In the current study, we examined the integrity of neuroanatomical pathways in adolescent marijuana users with concomitant alcohol use through DTI analysis. Based on findings of altered neural networks in marijuana-using teens, neurobiological evidence of cannabis receptors within myelin precursors, and persistent impairing effects of alcohol on myelination, we predicted that chronic MJ+ALC users would show poorer white matter integrity than non-users. Considering activation differences in fMRI studies in alcohol and marijuana users (Jacobsen et al., 2007; Rangaswamy et al., 2004; Schweinsburg et al., 2008b; Tapert et al., 2004; Tapert et al., 2007), we hypothesized white matter fiber integrity to be altered in fronto-parietal circuits.
