Johnston 1988.

Study characteristics
Methods	2‐week cross‐over trial with 3 interventions: MPH placebo ER‐MPH (we do not report on this group here) Phases: to define rebound effects in 21 boys 4‐10 years of age, with a DSM‐III diagnosis of ADD and treated with MPH some days, and placebo other days
Participants	Number of participants screened: not stated Number of participants included: 21 Number of participants followed up: 21 (21 boys, 0 girls) Number of withdrawals: 0 Diagnosis of ADD: DSM‐III‐R (subtype not stated) Age: mean 7 years 7 months (range 4‐10 years) IQ: mean 101 (range 79‐120) MPH‐naive: not stated Ethnicity: not stated Country: USA Setting: outpatient clinic (summer treatment programme) Comorbidity: CD (n = 2), ODD (n = 17), learning disability (n = 9) Comedication: not stated Other sociodemographics: none Inclusion criteria DSM‐III‐R diagnosis of ADD Exclusion criteria Not stated
Interventions	Participants were randomly assigned to different drug condition orders of: 0.3 mg/kg MPH, 0.6 mg/kg MPH, 20 mg ER‐MPH, or placebo. Number randomised to each group: 0.3 mg/kg MPH twice daily: 21, 0.6 mg/kg MPH twice daily: 16 of the same 21 participants who received 0.3 mg/kg MPH, 20 mg ER‐MPH: 8, placebo, not stated. Within‐participant random sequence, condition varied daily Mean MPH dosage: not stated Administration schedule: twice daily, at breakfast and just before lunch Duration of intervention: 2 weeks. Note: it is not clear for how many days each boy received either of the MPH doses or placebo Washout before trial initiation: not stated Medication‐free period between interventions: not stated Titration period: not stated Treatment compliance: not stated
Outcomes	ADHD symptoms Modified Conners' Scale Parent, daily, and Teacher‐rated ACRS, 2‐3 ratings per treatment condition. Daily reports of social and academic behaviour. Not stated who did the rating for these reports SNAP, teacher‐rated Abbreviated CRS IOWA CTRS Non‐serious AEs Rebound/Modified Conners' Scale, Parent, for rebound effect assessment Specific Behaviour Ratings by parent (5, specific individual problem behaviours, rated every night)
Notes	Sample calculation: none Ethics approval: no information Comment from review authors Non‐validated endpoints used. No definition (defined cut‐off score on scales) of what the authors considered to be ‘rebound’ Exclusion of MPH non‐responders/children who have previously experienced AEs while taking MPH before randomisation: not stated Any withdrawals due to AEs: no Funding source: not declared Email correspondence with trial authors: emailed trial authors to request additional information. Also asked whether this trial includes the Pelham 1989 reference. No answer from trial author, so we extracted data as from 2 different studies
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Order of drug condition for each child was randomly assigned over days
Allocation concealment (selection bias)	Unclear risk	Not stated
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Child, parent, teacher and programme counsellors were blinded to the condition. Active medication and placebo were disguised in gelatin capsules and pre‐packaged in individually dated envelopes
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not stated
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not stated Selection bias (e.g. titration after randomisation → exclusion of MPH non‐responders or placebo responders): no
Selective reporting (reporting bias)	Unclear risk	No protocol available