Ward 1991.

Methods	R, DB, AC, PC, cross‐over study 4 episodes treated, each with 1 of 4 study interventions
Participants	Non‐migrainous headaches, ≥ 6/month of > mild intensity n = 60 completed (53 for efficacy) M 17, F 36 Mean age 37 years (range 20‐60 years) Baseline pain ≥ 48/100
Interventions	Paracetamol 648 mg Paracetamol 648 mg + caffeine 65 mg Paracetamol 648 mg + caffeine 130 mg Caffeine 65 mg Caffeine 130 mg Placebo
Outcomes	PI: 10 cm VAS over 2 h Profile of mood states over 2 h
Notes	Oxford Quality Score: R1, DB1, W0
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Details of randomisation method not reported
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	No details reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	No details reported
Incomplete outcome data (attrition bias) All outcomes	High risk	Completer analysis
Size	Unclear risk	50‐200 participants per treatment arm (≤ 53)

AC: active controlled; AE: adverse event; BOCF: baseline observation carried forward; DB: double‐blind; DD: double‐dummy; Excl: exclusions; F: female; h: hour; HR: headache relief; ICD: International Classification of Diseases; IHS: International Headache Society; ITT: intention to treat; M: male; mod: moderate; N: number of participants in study; n: number of participants in treatment arm; NSAID: nonsteroidal anti‐inflammatory drug; OTC: over‐the‐counter; PC: placebo controlled; PF: pain‐free: PI: pain intensity; PID: pain intensity difference; PP: per protocol; PR: pain relief; R: randomised; SD: standard deviation; SPID: summed pain intensity difference; TTH: tension‐type headache; VAS: visual analogue scale; VRS: verbal rating scale; W: withdrawals; WOCF: worst observation carried forward.