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Effectiveness of a marijuana expectancy manipulation: Piloting the balanced-placebo design for marijuana.

Jane Metrik, Damaris J Rohsenow, Peter M. Monti, John E McGeary, Travis A R Cook, Harriet de Wit, Margaret Haney, Christopher W Kahler

Experimental and Clinical Psychopharmacology August 1, 2009 DOI: 10.1037/a0016502 (opens in new tab)

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Characteristics Pilot study using a 2 x 2 balanced-placebo design Peer reviewed
Sample size 20
Population Marijuana smokers (mean age = 20 years; 25% female)
Dose 2.8% THC
Topics Cannabis
Keywords Humans Placebos Pilot projects Attitude Marijuana smoking Affect Adolescent Adult Female Dronabinol
Key points Expectancy manipulation produced large main effects on ratings of cigarette potency, strength, taste, smell, and satisfaction, and on observed smoking behavior. Pharmacologic effects were particularly evident for self-reported physical reactions to marijuana and for cigarette potency and satisfaction ratings. The authors report that the balanced-placebo design is feasible for marijuana research and that the results are promising for future studies of pharmacology and expectancy.

Abstract

Although alcohol and nicotine administration studies have demonstrated that manipulating subjects' expectancies regarding drug content affects drug response, research with marijuana has not adequately studied drug expectancy effects. The present pilot study was the first to evaluate the credibility and effect of expectancy manipulation on subjective measures and smoking patterns using a marijuana administration balanced-placebo design (BPD). In a 2 x 2 instructional set (told delta-9-tetrahydrocannabinol [THC] vs. told no THC) by drug (smoked marijuana with 2.8% THC vs. placebo) between-subjects design, the authors examined the effect of marijuana expectancy manipulation and the pharmacologic effect on affective and physiologic measures, cigarette ratings, and smoking behavior with 20 marijuana smokers (mean age = 20 years; 25% female). Large main effects of expectancy were found on ratings of cigarette potency, strength, taste, smell, and satisfaction, and observed smoking behavior. Pharmacologic effects were particularly evident for self-reported physical reactions to marijuana and cigarette potency and satisfaction ratings. This study demonstrated the feasibility of the BPD research with marijuana and yielded promising results for future studies examining the independent and combined effects of marijuana pharmacology and expectancies.

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