Objective: To investigate the question whether or not spinal manipulation is associated with specific treatment effects.
Methods: Literature searches were carried out in Medline, Embase and The Cochrane Library. All sham-controlled trials of spinal manipulation were considered.
Results: Seven such studies were located. Their methodological quality was variable but three trials adhered to the highest standards of scientific rigour. Collectively these data do not show therapeutic effects beyond placebo. In particular, the three most rigorous studies were negative.
Conclusion: The few sham-controlled trials that do exist show that this methodology is, in principle, applicable also to spinal manipulation. The results available to date suggest that the therapeutic success of spinal manipulation is largely due to a placebo effect.