title: Recreational marijuana use impacts white matter integrity and subcortical (but not cortical) morphometry.
abstract: A recent shift in legal and social attitudes toward marijuana use has also spawned a surge of interest in understanding the effects of marijuana use on the brain. There is considerable evidence that an adolescent onset of marijuana use negatively impacts white matter coherence. On the other hand, a recent well-controlled study demonstrated no effects of marijuana use on the morphometry of subcortical or cortical structures when users and non-users were matched for alcohol use. Regardless, most studies have involved small, carefully selected samples, so the ability to generalize to larger populations is limited. In an attempt to address this issue, we examined the effects of marijuana use on white matter integrity and cortical and subcortical morphometry using data from the Human Connectome Project (HCP) consortium. The HCP data consists of ultra-high resolution neuroimaging data from a large community sample, including 466 adults reporting recreational marijuana use. Rather than just contrasting two groups of individuals who vary significantly in marijuana usage as typifies prior studies, we leveraged the large sample size provided by the HCP data to examine parametric effects of recreational marijuana use. Our results indicate that the earlier the age of onset of marijuana use, the lower was white matter coherence. Age of onset also also affected the shape of the accumbens, while the number of lifetime uses impacted the shape of the amygdala and hippocampus. Marijuana use had no effect on cortical volumes. These findings suggest subtle but significant effects of recreational marijuana use on brain structure.
authors.affiliation: Department of Psychology, Texas A&M University, United States; Institute of Cognitive Science, University of Colorado Boulder, United States.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Orr
authors.affiliation: Department of Psychology and Neuroscience, University of Colorado Boulder, United States.
authors.forename: Courtnie J
authors.initials: CJ
authors.lastname: Paschall
authors.affiliation: Institute of Cognitive Science, University of Colorado Boulder, United States; Department of Psychology and Neuroscience, University of Colorado Boulder, United States.
authors.forename: Marie T
authors.initials: MT
authors.lastname: Banich
mesh_terms: D000328:Adult; D000679:Amygdala / Q000187:drug effects / Q000473:pathology; D001921:Brain / Q000187:drug effects* / Q000473:pathology*; D002188:Cannabis / Q000009:adverse effects*; D002540:Cerebral Cortex / Q000187:drug effects / Q000473:pathology; D056324:Diffusion Tensor Imaging; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008385:Marijuana Smoking / Q000009:adverse effects*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000473:pathology; D066127:White Matter / Q000187:drug effects* / Q000473:pathology*; D055815:Young Adult
keywords: Connectivity; DTI; Human Connectome Project; MRI; Marijuana; Morphometry