Bernaerts 2020.

Study characteristics
Methods	4‐week parallel trial of oxytocin versus placebo
Participants	Inclusion criteria: diagnosis of ASD based on DSM‐4‐TR male aged 18‐35 years Exclusion criteria: any neurological or genetic disorder, or contraindication for MRI Location/ setting: autism centre at the Leuven University Hospital, Belgium Sample size: oxytocin 22; placebo 18 Reasons for dropouts/withdrawal: the reason was not provided for the 1 participant from the placebo group who was not included in the analysis. Mean IQ: approx 103 for both groups Mean age: 24.5 years Gender: details not provided Baseline ABC‐I or other BoC scale: oxytocin: WHO QoL 82.91 (14.04); placebo 85.24 (9.63) Concomitant medications: 6/22 in oxytocin group were on psychostimulants. Other medications included antidepressants, aripiprazole, unspecified antipsychotics and carbamazepine (Tegretol). 2/18 in placebo group were on psychostimulants. Other medications included antidepressants, and risperidone. Previous medications ‐ not reported
Interventions	Intervention (oxytocin): 4 weeks of intranasal oxytocin (24 IU), once daily in the morning Comparator (placebo): nasal spray for 4 weeks, once daily in the morning Timing of outcome assessments: baseline and endpoint (4 weeks)
Outcomes	Primary outcomes: AEs Secondary outcomes: QoL (change from baseline) measured using the WHO QoL scale (WHO 1998)
Notes	Study start date: April 2015 Study end date: December 2016 Funding: this research was supported by the Branco Weiss fellowship of the Society in Science ‐ ETH Zurich and by grants from the Flanders Fund for Scientific Research (FWO projects KAN 1506716N, KAN 1521313N, G040112 & G079017N). Conflicts of interest: S.B. is supported by a fund of the Marguerite‐Marie Delacroix foundation. Trial registry: European Clinical Trial Registry (Eudract 2014‐000586‐45)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomised order
Allocation concealment (selection bias)	Unclear risk	Details regarding allocation concealment not provided
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Except for the manager of randomisation, all research staff conducting the trial, participants, and their parents and/or partners were blinded to treatment allocation.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Except for the manager of randomisation, all research staff conducting the trial, participants, and their parents and/or partners were blinded to treatment allocation.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Data were analysed using an ITT format with LOCF to replace missing data
Selective reporting (reporting bias)	Low risk	All primary and secondary outcomes listed on clinical registry were reported.
Other bias	Low risk	No other obvious sources of bias identified