Most clinical trials that examine the efficacy of preventive treatments in chronic migraine in adults adhere to the recommendations of the 2008 International Headache Society (IHS); however, adherence to migraine-specific recommendations was lower. This according to a review in which researchers used a 13-item scoring system enlisting essential recommendations adapted from the guidelines to evaluate trial quality. They found:

• Of 3,352 retrieved records, 16 were included in the analysis.
• The median score was 6.5 (range 2‒13).
• All trials were randomized, with most (81.25%) placebo-controlled and double-blinded (87.5%).
• Adherence was lowest on: a priori definition of outcomes (31.25%), primary endpoint definition (37.5%), and trial registration (37.5%).