“…In all studies, participants were allowed to use abortive (acute) medication, regardless of the intervention allocation. The most common outcome measured was headache intensity via the visual analogue scale (VAS) (24,26,30–34), the numerical rating scale (NRS) (25,27,29,35–38), the verbal rating scale (28) or the 3-point severity index of the headache disability inventory (HDI) (39,40). Headache frequency was measured via a headache diary (1 week to 3 months) (23,25,26,28–32,35,36,38), the 3-point scale of the HDI (39,40), a 4-point scale (33) or a 5-point Likert scale (27).…”