Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Headache scores
[16] RCT 3-armed trial	90 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2] In review [11]	Reduction in mean headache score 1 week with amitriptyline 10 mg with placebo Absolute results not reported	P <0.001 Mild reduction in headache scores at week 1 with amitriptyline 10 mg	Effect size not calculated	amitriptyline
[16] RCT 3-armed trial	90 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2] In review [11]	Reduction in mean headache score 2 and 4 weeks with amitriptyline 10 mg with placebo Absolute results not reported	No reduction in headache scores at weeks 2 or 4 with amitriptyline 10 mg
[16] RCT 3-armed trial	90 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2] In review [11]	Reduction in mean headache score 1, 2, and 4 weeks with amitriptyline 25 mg with placebo Absolute results not reported	No difference noted at 1, 2, or 4 weeks with 25 mg dose of amitriptyline
[15] RCT Crossover design 3-armed trial	40 people; diagnosed using IHS criteria[17] In review [10]	Reduction in area under headache curve (AUC) 32 weeks with amitriptyline with placebo Absolute results not reported	P = 0.002 for amitryptiline v placebo Results in 34/40 people (85%) who completed the trial Significant result for combined outcome resulted primarily from significant reductions in duration of headache (P = 0.01), rather than headache intensity (P = 0.12)	Effect size not calculated	amitriptyline
[12] RCT 5-armed trial	203 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2]	Clinically important improvement (50% or more reduction in headache scores) 4 weeks 34/53 (64%) with amitriptyline 14/48 (29%) with placebo	RR 2.19 95% CI 1.35 to 3.57	Moderate effect size	amitriptyline
[12] RCT 5-armed trial	203 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2]	Headache index scores 4 weeks with amitriptyline with placebo Absolute results not reported	MD 0.92 95% CI 0.44 to 1.41	Effect size not calculated	amitriptyline
Headache duration, frequency, or intensity
[10] Systematic review	40 people; diagnosed using IHS criteria[17] Data from 1 RCT	Headache intensity 32 weeks with amitriptyline with placebo Absolute results not reported	SMD +0.06 95% CI –0.42 to +0.53		Not significant
[10] Systematic review	40 people; diagnosed using IHS criteria[17]	Headache duration 32 weeks with amitriptyline with placebo Absolute results not reported	SMD +0.22 95% CI –0.26 to +0.7		Not significant
[14] RCT Crossover design	27 people; diagnosed using IHS criteria[17]	50% reduction in headache frequency or severity with amitriptyline with placebo Absolute results not reported	P <0.001	Effect size not calculated	amitriptyline
[13] RCT 3-armed trial	203 people; diagnosed using Criteria of the Ad Hoc Committee, 1962[2]	50% or more reduction in headache frequency, duration, and intensity with amitriptyline with amitriptyline-N-oxide with placebo Absolute results not reported	Reported as not significant for both amitryptyline and amitriptyline-N-oxide v placebo		Not significant