Pelham 1992.

Methods	Design: three group, multi‐period cross‐over trial (number of periods NS) Purpose: examine the perception of what influenced mood and behaviour (causal attribution) in boys treated for attention deficit hyperactivity disorder by methylphenidate or placebo
Participants	Patients: boys with attention deficit hyperactivity disorder attending a summer camp Baseline comparability: not relevant
Interventions	Placebo: tablet with no methylphenidate Untreated: no tablet Experimental: tablet with methylphenidate (Co‐intervention: ‐summer camp treatment program (behavioural therapy principles) ‐same boys also participated in trials with other drugs on days not included in the present study)
Outcomes	Behaviour rating scales, including ratings of "Did you have a good day?" Attribution rating scales (what the children themselves thought influenced behaviour or mood) Mood/self‐esteem rating scales Forced‐Choice Questions
Notes	The outcome data was not available from the first period only, and was calculated as deriving from a parallel group trial.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Unclear risk	NS
Allocation concealment?	Unclear risk	NS
Blinding? Treatment provider	Low risk	'... designed to examine ADHD boys' causal attributions in a double‐blind, within‐subject, placebo‐controlled medication trial'
Blinding? Outcome assessor	Unclear risk	Not relevant as patient reported outcome
Incomplete outcome data addressed? All outcomes	High risk	Drop‐out > 15% or NS
Free of selective reporting?	Unclear risk	No protocol available
Free of other bias?	Low risk
No signs of variance inequality or skewness?	Low risk	No variance inequality (F‐test not statistically significant) and no skewness (1.64 standard deviations does not exceed the mean)
Trial size > 49?	Low risk	N = 76
Clearly concealed allocation + trial size > 49 + drop‐out max 15%	High risk	Drop‐out > 15% or NS