Background and aimsCognitive impairment has been associated with excessive alcohol use, but its neural basis is poorly understood. Chronic excessive alcohol use in adolescence may lead to neuronal loss and volumetric changes in the brain. Our objective was to compare the grey matter volumes of heavy- and light-drinking adolescents. DesignThis was a longitudinal study: heavy-drinking adolescents without an alcohol use disorder and their light-drinking controls were followed-up for 10 years using questionnaires at three time-points. Magnetic resonance imaging was conducted at the last time-point. SettingThe area near Kuopio University Hospital, Finland. ParticipantsThe 62 participants were aged 22-28years and included 35 alcohol users and 27 controls who had been followed-up for approximately 10 years. MeasurementsAlcohol use was measured by the Alcohol Use Disorders Identification Test (AUDIT)-C at three time-points during 10years. Participants were selected based on their AUDIT-C score. Magnetic resonance imaging was conducted at the last time-point. Grey matter volume was determined and compared between heavy- and light-drinking groups using voxel-based morphometry on three-dimensional T1-weighted magnetic resonance images using predefined regions of interest and a threshold of P<0.05, with small volume correction applied on cluster level. FindingsGrey matter volumes were significantly smaller among heavy-drinking participants in the bilateral anterior cingulate cortex, right orbitofrontal and frontopolar cortex, right superior temporal gyrus and right insular cortex compared to the control group (P<0.05, family-wise error-corrected cluster level). ConclusionsExcessive alcohol use during adolescence appears to be associated with an abnormal development of the brain grey matter. Moreover, the structural changes detected in the insula of alcohol users may reflect a reduced sensitivity to alcohol's negative subjective effects.