Palevitch 1997.

Study characteristics
Methods	Randomised, placebo‐controlled, double‐blind trial. Cross‐over. Withdrawal study
Participants	57 patients aged 9 to 65 years. Migraine diagnosed by medical examination; probably migraine with and without aura, though this is unclear (diagnostic criteria not specified)
Interventions	2 capsules (50 mg) of powdered feverfew daily for 1 month or placebo (dry parsley leaves, Petroselinum crispum) after a 60‐day open‐label phase in which all participants received 100 mg feverfew
Outcomes	Intensity of headache. Severity of nausea and vomiting
Notes	Both groups were treated with feverfew in the preliminary open‐label period for 60 days. No wash‐out period. No mention of migraine history, inclusion criteria or drop‐outs/withdrawals Included participants as young as 9 years old Oxford score: 2/5 (R = 1, B = 1, WD = 0)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Described as randomised but randomisation process not described
Allocation concealment (selection bias)	Unclear risk	Not described
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Described as double‐blind but does not mention who was blinded and how blinding was done
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Drop‐outs not reported
Selective reporting (reporting bias)	High risk	Outcome measures not clearly stated. Important outcome measures like frequency of migraine attacks not included
Other bias	Unclear risk	Unclear risk of bias due to sample size (n = 57)