American placebo: New analysis of chronic pain drug trials shows increasing placebo responses over time, in the US only

Rising placebo responses may play a part in the increasingly high failure rate for clinical trials of drugs designed to control chronic pain caused by nerve damage, suggests a new report. Surprisingly, however, the analysis of clinical trials conducted since 1990 found that the increase in placebo responses occurred only in trials conducted wholly in the US; trials conducted in Europe or Asia showed no changes in placebo responses over that period.