If you give people a placebo and tell them it’s a painkiller costing $2.50, they can withstand painful shocks better than if they’re told the pill costs a dime. Patient characteristics are shown in the Table. In the regular-price group, 85.4% (95% confidence interval [CI], 74.6%-96.2%) of the participants experienced a mean pain reduction after taking the pill, vs 61.0% (95% CI, 46.1%-75.9%) in the low-price (discounted) group (P = .02). Similar results occurred when analyzing only the 50% most painful shocks for each participant (80.5% [95% CI, 68.3%-92.6%] vs 56.1% [95% CI, 40.9%-71.3%], respectively; P = .03).

Source: