Ref (type)	Population	Outcome, Interventions	Results and statistical analysis	Effect size	Favours
Symptom severity
[18] RCT	41 people with CTTH (diagnostic criteria used were unclear)	Mean general pain (assessed by VAS) 3 months 4.1 with sodium valproate 4.0 with placebo	Reported as not significant P value not reported Non-significant between-group differences were also reported at 1 month (P values not reported)		Not significant
[18] RCT	41 people with CTTH (diagnostic criteria used were unclear)	Mean maximum pain (assessed by VAS) 3 months 5.3 with sodium valproate 5.6 with placebo	Reported as not significant P value not reported Non-significant between-group differences were also reported at 1 month (P values not reported)		Not significant
[18] RCT	41 people with CTTH (diagnostic criteria used were unclear)	Pain frequency (mean number of days with pain per month) 3 months 10.5 with sodium valproate 22.3 with placebo	P <0.05 Significant between-group differences for pain frequency were also observed at 1 month in favour of sodium valproate (12.5 days/month with sodium valproate v 22.5 days/month with placebo, P <0.05)	Effect size not calculated	sodium valproate