The Effects of Low Doses of Δ-9 Tetrahydrocannabinol on Reinforcement Processing in the Risky Decision-Making of Young Healthy Adults

Abstract

Research suggests that risky decision-making is sensitive to neuromodulatory influences acting upon corticolimbic circuitry. However, while other evidence attests to effects of D-9 tetrahydrocannabinol (THC) on the activity of reward pathways, relatively little is known about the possible involvement of cannabinoid activity in risky choice. In this experiment, we examined the effects of a single sublingual 5 mg dose of THC on a test of risky decision-making (requiring choices between simultaneously presented gambles differing in their magnitude of gains, magnitude of losses and the probability with which these outcomes were delivered). Tests of non-normative decision-making involving risk-aversion when deciding between gains and risk-seeking choices when deciding between losses were also included. In all, 15 healthy adults were administered 5 mg THC and placebo in a double-blind, placebo-controlled, within-subject, crossover design. THC had three principal effects relative to placebo: (i) THC reduced choice of gambles with variable gains and losses, but increased choice of gambles with zero-expected value; (ii) THC reduced participants' attention towards losses when the probability of winning was low (and the probability of losing was high); and (iii) THC speeded participants' responses to gambles with large compared to small potential gains. These results suggest that THC mediates specific motivational processes and the processing of reinforcement cues during risky choice, perhaps reflecting altered CB 1 receptor or catecholamine activity within corticolimbic pathways.

Cannabinoids and value-based decision making: Implications for neurodegenerative disorders

“…This contrasts recent PET data showing that in 1-day abstinent heavy marijuana smokers regional blood flow in the ventromedial prefrontal cortex and cerebellum was increased during performance in the Iowa gambling task [114]. In keeping with the aforementioned behavioral findings of altered cost-benefit processing induced by THC [106] or in heavy marijuana users [111], fMRI approaches indicate accompanying reductions in brain activation in regions such as the anterior cingulate cortex, medial frontal cortex and cerebellum, particularly during loss of reward [115,116]. Notably, despite the high densities of cannabinoid CB1 receptors in basal ganglia structures in the human brain [19], their involvement and possible differential activation by exogenous cannabinoids in risky decision making is not as pronounced as that of prefrontal cortical regions from the current neuroimaging work.…”

“…Thus, under conditions with uncertainty about the likelihood of punishment, activation of cannabinoid CB1 receptors influences the sensitivity to reinforcement as well as punishment. These findings have been further substantiated by several recent studies implementing neurocognitive risk-based decision making tasks such as the Iowa Gambling Task and related gambling tasks in healthy volunteers and marijuana users [106,107]. Briefly, in the Iowa Gambling Task originally developed by Bechara and coworkers [108] subjects have to make a cost-benefit assessment based on their decisions and are able to draw cards from one of four decks to obtain monetary reward.…”

“…Heavy marijuana use has been associated with an increased preference for risky decisions leading to monetary loss [109] and a positive correlation has been reported between the magnitude of use and risky decision making [107], although comparable effects of THC on decision making are not consistently observed in frequent marijuana users [110]. In line with the former findings, in a related gambling task, THC challenges in healthy volunteers increased the choice of decisions with a zero-expected value and altered aspects of processing decisions, for instance by reduced attention towards losses and faster reaction times related to gambles with large gains [106]. This has recently been further confirmed using computational models of the Iowa Gambling Task showing that heavy cannabis users are indifferent to loss magnitude and perceived both small and large losses as equal minor negative outcomes [111].…”

Alterações na percepção emocional em usuários de cannabis

“…Embora a literatura esteja repleta de estudos sobre o efeito do uso de cannabis na atenção, memória operacional e funções executivas (Chang et al, 2006;Jager et al, 2006;Kanayama et al, 2004, Solowij et al, 2002, aprendizagem associativa (Nestor et al, 2008) e decisão (Rogers et al, 2007;Whitlow et al, 2004), ainda há poucos estudos sobre o efeito dessa substância na percepção emocional, especificamente, e emoção como um todo.…”

Cannabis and cognition: short- and long-term effects

“…We also do not know whether, or how, regular users may develop compensatory strategies during acute intoxication to facilitate performance that might otherwise be impaired. For example, in a risky decision-making task, Rogers et al (2007) showed a reduction of risky behavior following lowdose sublingual administration of THC to healthy young adults (not regular cannabis users), with an adoption of more cautious cognitive strategies to compensate for the perceived disruption of effective decision making by cannabis. Thus regular users, due to their greater experience with cannabis, might be more likely to develop alternate compensatory strategies.…”