“…Almost all studies performed a comparison against no treatment, treatment as usual (TaU) or waitlist [ 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ], with the exception of one study that was based on a single group [ 37 ]. Headache frequency was used as an outcome of treatment in almost all studies [ 20 , 21 , 22 , 24 , 25 , 26 , 34 , 35 , 36 , 37 ], with the variation over time being significant in the majority of the studies [ 21 , 22 , 25 , 26 , 34 , 35 , 36 , 37 ].…”