Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Headache frequency
[22] Systematic review	675 people with CTTH 7 RCTs in this analysis	Headache frequency (mean headaches/month) 56–120 days with botulinum toxin A with placebo Absolute results not reported	MD –1.43 95% CI –3.13 to +0.27 Heterogeneity: I2 = 61.5%; P = 0.02 See Further information on studies		Not significant
[22] Systematic review	447 people with CTTH 3 RCTs in this analysis	Proportion of people with 50% reduction in headaches per month 53/320 (17%) with botulinum toxin A 23/122 (19%) with placebo	RR 1.00 95% CI 0.57 to 1.76		Not significant