Balanced placebo design with marijuana: Pharmacological and expectancy effects on impulsivity and risk taking
- First Online:
Marijuana is believed to increase impulsivity and risk taking, but the processes whereby it affects such behaviors are not understood. Indeed, either the pharmacologic effect of delta-9-tetrahydrocannabinol (THC) or the expectancy of receiving it may lead to deficits in cognitive processing and increases in risk taking.
Objectives and methods
We examined the relative effects of expecting to receive active marijuana and the pharmacological drug effects using a balanced placebo design. Young adult regular marijuana users (N = 136) were randomly assigned into one of four groups in a two × two instructional set (Told THC vs. Told no THC) by drug administration (smoked marijuana with 2.8 % THC vs. placebo) design. Dependent measures included subjective intoxication, behavioral impulsivity, and decision-making related to risky behaviors.
Active THC, regardless of expectancy, impaired inhibition on the Stop Signal and Stroop Color-Word tasks. Expectancy of having smoked THC, regardless of active drug, decreased impulsive decision-making on a delay discounting task among participants reporting no deception and increased perception of sexual risk among women, consistent with a compensatory effect. Expectancy of smoking THC in combination with active THC increased negative perceptions from risky alcohol use. Active drug and expectancy independently increased subjective intoxication.
Results highlight the importance of marijuana expectancy effects as users believing they are smoking marijuana may compensate for expected intoxication effects when engaged in deliberate decision-making by making less impulsive and risky decisions. Effects of marijuana on impulsive disinhibition, by contrast, reflect direct pharmacologic effects for which participants did not compensate.
KeywordsTHC Cannabis Expectancy Impulsivity Inhibition Risk taking Sexual risk
- Dennis ML, Funk R, Harrington Godley S, Godley MD, Waldron H (2004) Cross-validation of the alcohol and cannabis use measures in the Global Appraisal of Individual Needs (Gain) and Timeline Followback (TLFB; Form 90) among adolescents in substance abuse treatment. Addiction 99(Suppl 2):120–128. doi:10.1111/j.1360-0443.2004.00859.x PubMedCrossRefGoogle Scholar
- Marlatt GA, Rohsenow D J (1980) Cognitive processes in alcohol use: expectancy and the balanced placebo design. Advances in Substance Abuse: Behavioral and Biological Research, Greenwich, CT: JAI Press 159-199.Google Scholar
- Martin W, Sloan J, Sapira J, Jasinski D (1971) Physiologic, subjective, and behavioral effects of amphetamine, methamphetamine, ephedrine, phenmetrazine, and methylphenindate in man. Clinical Pharmacological Therapy 12:245–258Google Scholar
- Sexton BF, Tunbridge RJ, Brook-Carter N, Jackson PG (2000) The influence of cannabis on driving. UK DETR Road Safety Research Report ISSN 0968-4107 Retrieved 11-24-2004 from: www.csdporg/research/TRL477pdf
- Stroop JR (1935) Studies of interference in serial verbal reactions. Journal of Experimental Psychology: Applied 12:242–248Google Scholar
- Vogel-Sprott M, Fillmore MT (1999) Expectancy and behavioral effects of socially used drugs. How expectancies shape experience. Washington, DC: American Psychological Association. Kirsch, E. I. (Ed.): 215–232. doi:10.1037/10332-009
- Weinstein A, Brickner O, Lerman H, Greemland M, Bloch M, Lester H et al (2008) A study investigating the acute dose-response effects of 13 mg and 17 mg delta 9-tetrahydrocannabinol on cognitive-motor skills, subjective and autonomic measures in regular users of marijuana. J Psychopharmacol 22:441–451. doi:10.1177/0269881108088194 PubMedCrossRefGoogle Scholar