Study designs of evaluations included in the review
Case series, cohort designs and randomised controlled trials (RCTs) were included. Single case studies were excluded.
Specific interventions included in the review
Spinal manipulation. The number and duration of treatment sessions varied.
'Control' interventions included no treatment, mobilisation, ice and amitriptyline.
Participants included in the review
Headache sufferers. These are divided into two subgroups: people with tension-type headaches (vascular and non-vascular) and those with migraine-type. One study included people with post-traumatic headache.
Outcomes assessed in the review
The individual studies reported a diverse range of outcomes including: frequency, duration and severity of headaches (assessed in some cases by use of a headache diary); accompanying symptoms such as nausea, dizziness, tinnitus or ear pain, aura, visual disturbances; regional and segmental ranges of motion; and analgesic use.
How were decisions on the relevance of primary studies made?
The author does not state how the papers were selected for the review, or how many of the reviewers performed the selection.