sex: 31/15 Age, years: 6–9 and 10–13 Control (placebo) group (n = 55) Sex: 45/9 Age, years: 6–9 and 10–13	RCT, single center, parallel group, two arms. Funding: The Dr. Ludgardine Bouwman Foundation.	Melatonin 5 mg fast release capsules (Duchefa Farma BV, Harlem, the Netherlands).	Placebo–capsules similar to the ones in intervention group	4 weeks	Individual patient data of two previously published randomised, placebo-controlled, double blind, clinical trials, using similar methodology (Smits et al., 2001, 2003), were combined. Total sleep time: Actigraph Sleep onset latency: Actigraph
Van Geijlswijk, 2010, the Netherlands61 Title registration: International Standard Randomized Controlled Trial Number Register (ISRCTN20033346).	n = 72, participants with chronic sleep onset insomnia Sex: 30/42 Overall age, years: 6–12 Melatonin groups (n = 53) Sex: 24/29 Age, years: 6–12 Control (placebo) group (n = 17) Sex: 6/11 Age, years: 6–12	RCT, single center, parallel group, four arms. Funding: None mentioned	Melatonin 0.05 or 0.1 or 0.15 mg/kg (supplied by Pharma Nord, Denmark) in the appropriate calculated dosage and microcrystalline cellulose. Administered between 17:30 and 19:30.	Placebo containing only microcrystalline cellulose (Bufa, Haarlem, The Netherlands)	2 weeks	Sleep onset: Actigraph Sleep onset latency: Actigraph Wake-up time: Actigraph Total sleep time: Actigraph
Van Geijlswijk, 2011, the Netherlands62 Trial registration: International Standard Randomized Controlled Trial Number Register (ISRCTN20033346).	n = 59, participants with chronic sleep onset insomnia No sex data available Subgroup a. Age, years: <13 years Subgroup b. Age, years: >13 years Melatonin group (n = 59)	Follow up from the RCT study Van Geijlswijk, 2010 Funding: None mentioned	Long term use of melatonin, mean dose 2.69 mg (min 0.3 mg, max 10 mg)		6 months	Dropouts: Number of participants. Quality of sleep: Children sleep health questionnaire Effects of prolonged use of Melatonin—Puberty development: Tanner score (Tanner Stages standard deviation scores could be determined for 16 boys and 30 girls)
Van Maanen, 2017, the Netherlands63 No protocol identified	n = 54, participants with idiopathic chronic sleep onset insomnia Sex: 33/21. Overall age, years: 7–12 Melatonin group (n = 26) Sex: 17/9 Age, years: 10.01 (1.47) Control (placebo) group (n = 28) Sex: 16/12 Age, years: 10.04 (1.63)	RCT, parallel group, two arms. A third arm received light (30 children) Funding: Pharma Nord sponsored the melatonin and placebo tablets for the study	Melatonin tablets (3 mg. fast release, Pharma Nord) Administration at 19:00.	Placebo–tablets, similar to the ones in intervention group	3–4 weeks	Quality of sleep: Sleep efficacy (%)/AW4 actiwatches (Cambridge Neurotechnology Ltd, Cambridge, UK)–Actigraph Total sleep time: Actigraph Sleep onset latency: Actigraph Wake after sleep onset: Actigraph
Jalilolghadr 2022, Iran64 Trial registration: Iranian Registry of Clinical Trials. IRCT 2015111225008N1.	n = 60, healthy participants with insomnia No sex data available Overall age, years: 7–12 Melatonin group (n = 30) Mean age 9.79 (2.02) Control (placebo) (n = 30) Mean age 9.38 (1.05)	RCT, single center, parallel group, two arms Funding: None	Melatonin tablets (Weber Nature company) containing 3 mg Administration at 19:00	Placebo tablets	4 weeks	Daytime functioning: children's sleep habits questionnaire, daily performance subscale

SD: Standard deviation, RCT: Randomised controlled trial, mg: milligram, kg: kilogram, min: minimum, max: maximum.