Chronic THC intake modifies fundamental cerebellar functions

Effects of prenatal synthetic cannabinoid exposure on the cerebellum of adolescent rat offspring

Cannabis is the most commonly used illicit drug worldwide. Recently, cannabis use among young pregnant women has greatly increased. However, prenatal cannabinoid exposure leads to long-lasting cognitive, motor, and behavioral deficits in the offspring and alterations in neural circuitry through various mechanisms. Although these effects have been studied in the hippocampus, the effects of prenatal cannabinoid exposure on the cerebellum are not well elucidated. The cerebellum plays an important role in balance and motor control, as well as cognitive functions such as attention, language, and procedural memories. The aim of this study was to investigate the effects of prenatal cannabinoid exposure on the cerebellum of adolescent offspring. Pregnant rats were treated with synthetic cannabinoid agonist WIN55,212-2, and the offspring were evaluated for various cerebellar markers of oxidative stress, mitochondrial function, and apoptosis. Additionally, signaling proteins associated with glutamate dependent synaptic plasticity were examined. Administration of WIN55,212-2 during pregnancy altered markers of oxidative stress by significantly reducing oxidative stress and nitrite content. Mitochondrial Complex I and Complex IV activities were also enhanced following prenatal cannabinoid exposure. With regard to apoptosis, pP38 levels were significantly increased, and proapoptotic factor caspase-3 activity, pERK, and pJNK levels were significantly decreased. CB1R and GluA1 levels remained unchanged; however, GluN2A was significantly reduced. There was a significant decrease in MAO activity although tyrosine hydroxylase activity was unaltered. Our study indicates that the effects of prenatal cannabinoid exposure on the cerebellum are unique compared to other brain regions by enhancing mitochondrial function and promoting neuronal survival. Further studies are required to evaluate the mechanisms by which prenatal cannabinoid exposure alters cerebellar processes and the impact of these alterations on behavior.

Association of Naturalistic Administration of Cannabis Flower and Concentrates With Intoxication and Impairment

IMPORTANCE

The rapidly growing legal cannabis market includes new and highly potent products, the effects of which, to our knowledge, have not previously been examined in biobehavioral research studies because of federal restrictions on cannabis research.

OBJECTIVE

To use federally compatible, observational methods to study high-∆9-tetrahydrocannabinol (THC) legal market forms of cannabis.

DESIGN, SETTING, AND PARTICIPANTS

In this cohort study with a between-groups design that was conducted in a community and university setting, cannabis flower users and concentrate users were randomly assigned to higher- vs lower-THC products within user groups. Participants completed a baseline and an experimental mobile laboratory assessment that included 3 points: before, immediately after, and 1 hour after ad libitum legal market flower and concentrate use. Of the 133 individuals enrolled and assessed, 55 regular flower cannabis users (41.4%) and 66 regular concentrate cannabis users (49.6%) complied with the study's cannabis use instructions and had complete data across primary outcomes.

EXPOSURES

Flower users were randomly assigned to use either 16% or 24% THC flower and concentrate users were randomly assigned to use either 70% or 90% THC concentrate that they purchased from a dispensary.

MAIN OUTCOMES AND MEASURES

Primary outcome measures included plasma cannabinoids, subjective drug intoxication, and neurobehavioral tasks testing attention, memory, inhibitory control, and balance.

RESULTS

A total of 121 participants completed the study for analysis: 55 flower users (mean [SD] age, 28.8 [8.1] years; 25 women [46%]) and 66 concentrate users (mean [SD] age, 28.3 [10.4] years; 30 women [45%]). Concentrate users compared with flower users exhibited higher plasma THC levels and 11-hydroxyΔ9-THC (THC's active metabolite) across all points. After ad libitum cannabis administration, mean plasma THC levels were 0.32 (SE = 0.43) μg/mL in concentrate users (to convert to millimoles per liter, multiply by 3.18) and 0.14 (SE = 0.16) μg/mL in flower users. Most neurobehavioral measures were not altered by short-term cannabis consumption. However, delayed verbal memory (F1,203 = 32.31; P < .001) and balance function (F1,203 = 18.88; P < .001) were impaired after use. Differing outcomes for the type of product (flower vs concentrate) or potency within products were not observed.

CONCLUSIONS AND RELEVANCE

This study provides information about the association of pharmacological and neurobehavioral outcomes with legal market cannabis. Short-term use of concentrates was associated with higher levels of THC exposure. Across forms of cannabis and potencies, users' domains of verbal memory and proprioception-focused postural stability were primarily associated with THC administration.

Genome-wide association study implicates CHRNA2 in cannabis use disorder

Cannabis is the most frequently used illicit psychoactive substance worldwide; around one in ten users become dependent. The risk for cannabis use disorder (CUD) has a strong genetic component, with twin heritability estimates ranging from 51 to 70%. Here we performed a genome-wide association study of CUD in 2,387 cases and 48,985 controls, followed by replication in 5,501 cases and 301,041 controls. We report a genome-wide significant risk locus for CUD (P = 9.31 × 10^-12) that replicates in an independent population (P_replication = 3.27 × 10^-3, P_{meta-analysis} = 9.09 × 10^-12). The index variant (rs56372821) is a strong expression quantitative trait locus for cholinergic receptor nicotinic α2 subunit (CHRNA2); analyses of the genetically regulated gene expression identified a significant association of CHRNA2 expression with CUD in brain tissue. At the polygenic level, analyses revealed a significant decrease in the risk of CUD with increased load of variants associated with cognitive performance. The results provide biological insights and inform on the genetic architecture of CUD.

Cortical thickness in adolescent marijuana and alcohol users: A three-year prospective study from adolescence to young adulthood

Studies suggest marijuana impacts gray and white matter neural tissue development, however few prospective studies have determined the relationship between cortical thickness and cannabis use spanning adolescence to young adulthood. This study aimed to understand how heavy marijuana use influences cortical thickness trajectories across adolescence. Subjects were adolescents with heavy marijuana use and concomitant alcohol use (MJ+ALC, n=30) and controls (CON, n=38) with limited substance use histories. Participants underwent magnetic resonance imaging and comprehensive substance use assessment at three independent time points. Repeated measures analysis of covariance was used to look at main effects of group, time, and Group × Time interactions on cortical thickness. MJ+ALC showed thicker cortical estimates across the brain (23 regions), particularly in frontal and parietal lobes (ps<.05). More cumulative marijuana use was associated with increased thickness estimates by 3-year follow-up (ps<.05). Heavy marijuana use during adolescence and into young adulthood may be associated with altered neural tissue development and interference with neuromaturation that can have neurobehavioral consequences. Continued follow-up of adolescent marijuana users will help understand ongoing neural changes that are associated with development of problematic use into adulthood, as well as potential for neural recovery with cessation of use.

Cortical thickness and neurocognition in adolescent marijuana and alcohol users following 28 days of monitored abstinence

OBJECTIVE

Adolescent marijuana use continues to increase in prevalence as harm perception declines. Better understanding of marijuana's impact on neurodevelopment is crucial. This prospective study aimed to investigate cortical thickness and neurocognitive performance before and after 28 days of monitored abstinence in adolescent marijuana and alcohol users.

METHOD

Subjects (N = 54; >70% male) were adolescent marijuana users (ages 15-18 years) with regular alcohol use (MJ + ALC; n = 24) and non-using controls (CON; n = 30) who were compared before and after 4 weeks of sequential urine toxicology to confirm abstinence. Participants underwent magnetic resonance imaging, neuropsychological assessment, and substance use assessment at both time points. Repeated-measures analysis of covariance was used to look at the main effects of group, time, and Group × Time interactions on cortical thickness and neurocognitive functioning. Bivariate correlations estimated associations between cortical thickness, substance use severity, and cognitive performance.

RESULTS

Marijuana users showed thicker cortices than controls in the left entorhinal cortex (ps < .03) before and after monitored abstinence, after adjusting for lifetime alcohol use. More lifetime marijuana use was linked to thinner cortices in temporal and frontal regions, whereas more lifetime alcohol use and heavy episodic drinking episodes was linked to thicker cortices in all four lobes (ps < .05). Age of onset of regular marijuana use was positively related to cortical thickness (ps < .03).

CONCLUSIONS

Adolescent alcohol and marijuana use may be linked to altered longer-term neurodevelopmental trajectories and compromised neural health. Cortical thickness alterations and dose-dependent associations with thickness estimates were observed both before and after monitored abstinence and suggest neural differences continue to persist 28 days after cessation of marijuana use. Neural recovery may be identified with longer follow-up periods; however, observed changes related to use severity could have implications for future psychosocial outcomes.

Neuropsychological performance in adolescent marijuana users with co-occurring alcohol use: A three-year longitudinal study

OBJECTIVE

The effect of adolescent marijuana use on brain development remains unclear despite relaxing legal restrictions, decreased perceived harm, and increasing use rates among youth. The aim of this 3-year prospective study was to evaluate the long-term neurocognitive effects of adolescent marijuana use.

METHOD

Adolescent marijuana users with concomitant alcohol use (MJ + ALC, n = 49) and control teens with limited substance use histories (CON, n = 59) were given neuropsychological and substance use assessments at project baseline, when they were ages 16-19. They were then reassessed 18 and 36 months later. Changes in neuropsychological measures were evaluated with repeated measures analysis of covariance (ANCOVA), controlling for lifetime alcohol use, and examined the effects of group, time, and group by time interactions on cognitive functioning.

RESULTS

MJ + ALC users performed significantly worse than controls, across time points, in the domains of complex attention, memory, processing speed, and visuospatial functioning (ps <.05). Earlier age of marijuana use onset was associated with poorer processing speed and executive functioning by the 3-year follow-up (ps ≤.02).

CONCLUSIONS

Frequent marijuana use throughout adolescence and into young adulthood appeared linked to worsened cognitive performance. Earlier age of onset appears to be associated with poorer neurocognitive outcomes that emerge by young adulthood, providing further support for the notion that the brain may be uniquely sensitive to frequent marijuana exposure during the adolescent phase of neurodevelopment. Continued follow-up of adolescent marijuana users will determine the extent of neural recovery that may occur if use abates.