White matter tract integrity in cannabis users at different neurodevelopmental stages

[Speaker] Solowij, Nadia:1,2
[Co-author] Jakabek, David:1, Lorenzetti, Valentina:3, Yücel, Murat:3
1:University of Wollongong (Australia), 2:Illawarra Health and Medical Research Institute (Australia), 3:Monash University (Australia)

Conflicting evidence exists on the effects of cannabis use on brain white matter integrity. The literature has focused on younger users. We recruited a sample with a broad range of ages to examine white matter integrity associated with cannabis use measures and neurodevelopmental stage.
Cannabis users (n=56) and nonusers (n=20), 18 to 55 years of age, underwent structural and diffusion MRI scans. Eighteen major white matter tracts were reconstructed using probabilistic tractography. Tract integrity was assessed using fractional anisotropy, axial diffusivity and radial diffusivity.
Cannabis users overall had lower fractional anisotropy in the forceps minor. Younger users showed poorer axonal diffusivity, whereas older users had poorer radial diffusivity, in widespread tracts. Lower axial diffusivity in the cingulum angular bundle was strongly associated with duration of cannabis use.
Cannabis alters brain maturation with differing effects at different neurodevelopmental stages, which may account for the disparate results described in the literature.
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