These findings are largely consistent with our previous structural imaging studies that found small yet significant effects of marijuana use on adolescent brain structure and function 34, 37, and stronger associations between alcohol use and tissue status. In a study that looked specifically at adolescents with alcohol use disorders, we found reduced white matter microstructural integrity compared to demographically matched youths without alcohol use disorders 47. Significantly lower FA was found in the splenium of the corpus callosum, and trends for lower FA were also found in the rest of the corpus callosum, suggesting possible alcohol-related white matter alterations. The callosal fibers are a massive collection of white matter tissue that connect the left and right hemispheres of the brain, and are important for efficient transfer of information. Microstructural changes in the corpus callosum may underlie neurocognitive changes associated with alcohol use during adolescent brain maturation. Notably, decreased white-matter integrity was significantly related to longer duration of heavy alcohol use, greater number of past alcohol withdrawal symptoms, and recent consumption of large amounts of alcohol.
