Investigating the assocation between smoking, environmental tobacco smoke exposure and reward-related brain activity in adolescent experimental smokers

Description: Reduced anticipatory reward-related activity, especially in the ventral striatum (VS), underlies adolescent vulnerability to develop nicotine dependence. However, it remains unclear whether nicotine uptake caused by environmental tobacco smoke (ETS) exposure might prompt similar changes in the brain’s reward system, rendering adolescents vulnerable for development of nicotine dependence. To gain more insight into the initial phase of smoking and its vulnerability factors, we tested whether ETS exposure and monthly smoking are associated with VS hypoactivity for non-drug rewards in experimental smoking adolescents. Hundred adolescents performed a monetary incentive delay task while brain activity was measured using fMRI. To test the relationship, we used a variety of approaches: 1) a whole-brain voxel-wise approach, 2) an ROI approach with the VS as ROI using frequentist as well as Bayesian statistics, and 3) a small volume voxel-wise approach across the complete striatum. The results converged in revealing no significant relationship between monthly smoking, ETS exposure and reward-related brain activation across the brain or in the (ventral) striatum specifically. However, Bayesian statistics showed only anecdotal evidence for the null hypothesis in the VS. Therefore we cannot distinguish between whether there are or aren’t associations between monthly smoking, ETS exposure and VS activity. Although only anecdotal, the results of this study tend to suggest that VS hypoactivity occurs only after relatively high levels of exposure or is associated with more long term effects of smoking. Future studies need larger sample sizes to reliably distinguish between the null- and alternative model as well as more participants at the high end of ETS exposure and silicone wristbands to better establish (environmental) smoking.