Neural Response to Reward in Young Men with Cannabis Use Disorders

Abstract

Cannabis is one of the most widely used drugs, especially among adolescents. While studies with adults have indicated that cannabis use disorders influence reward-related brain function by attenuating responding in the striatum, little is known about neural response to reward in younger cannabis users, who are still undergoing brain development and who have initiated use relatively recently. We tested the hypothesis that cannabis use disorders would be associated with altered response to monetary reward. Young men (M age= 20 years; 55% European American, 45% African American) with current or recent cannabis abuse or dependence (n=12) or with no history of psychiatric disorders (n=39) participated in a functional magnetic resonance imaging study using a guessing task that includes anticipation and receipt of monetary reward. Factorial models examined group and condition effects on neural response in two regions in reward circuitry: the ventral striatum and the medial prefrontal cortex (mPFC). Young men with cannabis use disorders exhibited greater response to reward anticipation in the putamen and in BA32 than did comparison men (105 voxels, t= 4.73, pFWE <0.05, Talairach coordinates: -15, 4, 4; 400 voxels, t= 5.28, pFWE <0.05; -8, 20, 32, respectively). Additional analyses will consider frequency, quantity, and onset of use. These results indicate that in young adults, cannabis use disorders may be associated with greater neural responding in reward-related brain areas rather than decreased responding. Accordingly, these findings raise questions about the influence of development and cannabis exposure in reward function.