Analgesic effects of treatments for non-specific low back pain: a meta-analysis of placebo-controlled randomized trials

Objective. Estimates of treatment effects reported in placebo-controlled randomized trials are less subject to bias than those estimates provided by other study designs. The objective of this meta-analysis was to estimate the analgesic effects of treatments for non-specific low back pain reported in placebo-controlled randomized trials. Methods. Medline, Embase, Cinahl, PsychInfo and Cochrane Central Register of Controlled Trials databases were searched for eligible trials from earliest records to November 2006. Continuous pain outcomes were converted to a common 0100 scale and pooled using a random effects model. Results. A total of 76 trials reporting on 34 treatments were included. Fifty percent of the investigated treatments had statistically significant effects, but for most the effects were small or moderate: 47 had point estimates of effects of 10 points on the 100-point scale, 38 had point estimates from 10 to 20 points and 15 had point estimates of 20 points. Treatments reported to have large effects (20 points) had been investigated only in a single trial. Conclusions. This meta-analysis revealed that the analgesic effects of many treatments for non-specific low back pain are small and that they do not differ in populations with acute or chronic symptoms.