Tannock 1993.

Study characteristics
Methods	Cross‐over trial with 3 interventions: LD‐MPH HD‐MPH placebo Phases Each child in ADHD group participated in a 6‐day medication trial, consisting of six 3‐h test sessions Each child was tested on 2 separate occasions when given placebo, LD‐MPH (0.3 mg/kg) and HD‐MPH (1.0 mg/kg) in a randomly assigned counterbalanced sequence
Participants	Number of participants screened: not stated Number of participants included: 22 (and 16 healthy controls) Number of participants followed up: 22 (21 boys, 1 girl) Number of withdrawals: 0 Diagnosis of ADHD: DSM‐III (subtype not stated) Age: mean 9.4 years (range not stated) IQ: mean 105.5 (SD 11.3) MPH‐naive: not clear: "Thus all these children would have received a trial with psychostimulants independently of this study"; "8 children had been receiving stimulant medication prior to this study") Ethnicity: not stated Country: Canada Setting: outpatient clinic Comorbidity: 55%; oppositional disorder (n = 5), CD (n = 3), emotional disorder as well as oppositional or CD (n = 4), major depression (n = 2), avoidant disorder (n = 1), separation anxiety disorder (n = 1) and learning disorder (n = 6) Comedication: not clear Other sociodemographics: none Inclusion criteria Confirmed diagnosis of ADHD: child demonstrated ≥ 3 symptoms of inattentiveness, 3 of impulsiveness and 2 of hyperactivity, with a history of these symptoms before 6 years of age, based on diagnostic interview Diagnosis was made if the child received a Rutter B total score ≥ 9 and fulfilled any 2 of the following criteria: score ≥ 15 on the Conners' Abbreviated Teacher Questionnaire; ≥ 4 inattentive, 4 impulsive and 3 hyperactivity symptoms on the SNAP; or score of 5 or 6 on the Rutter‐B hyperactivity factor Exclusion criteria WISC‐R: score < 80 with psychosis, or with any major neurological, physical or sensory impairment
Interventions	Participants were randomly assigned to 1 of 6 possible drug condition orders of (dose not stated) MPH and placebo Mean MPH dosage: not stated Administration schedule: 6 separate medication administrations: 2 placebo, 2 LD (0.3 mg/kg) and 2 HD (1.0 mg/kg). First 3 test sessions were ordered randomly, then were ordered repeatedly for last 3 sessions: daily for 6 days Duration of each medication condition: 3 h Washout before trial initiation: 48 h Medication‐free period between interventions: not clear Titration period: none Treatment compliance: "Medication was administered by project staff"
Outcomes	Non‐serious AEs BP and pulse readings: before and 1 h after ingestion Reduced social responsivity: during each test session, observer Intense concentration: during each test session, observer Stereotypy: during each test session, observer
Notes	Sample calculation: no Ethics approval: not stated Key conclusions of trial authors Results indicate that only high‐dose treatment had a specific effect on focused attention, and this effect was delayed relative to the more salient but non‐specific effects on overall efficiency of information processing Task performance at high dose was related to concurrent clinical manifestations of intense concentration, but no evidence suggested that MPH produced overfocusing Exclusion of MPH non‐responders/children who have previously experienced AEs while taking MPH before randomisation: unclear Withdrawals due to AEs: no Funding source: Canadian Psychiatric Research Foundation and the Medical Research Council of Canada. Email correspondence with trial authors: April 2014. Emailed trial authors twice for supplemental information/data but have received no response
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Low risk	Double‐blind, placebo‐controlled, within‐participant design was used ...randomly assigned, counterbalanced sequence. Medications were prepared individually for each child and were packaged in coloured gelatin capsules to avoid detection of dose and taste
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Double‐blind, placebo‐controlled, within‐participant design was used ...randomly assigned, counterbalanced sequence. Medications were prepared individually for each child and were packaged in coloured gelatin capsules to avoid detection of dose and taste
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Unclear
Incomplete outcome data (attrition bias) All outcomes	Low risk	No withdrawals were noted Selection bias (e.g. titration before randomisation → exclusion): no
Selective reporting (reporting bias)	Low risk	No indication of selective reporting, all outcomes reported