Modification of placebo effects by means of drugs: Effects of aspirin and placebos on self-rated moods.

How do drugs and placebos interact? As a model experiment, changes in self-rated mood were measured in four treatment groups. The Ss in each group received either aspirin or lactose, plus a placebo liquid described to 5s as being either a "tranquilizer " or an "energizer. " Aspirin had no significant main effect on mood, but did cause significant changes in the placebo effects, adding dimensions of friendly intoxication to the tranquilizer effect and of asocial sobriety to the energizer effect. These results, plus analogous results in other studies, argue that Ss ' expectancies concerning treatment effects should be manipulated in any study of potentially psychoactive drugs. An increasing number of studies suggest that the psychological effect of drugs can be understood only by examining the interaction between the pharmacological effects and the cognitive and affective contexts of drug ingestion. This is true for mild drugs such as caffeine or aspirin, for narcotics, and for power-ful intoxicants such as ethanol or tetrahydro-cannabinol. The focus of the present paper is on effects of aspirin, but discussion will draw on work with a wide range of drugs. In clinical use, aspirin is a reasonably reli-able analgesic with no other noteworthy modes of psychoactivity, although a small minority of persons spontaneously report that aspirin makes them jittery or elevated in mood, while others report using aspirin as a sedative. As an analgesic, aspirin owes much of its value to the fact that it is antiinflammatory; it re-duces the source of some pains. A second mechanism, also peripheral, involves aspirin's blocking the effects of bradykinin on peri-pheral pain receptors (Lim, Guzman, Rod-gers, Goto, Braun, Dickerson, & Engle, 1964). These mechanisms, however, do not account for much of the variability of aspirin's effects in laboratory studies with human Ss.!This study was supported by Grant RD-1372-P