Daily Marijuana Use Is Not Associated with Brain Morphometric Measures in Adolescents or Adults

Abstract

Recent research has suggested that marijuana use is associated with volumetric and shape differences in subcortical structures, including the nucleus accumbens and amygdala, in a dose-dependent fashion. Replication of such results in well controlled studies is essential to clarify the effects of marijuana. To that end, this retrospective study examined brain morphology in a sample of adult daily marijuana users (n ϭ 29) versus nonusers (n ϭ 29) and a sample of adolescent daily users (n ϭ 50) versus nonusers (n ϭ 50). Groups were matched on a critical confounding variable, alcohol use, to a far greater degree than in previously published studies. We acquired high-resolution MRI scans, and investigated group differences in gray matter using voxel-based morphometry, surface-based morphometry, and shape analysis in structures suggested to be associated with marijuana use, as follows: the nucleus accumbens, amygdala, hippocampus, and cerebellum. No statistically significant differences were found between daily users and nonusers on volume or shape in the regions of interest. Effect sizes suggest that the failure to find differences was not due to a lack of statistical power, but rather was due to the lack of even a modest effect. In sum, the results indicate that, when carefully controlling for alcohol use, gender, age, and other variables, there is no association between marijuana use and standard volumetric or shape measurements of subcortical structures.

Prenatal exposure to cannabinoids evokes long-lasting functional alterations by targeting CB 1 receptors on developing cortical neurons

“…The susceptibility of axonal connectivity to embryonic CB 1 R loss of function (present report) may persist at later developmental stages in critically susceptible areas, as it has been demonstrated that THC consumption in adolescents can also result in axonal connectivity deficits (29). Nevertheless, in another study, daily marijuana consumption did not induce volumetric changes in several brain areas (30).…”

Can we make cannabis safer?

“…Two other MRI studies have reported that cannabis users had smaller hippocampal volumes than non-users, but that this was not evident in cannabis users with hair samples that were positive for CBD 40,41 . However, the extent to which cannabis use is associated with neuroanatomical changes remains controversial: studies that have matched participants on alcohol use, or have accounted for heritable and genetic risk, have failed to find an association between cannabis use and brain structure [42][43][44] .…”

Quantifying absolute glutamate concentrations in nucleus accumbens of prescription opioid addicts by using 1H MRS

“…And we did not separate gray matter from VOI. Previous studies have reported that there are no change in volume of the NAc structure in patients with prescription opioid dependence (Upadhyay et al, 2010) or marijuana use (Weiland, Thayer, & Depue, 2015). But, Seifert et al (2015) reported that there might be structural differences in the NAc of heroin-dependent patients in comparison with healthy controls.…”