Placebo effects of tobacco smoking and other nicotine intake.

Nicotine intake is a necessary but insufficient factor in maintaining tobacco smoking behavior, and nonpharmacological factors associated with smoking play a key role. Some of these factors may influence smoking behavior by eliciting placebo effects, or responses related specifically to the belief that one is consuming a drug. Greater knowledge of placebo effects of smoking would improve our understanding of factors that maintain smoking behavior, thereby aiding efforts to develop treatments to counter the influence of these factors. In addition, better understanding of placebo effects from other means of nicotine intake could help determine mechanisms of the therapeutic actions of nicotine replacement therapy, perhaps enhancing its efficacy in smoking cessation. Placebo effects of smoking or other nicotine intake have received little research attention. In this review, we first discuss common terms and methods of placebo research, especially the balanced-placebo design. We then examine the limited research directly assessing placebo effects of smoking and other nicotine intake, namely studies that manipulated instructions to subjects about the drug content of an ingested substance. Finally, we examine other studies relevant to gauging the likely magnitude of placebo smoking effects. In an effort to encourage more research on these placebo effects, we pay substantial attention to future directions. Among recommendations are testing the utility of the balanced-placebo design and other rigorously controlled designs, and including multiple measures of placebo effects in addition to self-report. Future research also should explore the moderating influences of the environmental context and of individual difference factors on placebo effects of smoking and other nicotine intake.