TCPR’s Take: These results are differ- ent from some prior studies which showed a benefit of Risperdal in this population. One likely reason is that past studies included a “placebo run-in” phase, in which patients who responded rapidly to placebo were excluded from the double-blind study. This had the effect of minimizing the placebo effect in the main study and increasing the likelihood of a drug vs. placebo difference. These investigators did not include the placebo run-in in order to make the design more similar to clinical practice. These results imply that in aggressive mentally retarded adults, placebo effects are extremely powerful, and perhaps prescribing a multivitamin (with great fanfare and high expectations) is as effective as prescribing an antipsychotic, with far fewer side effects.