title: Diffusion abnormalities in adolescents and young adults with a history of heavy cannabis use.
abstract: BACKGROUND
  There is growing evidence that adolescence is a key period for neuronal maturation. Despite the high prevalence of marijuana use among adolescents and young adults in the United States and internationally, very little is known about its impact on the developing brain. Based on neuroimaging literature on normal brain developmental during adolescence, we hypothesized that individuals with heavy cannabis use (HCU) would have brain structure abnormalities in similar brain regions that undergo development during late adolescence, particularly the fronto-temporal connection.
  
  
  METHODS
  Fourteen young adult males in residential treatment for cannabis dependence and 14 age-matched healthy male control subjects were recruited. Patients had a history of HCU throughout adolescence; 5 had concurrent alcohol abuse. Subjects underwent structural and diffusion tensor magnetic resonance imaging. White matter integrity was compared between subject groups using voxelwise and fiber tractography analysis.
  
  
  RESULTS
  Voxelwise and tractography analyses revealed that adolescents with HCU had reduced fractional anisotropy, increased radial diffusivity, and increased trace in the homologous areas known to be involved in ongoing development during late adolescence, particularly in the fronto-temporal connection via arcuate fasciculus.
  
  
  CONCLUSIONS
  Our results support the hypothesis that heavy cannabis use during adolescence may affect the trajectory of normal brain maturation. Due to concurrent alcohol consumption in five HCU subjects, conclusions from this study should be considered preliminary, as the DTI findings reported here may be reflective of the combination of alcohol and marijuana use. Further research in larger samples, longitudinal in nature, and controlling for alcohol consumption is needed to better understand the pathophysiology of the effect of cannabis on the developing brain.
authors.affiliation: The Children's Hospital of Philadelphia, Philadelphia, PA, United States. ashtari@email.chop.edu
authors.forename: Manzar
authors.initials: M
authors.lastname: Ashtari
authors.forename: Kelly
authors.initials: K
authors.lastname: Cervellione
authors.forename: John
authors.initials: J
authors.lastname: Cottone
authors.forename: Babak A
authors.initials: BA
authors.lastname: Ardekani
authors.forename: Serge
authors.initials: S
authors.lastname: Sevy
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Kumra
mesh_terms: D000293:Adolescent; D000437:Alcoholism / Q000503:physiopathology; D000704:Analysis of Variance; D016880:Anisotropy; D001921:Brain / Q000473:pathology*; D016022:Case-Control Studies; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005625:Frontal Lobe / Q000473:pathology; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D002189:Marijuana Abuse / Q000503:physiopathology*; D009415:Nerve Net / Q000473:pathology; D013702:Temporal Lobe / Q000473:pathology; D055815:Young Adult