and/or increased mean diffusivity throughout the brain. McQueeney et al. (31) reported that binge-drinking adolescents, as compared to controls, had significantly lower FA values in 18 brain regions, including multiple areas of the corpus callosum, the superior longitudinal fasciculus, the corona radiate, portions of the internal and external capsules, and cerebellum. Age and sex were apparently not controlled in these analyses. Bava et al. (32) reported upon a larger group (that may have overlapped with the McQueeney sample), finding that combined alcohol and marijuana users had lower FA in 10 fiber tracts. Within the same lab, Jacobus et al. (29) reported that adolescent binge drinkers without concomitant marijuana use had significantly lower FA values in eight brain regions, including the superior longitudinal fasciculus. Given that these studies were cross-sectional, cause-effect associations cannot be determined. A more recent study by Bava et al. (77) followed heavy alcohol plus marijuana using adolescents versus those with less significant use over an 18-month period. At follow-up, the substance use group exhibited lower FA values in seven fiber tracts, including the superior longitudinal fasciculus, thalamic fibers and the corona radiata. Notably, higher mean diffusivity in the superior longitudinal fasciculus was associated with more alcohol use
