NCT02039908.

Study characteristics
Methods	A 4‐week cross‐over trial with 2 arms: 2 weeks of MPH 2 weeks of placebo Phases: 3 phases (titration phase, double‐blind cross‐over phase, and 10‐month medication‐holiday‐trial)
Participants	Number of participants screened: not stated Number of participants included: 267 (213 boys, 54 girls) Number of participants followed‐up: 248 Number of withdrawals: 19 Diagnosis of ADHD: DSM‐IV (subtype not stated) Age: mean not reported (range 6‐12 years) IQ: > 80 MPH‐naive: not stated Ethnicity: Hispanic or Latino (n = 224, 83.9%), not Hispanic or Latino (n = 43, 16.1%). Race: Asian (n = 2, 0.7%), black or African American (n = 22, 8.2%), white (n = 237, 88.8), mixed race (n = 6, 2.2%) Country: USA Setting: outpatient, summer treatment programme Comorbidity: some were exclusion criteria; ODD, CD or a mood or anxiety disorder not requiring psychotropic medication were allowed Comedication: no psychotropic comedication allowed Additional sociodemographics: none Inclusion criteria Aged 6‐12 years old Diagnosis of ADHD according to DSM‐IV‐TR Full scale IQ > 80 Exclusion criteria Psychotropic medications for conditions other than ADHD Active medical or psychiatric conditions that could be worsened by stimulants Diagnosis of Autism or Asperger's Disorder Documented intolerance for MPH or failed trial of OROS‐MPH
Interventions	Participants were randomly assigned to receive either 13 days of optimal‐dose MPH then a 2‐day medication/placebo probe followed by 13 days of placebo, or 13 days of placebo then a 2‐day medication/placebo probe followed by 13 days of optimal‐dose MPH Number randomised to each group: 129 medication first, 138 placebo first Mean medication dosage: not stated Administration schedule: not stated Duration of each medication: 13 days plus probe Washout before trial initiation: not stated Medication‐free period between interventions: yes, 2 days Titration period: 9 days during the first 2 weeks of the summer treatment camp, placebo‐controlled assessments of up to 4 different OROS‐MPH doses (18 mg, 27 mg, 36 mg, 54 mg; max dose not to exceed 2 mg/kg/d) will be conducted to establish each child’s optimal dose Treatment compliance: not stated
Outcomes	Serious AEs Mortality (none), assessed by spontaneous reporting Hospitalisation, assessed by spontaneous reporting Non‐serious AEs Pittsburgh Side Effect Rating Scale. Assesed "daily for the first 2 weeks of the summer and weekly for the final 6 weeks of the summer. During Phase 2, side‐effects ratings were completed by parents monthly at medication dispensing visits. daily for the first 2 weeks of the summer and weekly for the final 6 weeks of the summer. During Phase 2, side‐effects ratings were completed by parents monthly at medication dispensing visits." (NCT02039908)
Notes	Sample calculation: not stated Ethics approval: not stated No comments or conclusions Exclusion of MPH non‐responders/children who have previously experienced AEs while taking MPH: yes, titration phase before randomisation Any withdrawals due to AEs: not stated Funding source: Florida International University Email correspondence with trial authors: August and October 2021. We contacted the trial authors for information regarding risk of bias and data through personal email in August and October 2021, but no answer was received.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Nothing stated
Allocation concealment (selection bias)	Unclear risk	Nothing stated
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Mention of blinding, but no mention of method
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Mention of blinding, but no mention of method
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	19 withdrawals, nothing further stated Selection bias (e.g. titration after randomisation → exclusion of MPH non‐responders or placebo responders): no
Selective reporting (reporting bias)	Low risk	All protocol outcomes reported