Grey matter morphometry in young adult e-cigarette users, tobacco cigarette users & non-using controls.

Despite the rise in electronic cigarette use in recent years, the neurobiological effects of daily e-cigarette use versus smoking cigarettes in young adults remains unknown. This study aimed to investigate the impact of regular, exclusive e-cigarette use on grey matter morphometry in young adults, age 18-25. Structural MRI data were collected from 3 distinct groups of participants (n = 78): daily, exclusive e-cigarette users; tobacco cigarette users; and non-using controls, to assess grey matter volume (GMV) differences. Voxel-based morphometry revealed significant GMV reductions in tobacco cigarette users in the left fusiform gyrus (FG), left and right inferior temporal gyrus (IFG), right middle temporal gyri, and right middle cingulate gyrus (MCG), compared to controls, as well as the anterior cingulate cortex (ACC), compared to both e-cigarette users and controls, even after adjusting for nicotine exposure history. Partial correlation analyses revealed that in tobacco cigarette users, GMV in the FG, ITG, MTG, and MCG displayed a strong, negative association with exposure history but not with nicotine dependence. GMV of the ACC was not associated with duration of use or nicotine dependence score, suggesting distinct relationships between ACC volume and smoking status and FG/ITG/MTG/MCG volume and smoking status. This indicates a distinct difference between regular tobacco cigarette and e-cigarette use, perhaps a relatively safer profile of e-cigarette use on GMV. These findings suggest that factors beyond nicotine, such as other toxicants in tobacco cigarette smoke, may contribute to the observed brain atrophy, or imply potential pre-existing vulnerabilities that might predispose individuals to take up smoking.