Reduced Response to Reward in Smokers and Cannabis Users

Abstract

Background: Cannabis is one of the most commonly used illicit drugs. Reduced neural and behavioral reactions to reward have been demonstrated in other forms of addiction, as expressed by reduced mood reactivity and lack of striatal activation to rewards, but this effect has not yet been investigated in cannabis users. Methods: We hypothesized that cannabis users and tobacco smokers would evidence lower positive mood ratings in rewarded conditions than control participants and that this reduction would be greater in cannabis users than in smokers. We examined the influence of reward on mood and performance in a group of regular cannabis users, a group of tobacco smokers and a group of nonsmokers while they performed a spatial recognition task with delayed response that incorporated 3 levels of difficulty. Correct responses were either not reinforced or reinforced with money. We measured the accuracy of reactions, reaction times and mood ratings throughout the trials. Results: Cannabis users rated their mood as significantly worse than the smokers and nonsmokers during the easiest level of the rewarded condition. A significant positive correlation between mood ratings and monetary reward was found in the nonsmokers but not in the cannabis users and smokers. The groups did not differ with regard to task performance. Conclusions: Our results suggest that regular cannabis use affects certain aspects of motivation and that both tobacco smoking and cannabis use lead to similar motivational changes. However, the use of cannabis seems to affect motivation in a stronger way than does tobacco smoking alone.

Seeing through the smoke: Human and animal studies of cannabis use and endocannabinoid signalling in corticolimbic networks

“…Functional imaging revealed that while users did not differ behaviourally from non-users during the initial strategy stage, they displayed reduced activity in the anterior cingulate and medial prefrontal cortices in response to losses (Wesley et al, 2011). Strikingly, neural responses to early IGT losses predicted future improvements in task performance in controls, but not cannabis users, suggesting that impaired decision-making may arise from an insensitivity to losses, consistent with reports that regular and heavy cannabis users show abnormalities in affective and reward processing (Gruber et al, 2009; Martin-Soelch et al, 2009; Nestor et al, 2010). Indeed, computational modelling of IGT performance in cannabis users reveals that these individuals tend to be under-influenced by loss magnitude, treating each loss as a constant and minor negative outcome regardless of the size of the loss (Fridberg et al, 2010; but see Bishara et al, 2009).…”

Poor decision-making by chronic marijuana users is associated with decreased functional responsiveness to negative consequences

“…This may also reflect more general deficits in performance monitoring, as increases have also been observed under conditions where errors are likely to occur (Carter et al, 1998) and during violations of outcome expectancy (Oliveira et al, 2007). These reductions may reflect decreased motivation as a result of experiencing monetary losses (Martin-Soelch et al, 2009; Simoes-Franklin et al, 2009). Differences in motivation did not appear to be a significant contributing factor in the study, however, as all individuals completed the task, and groups did not differ in the number of omitted or “no response” events on the task.…”

Altered Frontal Cortical Volume and Decision Making in Adolescent Cannabis Users

“…A separate line of research has suggested that cannabis use may adversely impact reward systems or drug-related cue salience. For example, a study examining the effect of a reward task on mood in adult cannabis users and non-users found that monetary reward had a positive impact on mood in non-users participating in a spatial recognition task, but had no such effect in cannabis users (Martin-Soelch et al, 2009). Moreover, the prefrontal–accumbens circuit is normally involved in reward processing related to goal-directed behavior and cellular adaptations resulting from repeated drug exposure are thought to critically modify this circuit so that it becomes biased toward drug seeking (Kalivas and Volkow, 2005).…”