How Impulsive Are Marijuana Smokers?
While impulsivity is certainly a reality for marijuana users, it is less clear how much of the impulsivity is due to marijuana use, and how much can be explained by the user’s anticipation of impulsivity following marijuana use. A recent study examined the difference between marijuana use and expectancy and the effects on impulsivity and risk behaviors (Metrik et al., 2012).
The researchers enrolled 136 marijuana users in the study through advertisements in newspapers, fliers and on social media sites. Each individual was assigned to one of four groups:
- Participants were told they were receiving THC, and they received THC.
- Participants were told they were receiving a placebo, and they received the placebo.
- Participants were told they were receiving THC, but they received the placebo.
- Participants were told they were receiving a placebo, but they received THC.
The participants were given either an active marijuana cigarette containing THC or a placebo cigarette without THC.
The participants were also required to complete exercises, which included impulse disinhibition tasks including the Stroop Color-Word task. In the Stroop task, the participants were measured according to suppressing their instinct to respond impulsively, such as by reacting incorrectly to the word “blue” written in a green font. The tasks also included measures of impulsive decision-making that involved waiting for larger monetary rewards or immediately choosing smaller rewards.
After waiting 90 minutes following smoking the marijuana or placebo cigarette, participants were then required to complete the exercises again. In addition, participants were asked about their suspicions as to whether they had been given THC.
To measure impulsivity, researchers subtracted the initial score from the post-smoking score. Researchers also used the ARCI-Marijuana scale as a tool to evaluate subjective intoxication.
Only two of the participants who were told they were receiving THC but received the placebo reported being suspicions about the content of the cigarettes. Seven of the participants who were told that they were receiving the placebo but received THC reported their suspicions about the cigarettes’ content.
Those who consumed THC and those who expected that they would consume THC resulted in an increased level of subjective intoxication.
As noted by the researchers, the study results have a number of limitations. The study used computerized exercises to test impulsivity, which may not reflect impulsivity tests that are presented in a real-life setting. In addition, the results may only apply to those who regularly use marijuana, because only regular marijuana-users were invited to participate.