Deficient Functioning of Frontostriatal Circuits During the Resolution of Cognitive Conflict in Cannabis-Using Youth

A Meta-Analysis of fMRI Studies of Youth Cannabis Use: Alterations in Executive Control, Social Cognition/Emotion Processing, and Reward Processing in Cannabis Using Youth

Background: Adolescent cannabis use (CU) is associated with adverse health outcomes and may be increasing in response to changing cannabis laws. Recent imaging studies have identified differences in brain activity between adult CU and controls that are more prominent in early onset users. Whether these differences are present in adolescent CU and relate to age/developmental stage, sex, or cannabis exposure is unknown. Methods: A systematic review and subsequent effect-size seed-based d mapping (SDM) meta-analysis were conducted to examine differences in blood-oxygen-level-dependent (BOLD) response during fMRI studies between CU and non-using typically developing (TD) youth. Supplemental analyses investigated differences in BOLD signal in CU and TD youth as a function of sex, psychiatric comorbidity, and the dose and severity of cannabis exposure. Results: From 1371 citations, 45 fMRI studies were identified for inclusion in the SDM meta-analysis. These studies compared BOLD response contrasts in 1216 CU and 1486 non-using TD participants. In primary meta-analyses stratified by cognitive paradigms, CU (compared to TD) youth showed greater activation in the rostral medial prefrontal cortex (rmPFC) and decreased activation in the dorsal mPFC (dmPFC) and dorsal anterior cingulate cortex (dACC) during executive control and social cognition/emotion processing, respectively. In meta-regression analyses and subgroup meta-analyses, sex, cannabis use disorder (CUD) severity, and psychiatric comorbidity were correlated with brain activation differences between CU and TD youth in mPFC and insular cortical regions. Activation differences in the caudate, thalamus, insula, dmPFC/dACC, and precentral and postcentral gyri varied as a function of the length of abstinence. Conclusions: Using an SDM meta-analytic approach, this report identified differences in neuronal response between CU and TD youth during executive control, emotion processing, and reward processing in cortical and subcortical brain regions that varied as a function of sex, CUD severity, psychiatric comorbidity, and length of abstinence. Whether aberrant brain function in CU youth is attributable to common predispositional factors, cannabis-induced neuroadaptive changes, or both warrants further investigation.

Potential brain recovery of frontostriatal circuits in heroin users after prolonged abstinence: A preliminary study

Neuroscientists have devoted efforts to explore potential brain recovery after prolonged abstinence in heroin users (HU). However, not much is known about whether frontostriatal circuits can recover after prolonged abstinence in HU. An eight-month longitudinal study was carried out for HU. Two MRI scans were obtained at baseline (HU1) and 8-month follow-up (HU2). The functional and structural connectivities of dorsal and ventral frontostriatal pathways were measured by resting-state functional connectivity (RSFC) and diffusion tensor imaging (DTI). Correlation analyses were employed to reveal the associations between neuroimaging and behavioral changes. Results suggested that relative to healthy controls (HCs), HU1 showed lower fractional anisotropy (FA) in the right dorsolateral prefrontal cortex (DLPFC)-to-caudate tracts and medial orbitofrontal cortex (mOFC)-to-nucleus accumbens (NAc) tracts as well as decreased RSFC in the left mOFC-NAc circuits. Longitudinal results revealed reduced craving and enhanced cognitive control in HU2 compared with HU1. After prolonged abstinence, HU2 showed increased FA values in the right DLPFC-caudate and mOFC-NAc tracts as well as increased RSFC strength in the bilateral mOFC-NAc circuits compared with HU1. In addition, changes in RSFC and FA values in the right mOFC-NAc circuit were negatively correlated with craving score changes. Similarly, negative correlations were also found between changes of RSFC in the bilateral DLPFC-caudate circuits and TMT-A scores. We provided scientific evidence for brain recovery of the dorsal and ventral frontostriatal circuits in HU after prolonged abstinence, and these circuits may be potential neuroimaging biomarkers for cognition and craving changes.

Cannabis and the Developing Adolescent Brain

Purpose of Review

This review summarizes (1) recent trends in delta-9-tetrahydrocannabionol [THC] and cannabidiol (CBD) content in cannabis products, (2) neurobiological correlates of cannabis use on the developing adolescent brain, (3) effects of cannabis on psychiatric symptoms and daily functioning in youth (i.e., academic performance, cognition, sleep and driving), (4) cannabis products used to relieve or treat medical issues in youth, and (5) available treatments for cannabis use disorder in adolescence.

Recent findings

Despite marked increases in THC content and availability of cannabis, there has been a decline in perceived risk and an increase in use of THC extract products among youth in the United States. The primary psychiatric symptoms associated with cannabis use in youth are increased risk for addiction, depressive, and psychotic symptoms. Cannabis alters endocannabinoid system function which plays a central role in modulating the neurodevelopment of reward and stress systems. To date, few studies have examined neurobiological mechanisms underlying the psychiatric sequalae of cannabis exposure in youth. Adolescent cannabis exposure results in impaired cognition, sleep, and driving ability. There are very limited FDA-approved cannabinoid medications, none of them supporting their use for the treatment of psychiatric symptoms. Behavioral therapies are currently the mainstay of treating cannabis misuse, with no pharmacotherapies currently approved by the FDA for cannabis use disorder in youth.

Summary

Here, we summarize the most up-to-date knowledge on the neurobiological psychiatric, and daily function effects of the most commonly used cannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). We then review FDA approved medical use of cannabinoid treatments as well as pharmacological and psychological treatments for cannabis use disorder in youth. Our current understanding of the effects of cannabis on the developing brain and treatments for cannabis misuse in youth remain limited. Future research aimed at examining the neurobiological effects of cannabis, with objective measures of exposure, over the course of pediatric development and in relation to psychiatric symptoms are needed.

Reward, Control & Decision-Making in Cannabis Use Disorder: Insights from Functional MRI

The recreational consumption of cannabis has increased significantly across the world with an estimated 180 million people currently using. In the United States, 4.1 million are currently diagnosed with cannabis use disorder. Cannabis dependence and abuse was combined into a single entity as a behavioral disorder with a problematic pattern of cannabis use and termed cannabis use disorder by the Diagnostic and Statistical Manual of Mental Disorders. Chronic use of cannabis has been linked with region-specific effects across the brain mediating reward processing, cognitive control and decision-making that are central to understanding addictive behaviors. This review presents a snapshot of the current literature assessing the effects of chronic cannabis use on human brain function via functional MRI. Studies employing various paradigms and contrasting cognitive activation amongst cannabis users and non-users were incorporated. The effects of trans-del-ta-9-tetrahydrocannabinol (Δ9-THC) in marijuana and other preparations of cannabis are mediated by the endocannabinoid system, which is also briefly introduced.Much variation exists in the current literature regarding the functional changes associated with chronic cannabis use. One possible explanation for this variation is the heterogeneity in study designs, with little implementation of standardized diagnostic criteria when selecting chronic users, distinct time points of participant assessment, differing cognitive paradigms and imaging protocols. As such, there is an urgent requirement for future investigations that further characterize functional changes associated with chronic cannabis use.

Editorial: Causal, Predispositional, or Correlate? Group Differences in Cognitive Control-Related Brain Function in Cannabis-Using Youth Raise New Questions

Increasingly permissive attitudes and laws surrounding cannabis have been accompanied by more prevalent use and increased perceptions of its safety.¹ However, in stark contrast to this sea-change, remarkably little is known about the potential consequences and etiology of cannabis involvement. In particular, it is unclear what biological mechanisms may undergird associations with negative outcomes (eg, reduced cognition, increased psychosis, depression)² and whether these substrates arise from cannabis use and/or represent predispositional risk factors. As cannabis remains at the forefront of public discussion and policy, it is increasingly important to identify potential biological mechanisms contributing to associations with negative outcomes and evaluate the plausibility that these represent a consequence of exposure and/or predispositional risk factors or nonetiologic correlates. The knowledge generated from this Herculean task may dam the present sea-change of increasing cannabis permissiveness and/or remove the few remaining boulders impeding it.