Young adult cannabis users showed unique activation patterns in the striatum during a social influence task, with reward-region activity when following group choices correlating with the amount of cannabis used.
Read this if you are interested in how cannabis use relates to social decision-making and peer influence in young adults.
Reward-region activation when following peers correlated with cannabis use amount
What the researchers found
Twenty young adult cannabis users and 20 non-users completed a decision-making task while undergoing brain scans. The task measured how viewing other people's choices affected their own decisions.
Cannabis users showed activation in the middle striatum (caudate) when applying social information to their choices, an activation pattern not seen in controls. When cannabis users followed the group's choices rather than going against them, they showed greater activation in the nucleus accumbens, a key reward region. This reward-region activation correlated with the amount of drug use reported.
During the feedback phase of the task, both groups showed nucleus accumbens activation, but cannabis users additionally showed dorsal caudate activation that controls did not.
Why it matters
Social influence is one of the strongest predictors of drug use initiation and maintenance, yet the brain mechanisms underlying social influence in drug users are poorly understood. This study suggests that cannabis users may find following peer influence more rewarding, which could reinforce continued use in social contexts.
The numbers in context
Twenty cannabis users vs. 20 controls, ages 18-25. Nucleus accumbens activation during group-congruent choices correlated with amount of drug use. Cannabis users but not controls showed caudate activation when processing social information and during feedback.
How the study worked
Cross-sectional fMRI study comparing 20 marijuana-using young adults (ages 18-25) with 20 age-matched controls. Participants completed a decision-making task where they could follow or go against group influence while undergoing functional MRI. A priori analyses focused on the nucleus accumbens, with additional analyses across the striatum.
What this study cannot tell us
Cross-sectional design cannot determine whether brain differences preceded cannabis use or resulted from it. Small sample size limits statistical power. Unknown whether peers in the task were perceived as relevant by participants. Cannabis use was self-reported.
How to read the evidence
Well-designed fMRI study with appropriate controls and a priori analyses, but small sample size and cross-sectional design limit conclusions.
When this study was published
Published in 2016. Neuroimaging methods and our understanding of social neuroscience have continued to advance.
The bigger picture
This research connects two well-established findings: the role of social influence in drug use and the involvement of the brain's reward system in addiction. The fact that following social influence activated reward regions specifically in cannabis users suggests a neural mechanism by which peer pressure may maintain cannabis use.
Questions still open
- Do these brain activation differences exist before cannabis use begins, making some people more susceptible to social influence? Would these patterns change if participants stopped using cannabis? Does the intensity of social influence activation predict future drug use?
Common questions
Does cannabis make you more susceptible to peer pressure?
Why does this matter for young people?
Read the original research
Variable activation in striatal subregions across components of a social influence task in young adult cannabis users.
Brain and behavior, 6(5), e00459
Citation
Gilman, Jodi M; Lee, Sang; Kuster, John K; Lee, Myung Joo; Kim, Byoung Woo; van der Kouwe, Andre; Blood, Anne J; Breiter, Hans C. (2016). Variable activation in striatal subregions across components of a social influence task in young adult cannabis users.. Brain and behavior, 6(5), e00459. https://doi.org/10.1002/brb3.459
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