Study designs of evaluations included in the review
Randomised controlled trials (RCTs) were eligible for inclusion in the review.
Specific interventions included in the review
Studies evaluating spinal manipulative therapy were eligible for inclusion. The studies included in the review compared manipulative therapy with alternative therapies including one or more of the following: exercise, laser therapy, deep friction massage and no treatment.
Participants included in the review
Studies including patients with cervicogenic headache, diagnosed according to the Classification of Headache Disorders of the International Headache Society or the diagnostic criteria of Sjaastad et al., were eligible for inclusion in the review.
Outcomes assessed in the review
Studies measuring headache intensity, frequency and/or duration were eligible for inclusion in the review.
How were decisions on the relevance of primary studies made?
The authors did not state how the papers were selected for the review, or how many reviewers performed the selection.