Effects of Smoked Marijuana on Risk Taking and Decision Making Tasks

Acute Effects of Smoked Marijuana on Decision Making, as Assessed by a Modified Gambling Task, in Experienced Marijuana Users

The purpose of this study is to investigate the effects of smoked marijuana on both risk taking and decision making tasks.

Cannabis abuse and dependence are the most prevalent drug use disorders in the United States (Compton et al., 2004), yet little is known about the factors contributing to successful marijuana treatment. Previously, we have shown that cognitive impairments in patients treated for substance disorders are associated with premature treatment dropout. However, little is known about whether such impairments are the result of drug use per se. The objective of this within-subject study is to determine whether decision-making and risk-taking are affected by acute cannabis intoxication. The Balloon Analogue Risk Task (BART; Lejuez et al. 2002) assesses decision making in a context of increasing risk, and the Iowa Gambling Task (IGT; Bechara et al. 1994) tests the ability to balance immediate rewards against long-term negative consequences; both tasks have strong face validity for evaluating cognitive deficits that may contribute to poor treatment outcome. Research volunteers will be current marijuana smokers. Each will participate in three, 4-hour outpatient sessions in the Substance Use Research Center (SURC) in the Division of Substance Abuse at NYSPI. They will smoke a different strength marijuana cigarette (0.0, 1.98, 3.9% THC) in each session in counter-balanced order. After baseline data have been collected (risk taking and decision making behaviors, heart rate, blood pressure, mood scales, exhaled carbon monoxide), participants will take 3-6 puffs, 5 seconds in duration, from a National Institute on Drug Abuse (NIDA) marijuana cigarette. After smoking, we will repeatedly re-assess risk taking and decision making abilities with the BART and IGT. We will also measure subjective mood ratings, heart rate and blood pressure repeatedly for 180 minutes following smoking. This study is the first controlled investigation of the effects of smoked marijuana on both risk taking and decision making tasks. The data obtained will be used to guide treatment development for marijuana use disorders.

In this randomized, placebo-controlled study, every participant received all 3 treatment interventions in randomized order. Inactive marijuana (0% THC) served as a placebo comparator. Participants received an inactive marijuana cigarette (0% THC; provided by NIDA) in 1 of the 3 outpatient sessions in randomized order.

In this randomized, placebo-controlled study, every participant received all 3 treatment interventions in randomized order. Participants received active marijuana cigarettes (1.8, or 3.9% THC; provided by NIDA) over 2 of 3 outpatient sessions in randomized order.

Placebo marijuana was administered using a cued-smoking procedure, which produces reliable increases in heart-rate and plasma THC. All marijuana cigarettes were administered in a double-blind fashion.

Active marijuana (1.8 % THC) was administered using a cued-smoking procedure, which produces reliable increases in heart-rate and plasma THC. All marijuana cigarettes were administered in a double-blind fashion.

Active marijuana (3.9%) was administered using a cued-smoking procedure, which produces reliable increases in heart-rate and plasma THC. All marijuana cigarettes were administered in a double-blind fashion.

A modified version of the Gambling Task (Bechara et al., 1994) was used. Four decks of cards (A-D) were displayed on a computer screen. Volunteers were told that the objective of the game was to win as much money as possible. They were also told that the game entailed a series of card selections from any of the decks, one card at a time, and that they should select cards until instructed to stop. The task was stopped after 100 card selections or after 5 min had elapsed. Data indicate change from baseline in mean number of cards selected from advantageous decks minus number of cards selected from disadvantageous decks as a function of drug condition. Higher numbers indicate better decision making regarding advantageous cards. Planned comparisons using single degrees of freedom, generated by a two-tailed repeated measures analysis of variance (ANOVA), were used to examine the effects of THC concentration (0% vs. 1.8%, 0% vs. 3.9%, and 1.8% vs. 3.9%) on task performance.

Inclusion Criteria: Current marijuana use 21-45 years of age Practicing an effective form of birth control Not seeking treatment for marijuana use Exclusion Criteria: Current, repeated illicit drug use other than marijuana Presence of significant medical illness (e.g., diabetes, cardiovascular disease, hypertension) Laboratory tests outside normal limits that are clinically unacceptable to the study physician (BP > 140/90; hematocrit < 34 for women, < 36 for men) Significant adverse reaction to marijuana Current parole or probation Pregnancy or current lactation Recent history of significant violent behavior Major current Axis I psychopathology (e.g., mood disorder with functional impairment or suicide risk, anxiety disorder, schizophrenia History of heart disease Current use of any over-the-counter or prescription medication from which the volunteer cannot be withdrawn