Abstract: “Rates of cannabis use among adolescents are high, and are increasing concurrent with changes in the legal status of marijuana and societal attitudes regarding its use.

“Recreational cannabis use is understudied, especially in the adolescent period when neural maturation may make users particularly vulnerable to the effects of Δ-9-tetrahydrocannabinol (THC) on brain structure.

“In the current study, we used voxel-based morphometry to compare grey matter volume (GMV) in 46 14-year-old human adolescents (males and females) with just one or two instances of cannabis use and carefully matched THC-naïve controls.

“We identified extensive regions in the bilateral medial temporal lobes as well as the bilateral posterior cingulate, lingual gyri, and cerebellum that showed greater GMV in the cannabis users.

“Analysis of longitudinal data confirmed that GMV differences were unlikely to precede cannabis use. GMV in the temporal regions was associated with poor performance on the Perceptual Reasoning Index and with future generalized anxiety symptoms in the cannabis users.

“Significance: Almost 35% of American 10th graders have reported using cannabis and existing research suggests that initiation of cannabis use in adolescence is associated with long-term neurocognitive defects.

We understand very little about the earliest effects of cannabis use, however, as most research is conducted in adults with a heavy pattern of lifetime use.

This study presents evidence suggesting structural brain abnormalities and diminished cognition following cannabis use in adolescence.

“Converging evidence suggests a role for the endocannabinoid system in these effects. This research is particularly timely as the legal status of cannabis is changing in many jurisdictions and the perceived risk by youth associated with smoking cannabis has declined in recent years, (which is a deception found by this reporter from other research mbmsrmd).

[Grey Matter Volume Differences Associated with Extremely Low Levels of Cannabis Use in Adolescence by Catherine Orr, et al, Journal of Neuroscience 14 January 2019, 3375 17; DOI: 10.1523/J NEUROSCI.3375-17.2018]

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