Grey Matter Volume Differences Associated with Extremely Low Levels of Cannabis Use in Adolescence

Cannabis use and psychotic-like experiences: A systematic review of biological vulnerability, potency effects, and clinical trajectories

Epidemiological data have provided evidence that psychotic-like experiences (PLEs) occur in the general population without clinical impairment. According to the psychosis continuum hypothesis, PLEs are subject to multiple risk factors. This review synthesizes current research on biological, substance use-related, and environmental risk factors for PLEs in non-clinical populations. PubMed/Medline and Scopus databases were searched for peer-reviewed studies published until January 2024 investigating risk factors for PLEs in non-clinical samples. Following PRISMA guidelines, 38 full-text articles were analyzed after title/abstract and full-text screening (PROSPERO registration ID: N 1001,807). Four main risk factor categories emerged. Biological vulnerabilities included specific metabolic profiles, genetic predisposition, and neurobiological alterations. Substance use patterns, particularly high-potency cannabis, showed significant associations with PLEs, with evidence for bidirectional relationships. Socio-demographic factors revealed influences of digital media use, ethnic density, and gender differences. Outcome studies demonstrated associations between PLEs and consequences including suicidal behavior and cognitive impairments. Findings suggest a complex interplay between multiple risk factors in PLE development. More attention should be paid to the interaction between biological vulnerabilities and environmental factors, as these experiences may represent important markers for mental health outcomes. A comprehensive assessment approach and proactive early intervention strategies are essential for the timely identification and management of at-risk individuals. Our findings support a multifactorial model where genetic vulnerabilities, cannabis use patterns, and socio-environmental factors influence PLE trajectories. The bidirectional cannabis-PLE relationship suggests self-regulatory mechanisms that could inform preventive interventions. Early identification of PLEs in young cannabis users represents a crucial opportunity for targeted clinical interventions.

Cannabinoids and the heart-a psychiatrist's perspective

The partial legalization of cannabis in Germany in 2024 will affect both medical and recreational use of cannabis. Tetrahydrocannabinol (THC), the main psychoactive component of the cannabis plant, influences heart rate and blood pressure through the endocannabinoid system. Acute and chronic use can pose cardiovascular risks. There is evidence of a link between cannabis use and cardiovascular events such as stroke and myocardial infarction, although studies show conflicting results. The non-psychoactive cannabidiol (CBD) could have anti-inflammatory and antioxidant effects. Smoking cannabis poses additional cardiovascular risks similar to tobacco. Given these risks, cardiologists should routinely ask their patients about possible cannabis use and inform them about the potential cardiovascular dangers. The article also highlights the psychiatric risks of cannabis use, including dependence and psychosis, and emphasizes the need for interdisciplinary collaboration between cardiologists and psychiatrists to effectively manage cannabis-related health problems.

Cannabinoids Used for Medical Purposes in Children and Adolescents: A Systematic Review and Meta-Analysis

Importance

Cannabinoids are increasingly used for medical purposes in children. Evidence of the safety of cannabinoids in this context is sparse, creating a need for reliable information to close this knowledge gap.

Objective

To study the adverse event profile of cannabinoids used for medical purposes in children and adolescents.

Data Sources

For this systematic review and meta-analysis, MEDLINE, Embase, PsycINFO, and the Cochrane Library were searched for randomized clinical trials published from database inception to March 1, 2024, for subject terms and keywords focused on cannabis and children and adolescents. Search results were restricted to human studies in French or English.

Study Selection

Two reviewers independently performed the title, abstract, and full-text review, data extraction, and quality assessment. Included studies enrolled at least 1 individual 18 years or younger, had a natural or pharmaceutical cannabinoid used as an intervention to manage any medical condition, and had an active comparator or placebo.

Data Extraction and Synthesis

Two reviewers performed data extraction and quality assessment independently. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline and PRISMA-S guideline were used. Data were pooled using a random-effects model.

Main Outcomes and Measures

The primary outcome was the incidence of withdrawals, withdrawals due to adverse events, overall adverse events, and serious adverse events in the cannabinoid and control arms. Secondary outcomes were the incidence of specific serious adverse events and adverse events based on organ system involvement.

Results

Of 39 175 citations, 23 RCTs with 3612 participants were included (635 [17.6%] female and 2071 [57.3%] male; data not available from 2 trials); 11 trials (47.8%) included children and adolescents only, and the other 12 trials (52.2%) included children, adolescents, and adults. Interventions included purified cannabidiol (11 [47.8%]), nabilone (4 [17.4%]), tetrahydrocannabinol (3 [13.0%]), cannabis herbal extract (3 [13.0%]), and dexanabinol (2 [8.7%]). The most common indications were epilepsy (9 [39.1%]) and chemotherapy-induced nausea and vomiting (7 [30.4%]). Compared with the control, cannabinoids were associated with an overall increased risk of adverse events (risk ratio [RR], 1.09; 95% CI, 1.02-1.16; I2 = 54%; 12 trials), withdrawals due to adverse events (RR, 3.07; 95% CI, 1.73-5.43; I2 = 0%; 14 trials), and serious adverse events (RR, 1.81; 95% CI, 1.21-2.71; I2 = 59%; 11 trials). Cannabinoid-associated adverse events with higher RRs were diarrhea (RR, 1.82; 95% CI, 1.30-2.54; I2 = 35%; 10 trials), increased serum levels of aspartate aminotransferase (RR, 5.69; 95% CI, 1.74-18.64; I2 = 0%; 5 trials) and alanine aminotransferase (RR, 5.67; 95% CI, 2.23-14.39; I2 = 0%; 6 trials), and somnolence (RR, 2.28; 95% CI, 1.83-2.85; I2 = 8%; 14 trials).

Conclusions and Relevance

In this systematic review and meta-analysis, cannabinoids used for medical purposes in children and adolescents in RCTs were associated with an increased risk of adverse events. The findings suggest that long-term safety studies, including those exploring cannabinoid-related drug interactions and tools that improve adverse event reporting, are needed.

Hippocampal gray matter volume in young adulthood varies with adolescent alcohol use

Adolescent substance use is linked with negative future outcomes (e.g., depression, anxiety, substance use disorder). Given that the brain undergoes significant maturation during adolescence, this developmental period may represent a time of particular vulnerability to substance use. Neuroimaging research has largely focused on heavy or binge patterns of substance use; thus, relatively less is known about the neural impact of a broader range of adolescent substance use. Characterizing the neural impact of a broader range of adolescent substance use may inform prevention and treatment efforts. The present study investigated relationships between adolescent substance use trajectories (i.e., alcohol, tobacco, and cannabis) and gray matter volume in young adulthood. Substance use was assessed in 1,594 participants at ages 11, 13, 16, and 19. Following the last assessment, 320 participants completed a single magnetic resonance imaging session to assess brain gray matter volume. Latent growth curve models were used to estimate growth parameters characterizing alcohol, tobacco, and cannabis use trajectories for each participant. These growth parameters (i.e., intercept, linear slope, and quadratic slope) were then used as predictors of gray matter volume. The gray matter volume of the hippocampus was positively associated with age 14 alcohol use (i.e., intercept) but not other trajectories (i.e., progression or acceleration) or substances (tobacco or cannabis). These results provide new insight into the neural impact of distinct adolescent alcohol, tobacco, and cannabis use trajectories, which may help to refine prevention and treatment efforts. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Examining associations between brain morphology in late childhood and early alcohol or tobacco use initiation in adolescence: Findings from a large prospective cohort

A prominent challenge in understanding neural consequences of substance use involves disentangling predispositional risk factors from resulting consequences of substance use. Existing literature has identified pre-existing brain variations as vulnerability markers for substance use throughout adolescence. As early initiation of use is an important predictor for later substance use problems, we examined whether pre-existing brain variations are associated with early initiation of use. In the Generation R Study, a prospective population-based cohort, brain morphology (gray matter volume, cortical thickness and surface area) was assessed at ages 10 and 14 using neuroimaging. In the second wave, participants reported on alcohol and tobacco use initiation. From a base study population (N = 3019), we examined the longitudinal (N = 2218) and cross-sectional (N = 1817) association between brain morphology of frontolimbic regions of interest known to be associated with substance use risk, and very early (age < 13) alcohol/tobacco use initiation. Additionally, longitudinal and cross-sectional associations were examined with a brain surface-based approach. Models were adjusted for age at neuroimaging, sex and relevant sociodemographic factors. No associations were found between brain morphology (ages 10 and 14) and early alcohol/tobacco use initiation (<13 years). Sex-specific analyses suggested a cross-sectional association between smaller brain volume and early initiated tobacco use in girls. Our findings are important for interpreting studies examining neural consequences of substance use in the general population. Future longitudinal studies are needed to specify whether these findings can be extended to initiation and continuation of alcohol/tobacco use in later stages of adolescence.

High-Risk Cannabis Use: A Proposal of an Operational Definition through Delphi Methodology for Scientific Consensus

INTRODUCTION

Cannabis ranks as one of the most widely used psychoactive substances worldwide. Its usage has been reported as a risk factor for developing a variety of physical and mental health issues, alongside social and economic problems. According to the World Health Organization (WHO), hazardous (or high-risk) substance use is defined as "a pattern of substance use that increases the risk of harmful consequences for the user." The primary objective of this study was to achieve a consensus on an operational definition of high-risk cannabis use suitable for a European jurisdiction (Spain).

METHODS

A three round Delphi study was conducted. The Delphi technique entails group decision-making and iterative forecasting by consulting a panel of experts and conducting systematic feedback rounds. An online survey was distributed among a diverse expert panel comprising professionals from Spain working on fields related to cannabis use (research, policy planning, and clinical professionals). One-hundred ninety-nine invitations were sent to experts, of which forty-five (22.6%) accepted to participate. All participants were provided the option to revise a background document with the latest compiled scientific evidence and guidelines related to health and social conditions associated to cannabis usage. This background document also proposed the quantification of dose using a standardized unit established for the population of Spain (the Standard Joint Unit or SJU) based on quantity of cannabis main psychoactive constituent, 9-tetrahydrocannabinol (9-THC) (1 SJU = 1 joint = 0.25 g of cannabis = 7 mg of 9-THC). Three rounds of Likert scale and open-ended questions were administered until consensus, defined as ≥75% agreement, was attained.

RESULTS

Consensus was reached on defining high-risk cannabis use as the usage of more than 4 SJU (>28 mg THC) per week or any use of cannabis with potency >10% THC. Concurrent use of cannabis with other drugs was also considered high risk, while the smoked route was considered the riskiest administration route. It was also agreed that vulnerable groups for high-risk cannabis use (for whom any pattern of cannabis use represents high risk of harm) include individuals under the age of 21, pregnant or breastfeeding women, individuals with psychiatric history, those with medical health issues related to cannabis use, professional drivers and heavy machine operators.

CONCLUSION

This operational definition of high-risk cannabis use for Spain elucidates usage patterns and individual vulnerability factors predictive of heightened harm. Its adoption holds potential to inform decision-making among individuals, professionals, and policy-makers, facilitating evidence-based interventions aimed at prevention and risk reduction.

The Development of Cannabinoids as Therapeutic Agents in the United States

Cannabis is one of the oldest and widely used substances in the world. Cannabinoids within the cannabis plant, known as phytocannabinoids, mediate cannabis' effects through interactions with the body's endogenous cannabinoid system. This endogenous system, the endocannabinoid system, has important roles in physical and mental health. These roles point to the potential to develop cannabinoids as therapeutic agents while underscoring the risks related to interfering with the endogenous system during nonmedical use. This scoping narrative review synthesizes the current evidence for both the therapeutic and adverse effects of the major (i.e., Δ9-tetrahydrocannabinol and cannabidiol) and lesser studied minor phytocannabinoids, from nonclinical to clinical research. We pay particular attention to the areas where evidence is well established, including analgesic effects after acute exposures and neurocognitive risks after acute and chronic use. In addition, drug development considerations for cannabinoids as therapeutic agents within the United States are reviewed. The proposed clinical study design considerations encourage methodological standards for greater scientific rigor and reproducibility to ultimately extend our knowledge of the risks and benefits of cannabinoids for patients and providers. SIGNIFICANCE STATEMENT: This work provides a review of prior research related to phytocannabinoids, including therapeutic potential and known risks in the context of drug development within the United States. We also provide study design considerations for future cannabinoid drug development.

Abnormal structural covariance networks in young adults with recent cannabis use

BACKGROUND

Recent cannabis use (RCU) exerts adverse effects on the brain. However, the effect of RCU on structural covariance networks (SCNs) is still unclear. This retrospective cross-sectional study aimed to explore the effects of RCU on SCNs in young adults in terms of whole cerebral cortical thickness (CT) and cortical surface area (CSA).

METHODS

A total of 117 participants taking tetrahydrocannabinol (RCU group) and 896 participants not using cannabis (control group) were included in this study. All participants underwent MRI scanning following urinalysis screening, after which FreeSurfer 5.3 was used to calculate the CT and CSA, and SCNs matrices were constructed by Brain Connectivity Toolbox. Subsequently, the global and nodal network measures of the SCNs were computed based on these matrices. A nonparametric permutation test was used to investigate the group differences by Matlab.

RESULTS

Regarding global network measures of CT, young adults with RCU exhibited altered small-worldness (P = 0.020) and clustering coefficient (P = 0.031) compared to controls, whereas there were no significant group differences in terms of SCNs constructed with CSA. Additionally, SCNs based on CT and CSA displayed abnormal nodal degree, nodal efficiency, and nodal betweenness centrality in vital brain regions of the triple network, including the dorsolateral and ventrolateral prefrontal cortex, and anterior cingulate cortex.

CONCLUSION

The effects of RCU on brain structure in young adults can be detected by SCNs, in which structural abnormalities in the triple network are dominant, indicating that RCU can be detrimental to brain function.

Adolescent substance use initiation and long-term neurobiological outcomes: insights, challenges and opportunities

The increased frequency of risk taking behavior combined with marked neuromaturation has positioned adolescence as a focal point of research into the neural causes and consequences of substance use. However, little work has provided a summary of the links between adolescent initiated substance use and longer-term brain outcomes. Here we review studies exploring the long-term effects of adolescent-initiated substance use with structural and microstructural neuroimaging. A quarter of all studies reviewed conducted repeated neuroimaging assessments. Long-term alcohol use, as well as tobacco use were consistently associated with smaller frontal cortices and altered white matter microstructure. This association was mostly observed in the ACC, insula and subcortical regions in alcohol users, and for the OFC in tobacco users. Long-term cannabis use was mostly related to altered frontal cortices and hippocampal volumes. Interestingly, cannabis users scanned more years after use initiation tended to show smaller measures of these regions, whereas those with fewer years since initiation showed larger measures. Long-term stimulant use tended to show a similar trend as cannabis in terms of years since initiation in measures of the putamen, insula and frontal cortex. Long-term opioid use was mostly associated with smaller subcortical and insular volumes. Of note, null findings were reported in all substance use categories, most often in cannabis use studies. In the context of the large variety in study designs, substance use assessment, methods, and sample characteristics, we provide recommendations on how to interpret these findings, and considerations for future studies.

The use and potential abuse of psychoactive plants in southern Africa: an overview of evidence and future potential

Background

Most Bantu ethnic groups in southern Africa utilize indigenous herbal medicines, some of which have psychoactive properties. Traditional medical practitioners (TMPs) commonly use them not only for divinatory purposes but to treat and manage mental and other illnesses. Unfortunately, the research on their results, risks, and benefits do not align. Little is known about their potential abuse among TMPs and community members in southern Africa. Herbal medicines are complex because whole plants are sometimes used, unlike in other treatments which use only one active ingredient. However, if the key mechanisms of action of these ethnomedicinal plants can be identified through socio-pharmacological research, useful botanical agents can be developed. A review of socio-pharmacological studies to evaluate the consequences of exposure to ethnomedicinal plants with psychoactive properties was conducted with the aim of identifying harm reduction strategies and investigating how the plants could be developed into useful botanicals.

Method

The search methods involved retrieval of records from PubMed/MEDLINE, Embase, Web of Science, Dissertations and Theses Global, and OpenGrey. The English language and human subjects were used as filters. In addition, some information was obtained from TMPs and community members.

Results

The following psychoactive plants were found to be commonly used or abused: Boophone disticha, Cannabis sativa, Datura stramonium, Leonotis leonurus, Psilocybe cubensis, and Sceletium tortuosum. The commercialization of Cannabis, L. leonurus, S. tortuosum, and Aspalathus is growing fast. The abuse liability of B. disticha, D. stramonium, and P. cubensis appears not to be appreciated. Five countries were found to have TMP policies and three with TMP Councils.

Conclusion

TMPs in the region are aware of the CNS effects of the identified psychoactive plants which can be explored further to develop therapeutic agents. There is a need to work closely with TMPs to reduce harm from the abuse of these plants.

Medical cannabis for children: Evidence and recommendations

Interest in using cannabis products for a medical purpose in children under the age of 18 years is increasing. There are many medical cannabis products available that can include cannabidiol (CBD) or delta-9-tetrahydrocannabinol (THC), or both. Despite many therapeutic claims, there are few rigorous studies to inform the dosing, safety, and efficacy of medical cannabis in paediatric clinical practice. This statement reviews the current evidence and provides recommendations for using medical cannabis in children. Longer-term (2-year) reports support the sustained tolerability and efficacy of cannabidiol therapy for patients with Lennox-Gastaut and Dravet syndromes. CBD-enriched cannabis extracts containing small amounts of THC have been evaluated in a small number of paediatric patients, and further research is needed to inform clinical practice guidelines. Given the widespread use of medical cannabis in Canada, paediatricians should be prepared to engage in open, ongoing discussions with families about its potential benefits and risks, and develop individualized plans that monitor efficacy, reduce harms, and mitigate drug-drug interactions.

Les données probantes et les recommandations sur le cannabis à des fins médicales chez les enfants

L'intérêt envers l'utilisation des produits du cannabis à des fins médicales chez les enfants de moins de 18 ans augmente. De nombreux produits du cannabis à des fins médicales contiennent du cannabidiol, du delta-9-tétrahydrocannabinol ou ces deux produits. Malgré les nombreuses prétentions thérapeutiques, peu d'études rigoureuses guident la posologie, l'innocuité et l'efficacité du cannabis à des fins médicales en pédiatrie clinique. Le présent document de principes passe en revue les données probantes à jour et expose les recommandations sur l'utilisation du cannabis à des fins médicales chez les enfants. Les rapports à plus long terme (deux ans) souscrivent à la tolérabilité et à l'efficacité soutenues d'un traitement au cannabidiol chez les patients ayant le syndrome de Lennox-Gastaut ou le syndrome de Dravet. Les extraits de cannabis enrichis de cannabidiol qui renferment de petites quantités de delta-9-tétrahydrocannabinol ont été évalués auprès d'un petit nombre de patients d'âge pédiatrique, et d'autres recherches devront être réalisées pour éclairer les guides de pratique clinique. Étant donné l'utilisation répandue du cannabis à des fins médicales au Canada, les pédiatres devraient être prêts à participer à des échanges ouverts et continus avec les familles au sujet de ses avantages potentiels et de ses risques, ainsi qu'à préparer des plans individuels en vue d'en surveiller l'efficacité, de réduire les méfaits et de limiter les interactions médicamenteuses.

Exposure to Δ9-tetrahydrocannabinol leads to a rise in caspase-3, morphological changes in microglial, and astrocyte reactivity in the cerebellum of rats

The present study aimed to elucidate the effect of 10 mg/kg Δ9-tetrahydrocannabinol (THC) on cerebellar neuronal and glial morphology, apoptosis and inflammatory gene expression using a series of histological assays including stereology, Sholl analysis, immunofluorescence and real-time qPCR in male Wistar rats. A decrease in the number of Purkinje neurons and the thickness of the granular layer in the cerebellum was reported in THC-treated rats. Increased expression of Iba-1 and arborization of microglial processes were evidence of microgliosis and morphological changes in microglia. In addition, astrogliosis and changes in astrocyte morphology were other findings associated with THC administration. THC also led to an increase in caspase-3 positive cells and a decrease in autophagy and inflammatory gene expression such as mTOR, BECN1 and LAMP2. However, there were no significant changes in the volume of molecular layers and white matter, the spatial arrangement of granular layers and white matter, or the spatial arrangement of granular layers and white matter in the cerebellum. Taken together, our data showed both neuroprotective and neurodegenerative properties of THC in the cerebellum, which require further study in the future.

Framing substance use as "recreational" is neither accurate nor helpful for prevention purposes

This debate paper discusses six reasons why the term "recreational substance use" should be avoided. (1) Social norms and beliefs are drivers of behavior; therefore, the normalized use of the term conveys injunctive norms of a fully socially acceptable substance. Injunctive norms are the most important drivers of initiation into substance use. (2) The illusion of being in control, suggesting that if consumed for leisure and recreation it can easily be controlled; (3) Idealized social representations that fuel an idealized image of an alternative glamourous or mindful consumption culture; (4) Downplaying potential harms; (5) The implicit promise of everyday pleasure, the ever-growing potency of cannabis products does not fit the narrative of its use for recreation; (6) Industry as a trojan horse branding discourse of the concept of medical cannabis to normalize the image of non-medical use: to complement "therapeutic" with "recreational". "Recreational use" is a subjective ill-defined term. This debate paper aims to find a better terminological solution, honestly denominating with a neutral, unbiased, and objective connotation what is now called "recreational use". Thus, we propose using the term "non-therapeutic" use.

The causal link between cardiometabolic risk factors and gray matter atrophy: An exploratory study

Although gray matter atrophy is commonly observed with aging, it is highly variable, even among healthy people of the same age. This raises the question of what other factors may contribute to gray matter atrophy. Previous studies have reported that risk factors for cardiometabolic diseases are associated with accelerated brain aging. However, these studies were primarily based on standard correlation analyses, which do not unveil a causal relationship. While randomized controlled trials are typically required to investigate true causality, in this work, we investigated an alternative method by exploring data-driven causal discovery and inference techniques on observational data. Accordingly, this feasibility study used clinical and quantified gray matter volume data from 22,793 subjects from the UK biobank cohort without any known neurological disease. Our method identified that age, sex, body mass index (BMI), body fat percentage (BFP), and smoking exhibit a causal relationship with gray matter volume. Interventions on the causal network revealed that higher BMI and BFP values significantly increased the chance of gray matter atrophy in males, whereas this was not the case in females.

Deterrence effect of penalties upon adolescent cannabis use

OBJECTIVE

Penalties are used in an effort to curtail drug use by citizens in most societies. There are growing calls for a reduction or elimination of such penalties. Deterrence theory suggests that use should increase if penalties reduce and vice versa. We sought to examine the relationship between changes to penalties for drug possession and adolescent cannabis use.

METHOD

Ten instances of penalty change occurred in Europe between 2000 and 2014, seven of which involved penalty reduction and three involved penalty increase. We conducted a secondary analysis of a series of cross-sectional surveys of 15-16-year-old school children, the ESPAD surveys, which are conducted every four years. We focused on past month cannabis use. We anticipated that an eight-year time span before and after each penalty change would yield two data points either side of the change. A simple trend line was fitted to the data points for each country.

RESULTS

In eight cases, the trend slope in past month cannabis use was in the direction predicted by deterrence theory, the two exceptions being the UK policy changes. Using the principals of binomial distributions, the likelihood of this happening by chance is 56/1024 = 0.05. The median change in the baseline prevalence rate was by 21%.

CONCLUSIONS

The science seems far from settled on this issue. There remains a distinct possibility that reducing penalties could contribute to small increases in adolescent cannabis use and consequently increase cannabis-related harms. This possibility should be considered in any political decision-making influencing drug policy changes.

Brain Anatomical Alterations in Young Cannabis Users: Is it All Hype? A Meta-Analysis of Structural Neuroimaging Studies

Introduction: Cannabis use has a high prevalence in young youth and is associated with poor psychosocial outcomes. Such outcomes have been ascribed to the impact of cannabis exposure on the developing brain. However, findings from individual studies of volumetry in youth cannabis users are equivocal. Objectives: Our primary objective was to systematically review the evidence on brain volume differences between young cannabis users and nonusers aged 12-26 where profound neuromaturation occurs, accounting for the role of global brain volumes (GBVs). Our secondary objective was to systematically integrate the findings on the association between youth age and volumetry in youth cannabis users. Finally, we aimed to evaluate the quality of the evidence. Materials and Methods: A systematic search was run in three databases (PubMed, Scopus, and PsycINFO) and was reported using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We run meta-analyses (with and without controlling for GBV) of brain volume differences between young cannabis users and nonusers. We conducted metaregressions to explore the role of age on volumetric differences. Results: Sixteen studies were included. The reviewed samples included 830 people with mean age 22.5 years (range 14-26 years). Of these, 386 were cannabis users (with cannabis use onset at 15-19 years) and 444 were controls. We found no detectable group differences in any of the GBVs (intracranium, total brain, total white matter, and total gray matter) and regional brain volumes (i.e., hippocampus, amygdala, orbitofrontal cortex, and total cerebellum). Age and cannabis use level did not predict (standardized mean) volume group differences in metaregression. We found little evidence of publication bias (Egger's test p>0.1). Conclusions: Contrary to evidence in adult samples (or in samples mixing adults and youth), previous single studies in young cannabis users, and meta-analyses of brain function in young cannabis users, this early evidence suggests nonsignificant volume differences between young cannabis users and nonusers. While prolonged and long-term exposure to heavy cannabis use may be required to detect gross volume alterations, more studies in young cannabis users are needed to map in detail cannabis-related neuroanatomical changes.

Prefrontal cortex and putamen grey matter alterations in cannabis and tobacco users

BACKGROUND

Previous magnetic resonance imaging studies in regular cannabis users report altered grey matter volume (GMV) in brain regions, including the prefrontal cortex (PFC), putamen and hippocampus. However, most studies have tended to recruit recreational users with high levels of cannabis use, and have not controlled for the possible confounding effects of tobacco use. We attempt to address these limitations in the present study.

METHODS

We acquired volumetric images in sex, age and IQ-matched groups of (1) regular Cannabis users who also smoke Tobacco cigarettes ('CT'; n = 33), (2) non-cannabis-using Tobacco cigarette smokers ('T'; n = 19) and (3) non-cannabis/tobacco-using Controls ('C'; n = 35). GMV in bilateral PFC, putamen and hippocampal regions was compared across groups. We also examined the associations between GMV differences and levels of cannabis and tobacco use, measures of intellectual function, and of depression, anxiety and stress.

RESULTS

Relative to controls, both CT and T groups showed lower GMV in the left inferior frontal gyrus, and greater GMV in the putamen. In addition, lower GMV in the right frontal pole in the CT group (but not the T group) was associated with lifetime cannabis use, but not with cigarette use.

CONCLUSIONS

Regular cannabis users who also smoked tobacco cigarettes showed altered GMV patterns relative to controls. However, a similar pattern of GMV differences was also seen between regular tobacco users that did not use cannabis. Further research is needed to disentangle the effects of cannabis and tobacco use on brain structure.

Consensus paper of the WFSBP task force on cannabis, cannabinoids and psychosis

OBJECTIVES

The liberalisation of cannabis laws, the increasing availability and potency of cannabis has renewed concern about the risk of psychosis with cannabis.

METHODS

The objective of the WFSBP task force was to review the literature about this relationship.

RESULTS

Converging lines of evidence suggest that exposure to cannabis increases the risk for psychoses ranging from transient psychotic states to chronic recurrent psychosis. The greater the dose, and the earlier the age of exposure, the greater the risk. For some psychosis outcomes, the evidence supports some of the criteria of causality. However, alternate explanations including reverse causality and confounders cannot be conclusively excluded. Furthermore, cannabis is neither necessary nor sufficient to cause psychosis. More likely it is one of the multiple causal components. In those with established psychosis, cannabis has a negative impact on the course and expression of the illness. Emerging evidence also suggests alterations in the endocannabinoid system in psychotic disorders.

CONCLUSIONS

Given that exposure to cannabis and cannabinoids is modifiable, delaying or eliminating exposure to cannabis or cannabinoids, could potentially impact the rates of psychosis related to cannabis, especially in those who are at high risk for developing the disorder.

Detection of vaping, cannabis use, and hazardous prescription opioid use among adolescents

There has been a global surge in adolescents' use of electronic nicotine delivery systems (vaping), cannabis (vaped and edible), and prescription opioids, collectively termed ECPO. The nature of ECPO use can make it difficult to detect due to few obvious immediate physical and behavioural signs, as well as subtle long-term effects that allow adolescents to transition from initial exploration into hazardous ECPO use without easy detection by care providers. Here, we address the nature of the presentation of ECPO use in adolescents (roughly age 13-18 years), including challenges in detecting use and related complications, which affect screening, prevention, and intervention. We begin by reviewing empirical data on these difficult to detect effects in adolescents, including acute effects at cellular and neural levels and long-term neurocognitive and developmental changes that precede outwardly detectable physical signs. We then provide concrete approaches for providers to screen for ECPO use in adolescents even in the absence of overt physical and behavioural symptoms. Finally, we conclude with direct practice recommendations for prevention and intervention.

Individuals with cannabis use are associated with widespread morphological alterations in the subregions of the amygdala, hippocampus, and pallidum

BACKGROUND

Cannabis is the most frequently used illicit drug worldwide. Although multiple structural MRI studies of individuals with cannabis use (CB) have been undertaken, the reports of the volume alterations in the amygdala, hippocampus, and pallidum are not consistent. This study aims to detect subregion-level morphological alterations, analyze the correlation areas with cannabis usage characteristics, and gain new insights into the neuro mechanisms of CB.

METHODS

By leveraging the novel surface-based subcortical morphometry method, 20 CB and 22 age- and sex-matched healthy controls (HC) were included to explore their volumetric and morphological differences in the three subcortical structures. Afterward, the correlation analysis between surface morphological eigenvalues and cannabis usage characteristics was performed.

RESULTS

Compared with volumetric measures, the surface-based subcortical morphometry method detected more significant global morphological deformations in the left amygdala, right hippocampus, and right pallidum (overall-p < 0.05, corrected). More obvious morphological alterations (atrophy or expansion) were observed in specific subregions (vertex-based p-value<0.05, uncorrected) of the three subcortical structures. Both positive and negative subregional correlation areas were reported by the correlation analysis.

CONCLUSIONS

The current study illuminated new pathophysiologic mechanisms in the amygdala, hippocampus, and pallidum at the subregion level, which may inform the subsequent smaller-scale CB research.

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.

Aberrant hippocampal shape development in young adults with heavy cannabis use: Evidence from a longitudinal study

Cannabis is one of the most commonly used illicit drugs globally. Mounting evidence indicates that cannabis use, particularly consumption during young adulthood, is related to adverse mental and behavioral outcomes and an increased risk of the onset and relapse of psychosis. However, the neuromechanism underpinnings of heavy cannabis use (HCU) in young adults remain largely unknown, and no study has yet investigated the development of hippocampal shape in young adults with HCU. Twenty young adults with HCU and 22 matched non-cannabis-use healthy controls (HCs) were enrolled. Neuroimaging scanning and clinical assessments for all participants were performed at baseline (BL) and 3-year follow-up (FU). The vertex-wise shape analysis was conducted to investigate aberrant hippocampal shape development in young adults with HCU. Aberrant shape development pattern of the hippocampus was observed in young adults with HCU. There was no significant difference in hippocampal shape between the groups at BL, but young adults with HCU at FU exhibited significant shape atrophy of the right dorsal anterior hippocampus related to HCs. In addition, there was a significantly lower growth rate of the right hippocampal shape. Furthermore, there were significant associations of heavy cannabis use, as indicated by the age at onset first and frequent cannabis use, with the growth rate of hippocampal shape in young adults with HCU. The aberrant hippocampal shape development may reflect the effect of heavy cannabis use on young adults and it may be a potential target for heavy cannabis use treatment for young adults.

Associations of childhood sociability and responsibility with cannabis use trajectories during adolescence: results from a prospective population-based birth cohort study

This study aims to identify distinct trajectories of cannabis use during adolescence and examine whether Sociability (ability to relate to others) and Responsibility (ability to integrate a community setting) during childhood are associated with these trajectories, accounting for individual and familial confounders. Population-based cohort study (1998-2019): 1511 children from the Quebec Longitudinal Study of Child Development were followed between ages 5 months and 19 years. We identified developmental trajectories of adolescent cannabis use (assessed biyearly between ages 12 and 19 years) using a group-based trajectory model. We performed multinomial regression analyses to estimate the association between childhood Sociability and Responsibility assessed yearly between ages 6 and 12 years, and cannabis use trajectories. At 19 years, 62.8% (807/1286) of adolescents had used cannabis at least once in their lifetime, 44.2% had used at least once in the past 12 months (504/1140), and 6.8% were reporting daily use (77/1140). We identified three cannabis use trajectories: nonusers (n = 577, 38.2%), late users (n = 690, 45.7%; mean age of initiation: 16.2 ± 1.6), and early users (n = 244, 16.2%; mean age of initiation: 14.1 ± 1.3). Compared with Nonusers, children with low Sociability had a lower risk for late (OR, 0.43; 95 CI 0.27; 0.68) and early (OR, 0.22; 95 CI 0.12; 0.41) cannabis use. Children with low Responsibility were at higher risk of being Early users (OR, 2.23; 95 CI 1.13; 4.37) but not Late users (OR, 1.20; 95 CI 0.71; 2.03). Understanding the multiple dimensions of social skills and their association with cannabis use trajectories may help improve the effectiveness of evidence-based prevention strategies.

How do cannabis users mentally travel in time? Evidence from an fMRI study of episodic future thinking

RATIONALE

Episodic future thinking (EFT) is a cognitive function that allows individuals to imagine novel experiences that may happen in the future. Prior studies show that EFT is impaired in different groups of substance users. However, there is no evidence regarding the neurobiological mechanisms of EFT in cannabis users.

OBJECTIVES

We aimed to compare brain activations of regular cannabis users and non-using controls during an EFT fMRI task. Exploratory analyses were also conducted to investigate the association between EFT and cannabis use variables (e.g., duration of use, age onset, frequency of use).

METHODS

Twenty current cannabis users and 22 drug-naïve controls underwent an fMRI scanning session while completing a task involving envisioning future-related events and retrieval of past memories as a control condition. The EFT fMRI task was adapted from the autobiographical interview and composed of 20 auditory cue sentences (10 cues for past and 10 cues for future events). Participants were asked to recall a past or generate a future event, in response to the cues, and then rate their vividness after each response.

RESULTS

We found that cannabis users compared to non-user controls had lower activation within the cerebellum, medial and superior temporal gyrus, lateral occipital cortex, and occipital fusiform gyrus while envisioning future events. Cannabis users rated the vividness of past events significantly lower than non-users (P < 0.005). There were marginal group differences for rating the vividness of future events (P = 0.052). Significant correlations were also found between the medial and superior temporal gyrus activities and behavioral measures of EFT and episodic memory.

CONCLUSIONS

Cannabis users, compared to drug-naïve controls, have lower brain activation in EFT relevant regions. Thus, any attempts to improve aberrant EFT performance in cannabis users may benefit from EFT training.

Systematic review of structural and functional neuroimaging studies of cannabis use in adolescence and emerging adulthood: evidence from 90 studies and 9441 participants

Cannabis use peaks in adolescence, and adolescents may be more vulnerable to the neural effects of cannabis and cannabis-related harms due to ongoing brain development during this period. In light of ongoing cannabis policy changes, increased availability, reduced perceptions of harm, heightened interest in medicinal applications of cannabis, and drastic increases in cannabis potency, it is essential to establish an understanding of cannabis effects on the developing adolescent brain. This systematic review aims to: (1) synthesize extant literature on functional and structural neural alterations associated with cannabis use during adolescence and emerging adulthood; (2) identify gaps in the literature that critically impede our ability to accurately assess the effect of cannabis on adolescent brain function and development; and (3) provide recommendations for future research to bridge these gaps and elucidate the mechanisms underlying cannabis-related harms in adolescence and emerging adulthood, with the long-term goal of facilitating the development of improved prevention, early intervention, and treatment approaches targeting adolescent cannabis users (CU). Based on a systematic search of Medline and PsycInfo and other non-systematic sources, we identified 90 studies including 9441 adolescents and emerging adults (n = 3924 CU, n = 5517 non-CU), which provide preliminary evidence for functional and structural alterations in frontoparietal, frontolimbic, frontostriatal, and cerebellar regions among adolescent cannabis users. Larger, more rigorous studies are essential to reconcile divergent results, assess potential moderators of cannabis effects on the developing brain, disentangle risk factors for use from consequences of exposure, and elucidate the extent to which cannabis effects are reversible with abstinence. Guidelines for conducting this work are provided.

Pattern of predictive features of continued cannabis use in patients with recent-onset psychosis and clinical high-risk for psychosis

Continued cannabis use (CCu) is an important predictor for poor long-term outcomes in psychosis and clinically high-risk patients, but no generalizable model has hitherto been tested for its ability to predict CCu in these vulnerable patient groups. In the current study, we investigated how structured clinical and cognitive assessments and structural magnetic resonance imaging (sMRI) contributed to the prediction of CCu in a group of 109 patients with recent-onset psychosis (ROP). We tested the generalizability of our predictors in 73 patients at clinical high-risk for psychosis (CHR). Here, CCu was defined as any cannabis consumption between baseline and 9-month follow-up, as assessed in structured interviews. All patients reported lifetime cannabis use at baseline. Data from clinical assessment alone correctly classified 73% (p < 0.001) of ROP and 59 % of CHR patients. The classifications of CCu based on sMRI and cognition were non-significant (ps > 0.093), and their addition to the interview-based predictor via stacking did not improve prediction significantly, either in the ROP or CHR groups (ps > 0.065). Lower functioning, specific substance use patterns, urbanicity and a lack of other coping strategies contributed reliably to the prediction of CCu and might thus represent important factors for guiding preventative efforts. Our results suggest that it may be possible to identify by clinical measures those psychosis-spectrum patients at high risk for CCu, potentially allowing to improve clinical care through targeted interventions. However, our model needs further testing in larger samples including more diverse clinical populations before being transferred into clinical practice.

Disrupted Resting State Attentional Network Connectivity in Adolescent and Young Adult Cannabis Users following Two-Weeks of Monitored Abstinence

Background. Numerous neuropsychological studies have shown that cannabis use during adolescence and young adulthood led to deficits in sustained and selective attention. However, few studies have examined functional connectivity in attentional networks among young cannabis users, nor have characterized relationships with cannabis use patterns following abstinence. Methods. Differences in resting state functional connectivity (RSFC) within the dorsal (DAN) and ventral (VAN) attention networks were examined in 36 adolescent and young adult cannabis users and 39 non-substance using controls following two weeks of monitored abstinence. Observed connectivity differences were then correlated with past-year and lifetime cannabis use, length of abstinence, age of regular use onset, and Cannabis Use Disorder symptoms (CUD). Results. After controlling for alcohol and nicotine use, cannabis users had lower RSFC within the DAN network, specifically between right inferior parietal sulcus and right anterior insula, as well as white matter, relative to controls. This region was associated with more severe cannabis use measures, including increased lifetime cannabis use, shorter length of abstinence, and more severe CUD symptoms. Conclusions. Findings demonstrate that regular cannabis use by adolescents and young adults is associated with subtle differences in resting state connectivity within the DAN, even after two weeks of monitored abstinence. Notably, more severe cannabis use markers (greater lifetime use, CUD symptoms, and shorter abstinence) were linked with this reduced connectivity. Thus, findings support public policy aimed at reducing and delaying cannabis use and treatments to assist with sustained abstinence. Future longitudinal studies are needed to investigate causation.

Interaction of sex and cannabis in adult in vivo brain imaging studies: A systematic review

Cannabis has been shown to cause structural and functional neurocognitive changes in heavy users. Cannabis use initiation aligns with brain development trajectories; therefore, it is imperative that the potential neurological implications of cannabis use are understood. Males and females reach neurodevelopmental milestones at different rates making it necessary to consider biological sex in all cannabis and brain-based research. Through use of a systamatic review in accordance with PRISMA guidelines, we aimed to understand the interaction between biological sex and cannabis use on brain-based markers. In total, 18 articles containing a sex-based analysis of cannabis users were identified. While the majority of studies (n = 11) reported no sex by cannabis use interactions on brain-based markers, those that reported findings (n = 8) suggest females may be more susceptible to cannabis' neurotoxic effects. Unfortunately, a large portion of the literature was excluded due to no sex-based analysis. In addition, studies that reported no sex differences often contained a reduced number of females which may result in some studies being underpowered for sex-based analyses, making it difficult to draw firm conclusions. Suggestions to improve cannabis and sex-based reseach are proposed.

Frequent teenage cannabis use: Prevalence across adolescence and associations with young adult psychopathology and functional well-being in an urban cohort

BACKGROUND

Amidst cannabis legalization efforts and laws, we do not fully understand how the youngest frequent cannabis users fare during young adulthood. This study aims to 1) examine the prevalence of cannabis use during adolescence, and 2) investigate links of frequent (i.e., weekly or daily) teenage cannabis use with psychopathology and functional well-being at age 20-compared to no or occasional use.

METHODS

Data came from a prospective-longitudinal cohort study (assessments from 2004 to 2018, from ages 7-20) in an urban setting (N = 1482). Substance use was assessed with self-reports between ages 13 and 20. At age 20, participants reported on psychopathology (psychotic symptoms, problematic substance use, aggression, and internalizing symptoms) and functional well-being (delinquency, financial difficulties, social exclusion, general well-being, and not being in education, employment, or training). Covariates were based on self-, parent-, teacher-, and behavioral measures.

FINDINGS

Almost one in five adolescents had used cannabis frequently between ages 13 and 17 (26.6% of males, 9.8% of females). Adjusting nearly 20 potential confounders, frequent teenage cannabis use was associated with age 20 problematic substance use and poorer functional well-being compared to the no cannabis use and the occasional use groups. Frequent teenage cannabis use was more consistently associated with age 20 functional outcomes compared to frequent teenage nicotine or alcohol use.

CONCLUSIONS

Frequent teenage cannabis use was common and associated with problematic substance use, more delinquency, and poorer functional well-being at age 20. Accordingly, frequent teenage cannabis users could experience increased difficulties in mastering the transitions of young adulthood.

Neuropsychological and neurophysiological predictors and consequences of cannabis and illicit substance use during neurodevelopment: a systematic review of longitudinal studies

Adolescence and early adulthood are crucial periods of neurodevelopment characterised by functional, structural, and cognitive maturation, which helps prepare young people for adulthood. This systematic review of longitudinal studies aims to delineate neural predictors from neural consequences of cannabis and illicit substance use, as well as investigate the potential for the developing brain (at ages 10-25 years) to recover after damage. Five databases were searched to yield a total of 38 eligible studies, with some assessing multiple outcome techniques, including 22 neuroimaging, two neurophysiological, and 22 neuropsychological findings. High-quality evidence suggested that delayed or irregular neurodevelopment in executive functioning, particularly emotional perception, might predispose young people to higher frequency substance use. There was evidence of functional, structural, and cognitive deficits proceeding substance use, with harm potentially dependent on the frequency of use and recovery potentially dependent on the duration of use. Identifying aberrant neurodevelopment in young people is crucial for preventing substance use-related harm.

Association between age of cannabis initiation and gray matter covariance networks in recent onset psychosis

Cannabis use during adolescence is associated with an increased risk of developing psychosis. According to a current hypothesis, this results from detrimental effects of early cannabis use on brain maturation during this vulnerable period. However, studies investigating the interaction between early cannabis use and brain structural alterations hitherto reported inconclusive findings. We investigated effects of age of cannabis initiation on psychosis using data from the multicentric Personalized Prognostic Tools for Early Psychosis Management (PRONIA) and the Cannabis Induced Psychosis (CIP) studies, yielding a total sample of 102 clinically-relevant cannabis users with recent onset psychosis. GM covariance underlies shared maturational processes. Therefore, we performed source-based morphometry analysis with spatial constraints on structural brain networks showing significant alterations in schizophrenia in a previous multisite study, thus testing associations of these networks with the age of cannabis initiation and with confounding factors. Earlier cannabis initiation was associated with more severe positive symptoms in our cohort. Greater gray matter volume (GMV) in the previously identified cerebellar schizophrenia-related network had a significant association with early cannabis use, independent of several possibly confounding factors. Moreover, GMV in the cerebellar network was associated with lower volume in another network previously associated with schizophrenia, comprising the insula, superior temporal, and inferior frontal gyrus. These findings are in line with previous investigations in healthy cannabis users, and suggest that early initiation of cannabis perturbs the developmental trajectory of certain structural brain networks in a manner imparting risk for psychosis later in life.

Association of Cannabis Use During Adolescence With Neurodevelopment

IMPORTANCE

Animal studies have shown that the adolescent brain is sensitive to disruptions in endocannabinoid signaling, resulting in altered neurodevelopment and lasting behavioral effects. However, few studies have investigated ties between cannabis use and adolescent brain development in humans.

OBJECTIVE

To examine the degree to which magnetic resonance (MR) imaging-assessed cerebral cortical thickness development is associated with cannabis use in a longitudinal sample of adolescents.

DESIGN, SETTING, AND PARTICIPANTS

Data were obtained from the community-based IMAGEN cohort study, conducted across 8 European sites. Baseline data used in the present study were acquired from March 1, 2008, to December 31, 2011, and follow-up data were acquired from January 1, 2013, to December 31, 2016. A total of 799 IMAGEN participants were identified who reported being cannabis naive at study baseline and had behavioral and neuroimaging data available at baseline and 5-year follow-up. Statistical analysis was performed from October 1, 2019, to August 31, 2020.

MAIN OUTCOMES AND MEASURES

Cannabis use was assessed at baseline and 5-year follow-up with the European School Survey Project on Alcohol and Other Drugs. Anatomical MR images were acquired with a 3-dimensional T1-weighted magnetization prepared gradient echo sequence. Quality-controlled native MR images were processed through the CIVET pipeline, version 2.1.0.

RESULTS

The study evaluated 1598 MR images from 799 participants (450 female participants [56.3%]; mean [SD] age, 14.4 [0.4] years at baseline and 19.0 [0.7] years at follow-up). At 5-year follow-up, cannabis use (from 0 to >40 uses) was negatively associated with thickness in left prefrontal (peak: t785 = -4.87, cluster size = 1558 vertices; P = 1.10 × 10-6, random field theory cluster corrected) and right prefrontal (peak: t785 = -4.27, cluster size = 1551 vertices; P = 2.81 × 10-5, random field theory cluster corrected) cortices. There were no significant associations between lifetime cannabis use at 5-year follow-up and baseline cortical thickness, suggesting that the observed neuroanatomical differences did not precede initiation of cannabis use. Longitudinal analysis revealed that age-related cortical thinning was qualified by cannabis use in a dose-dependent fashion such that greater use, from baseline to follow-up, was associated with increased thinning in left prefrontal (peak: t815.27 = -4.24, cluster size = 3643 vertices; P = 2.28 × 10-8, random field theory cluster corrected) and right prefrontal (peak: t813.30 = -4.71, cluster size = 2675 vertices; P = 3.72 × 10-8, random field theory cluster corrected) cortices. The spatial pattern of cannabis-related thinning was associated with age-related thinning in this sample (r = 0.540; P < .001), and a positron emission tomography-assessed cannabinoid 1 receptor-binding map derived from a separate sample of participants (r = -0.189; P < .001). Analysis revealed that thinning in right prefrontal cortices, from baseline to follow-up, was associated with attentional impulsiveness at follow-up.

CONCLUSIONS AND RELEVANCE

Results suggest that cannabis use during adolescence is associated with altered neurodevelopment, particularly in cortices rich in cannabinoid 1 receptors and undergoing the greatest age-related thickness change in middle to late adolescence.

Relationships between age at first substance use and persistence of cannabis use and cannabis use disorder

Background

From a secondary prevention perspective, it is useful to know who is at greatest risk of progressing from substance initiation to riskier patterns of future use. Therefore, the aim of this study was to determine relationships between age at first use of alcohol, tobacco and cannabis and patterns of cannabis use, frequency of use and whether age of substance use onset is related to having a cannabis use disorder (CUD).

Methods

We analysed data from Ireland’s 2010/11 and 2014/15 National Drug Prevalence Surveys, which recruited 5134 and 7005 individuals respectively, aged 15 years and over, living in private households. We included only those people who reported lifetime cannabis use. Multinomial, linear and binary logistic regression analyses were used to determine relationships between age of substance use onset and patterns of cannabis use, frequency of use and having a CUD.

Results

When compared to former users, the odds of being a current cannabis user were found to be reduced by 11% (OR = 0.89; 95% CI: 0.83, 0.95) and 4% (OR = 0.96; 95% CI: 0.92, 1.00) for each year of delayed alcohol and cannabis use onset, respectively. Among current users, significant inverse linear relationships were noted, with increasing age of first use of tobacco (β = − 0.547; P < .001) and cannabis (β = − 0.634; P < .001) being associated with a decreased frequency of cannabis use within the last 30 days. The odds of having a CUD were found to be reduced by 14% (OR = 0.86; 95% CI: 0.78, 0.94) and 11% (OR = 0.89; 95% CI: 0.82, 0.98) for each year of delayed tobacco and cannabis use onset respectively in analyses which examined survey participants aged 15–34 years.

Conclusions

Among people who report past cannabis use, it is those with a more precocious pattern of early use of substances, including alcohol, and especially tobacco and cannabis, who are more likely to report ongoing, heavy and problematic cannabis use. Secondary prevention initiatives should prioritise people with a pattern of very early onset substance use.

Trait mindfulness and cannabis use-related factors in adolescents and young adults with frequent use

BACKGROUND

Mindfulness-based interventions (MBIs) are effective in adult substance-use treatment and may be helpful for adolescents and young adults (AYAs). One target of MBIs is to improve trait mindfulness, which has been associated with better lifestyle and health outcomes. To inform MBIs for reducing cannabis use in AYAs, we sought to identify how trait mindfulness was associated with cannabis-related problems and quit attempts, as well as with motivation to change use in youth who report frequent use. Methods: Participants aged 15-24 years using cannabis ≥ 3x/week were recruited from AYA clinics in a northeastern US city to participate in a cannabis-use intervention pilot, randomized trial. At baseline, we assessed cannabis-use history, problems associated with use, attempts to quit, and trait mindfulness. All participants were offered two sessions of motivational enhancement therapy, during which they rated motivation to quit cannabis. Regression analyses were conducted to assess associations between trait mindfulness and cannabis use-related problems, attempts to quit, and motivation to change. Results: Seventy participants, mean age 20.7 ± 1.9 years, enrolled. Sixty percent identified as female, 47% as Black non-Hispanic, and 31% as Hispanic. Participants started using cannabis at mean age 15.0 ± 2.8 years and were using ≥ 3x/week by 17.0 ± 2.3 years. Higher mindfulness scores were associated with fewer cannabis-related problems (p = 0.004) and fewer quit attempts (p = 0.035). The number of cannabis-related problems did not significantly mediate the relationship between mindfulness and quit attempts. Trait mindfulness did not predict motivation to change cannabis use. Conclusions: Among AYAs using cannabis frequently, higher trait mindfulness was associated with both fewer cannabis use--related problems and fewer quit attempts. Future research should assess whether trait mindfulness is an appropriate target for decreasing cannabis use and the utility of MBIs for reducing cannabis-use behaviors.

Exploring the impact of adolescent exposure to cannabinoids and nicotine on psychiatric risk: insights from translational animal models

Adolescence represents a highly sensitive period of mammalian neurodevelopment wherein critical synaptic and structural changes are taking place in brain regions involved in cognition, self-regulation and emotional processing. Importantly, neural circuits such as the mesocorticolimbic pathway, comprising the prefrontal cortex, sub-cortical mesolimbic dopamine system and their associated input/output centres, are particularly vulnerable to drug-related insults. Human adolescence represents a life-period wherein many individuals first begin to experiment with recreational drugs such as nicotine and cannabis, both of which are known to profoundly modulate neurochemical signalling within the mesocorticolimbic pathway and to influence both long-term and acute neuropsychiatric symptoms. While a vast body of epidemiological clinical research has highlighted the effects of adolescent exposure to drugs such as nicotine and cannabis on the developing adolescent brain, many of these studies are limited to correlative analyses and rely on retrospective self-reports from subjects, making causal interpretations difficult to discern. The use of pre-clinical animal studies can avoid these issues by allowing for precise temporal and dose-related experimental control over drug exposure during adolescence. In addition, such animal-based research has the added advantage of allowing for in-depth molecular, pharmacological, genetic and neuronal analyses of how recreational drug exposure may set up the brain for neuropsychiatric risk. This review will explore some of the advantages and disadvantages of these models, with a focus on the common, divergent and synergistic effects of adolescent nicotine and cannabis exposure on neuropsychiatric risk.

Which came first: Cannabis use or deficits in impulse control?

Impulse control deficits are often found to co-occur with substance use disorders (SUDs). On the one hand, it is well known that chronic intake of drugs of abuse remodels the brain with significant consequences for a range of cognitive behaviors. On the other hand, individual variation in impulse control may contribute to differences in susceptibility to SUDs. Both of these relationships have been described, thus leading to a "chicken or the egg" debate which remains to be fully resolved. Does impulsivity precede drug use or does it manifest as a function of problematic drug usage? The link between impulsivity and SUDs has been most strongly established for cocaine and alcohol use disorders using both preclinical models and clinical data. Much less is known about the potential link between impulsivity and cannabis use disorder (CUD) or the directionality of this relationship. The initiation of cannabis use occurs most often during adolescence prior to the brain's maturation, which is recognized as a critical period of development. The long-term effects of chronic cannabis use on the brain and behavior have started to be explored. In this review we will summarize these observations, especially as they pertain to the relationship between impulsivity and CUD, from both a psychological and biological perspective. We will discuss impulsivity as a multi-dimensional construct and attempt to reconcile the results obtained across modalities. Finally, we will discuss possible avenues for future research with emerging longitudinal data.

Therapeutic and toxicological aspects of the use of cannabis and cannabinoids in medicine

Abstract

The legalization of cannabis products for recreational and/or medical use means that our society is now clearly more open to its diffusion. Thus, it is particularly important for people to understand what is known about both the adverse health effects and the potential therapeutic benefits linked to cannabis. The evaluation of the benefit vs adverse effect of cannabis use is generally referred to its recreational use; however, medicinal cannabis is now authorized in several countries, and therefore, it has become a public safety issue. In this article, the acute and long-lasting consequences of recreational cannabis use as well as the therapeutic vs toxicological effect of medicinal cannabis will be summarized.

Graphic abstract

The Influence of Cannabis and Nicotine Co-use on Neuromaturation: A Systematic Review of Adolescent and Young Adult Studies

Accumulating evidence suggests that the use of cannabis and nicotine and tobacco-related products (NTPs) during the adolescent years has harmful effects on the developing brain. Yet, few studies have focused on the developing brain as it relates to the co-administration of cannabis and NTPs, despite the high prevalence rates of co-use in adolescence. This review aims to synthesize the existing literature on neurocognitive, structural neuroimaging, and functional neuroimaging outcomes associated with cannabis and NTP co-use. A systematic search of peer-reviewed articles resulted in a pool of 1107 articles. Inclusion criteria were 1) data-based study; 2) age range of 13 to 35 years or, for preclinical studies, nonadult subjects; 3) cannabis and NTP group jointly considered; and 4) neurocognitive, structural neuroimaging, or functional neuroimaging as an outcome measure. Twelve studies met inclusion criteria. Consistent with the literature, cannabis and nicotine were found to have independent effects on cognition. The available research on the co-use of cannabis and NTPs demonstrates a potential nicotine-related masking effect on cognitive deficits associated with cannabis use, yet there is little research on co-use and associations with neuroimaging indices. In neuroimaging studies, there is preliminary evidence for hippocampal volume differences in co-users and a lack of evidence for co-use differences related to nucleus accumbens activity during reward processing. Notably, no structural neuroimaging studies were found to examine the combined effects of nicotine and cannabis in adolescent-only populations. Further research, including longitudinal studies, is warranted to investigate the influence of cannabis and NTP co-use on maturation.

Age- and Sex-Related Cortical Gray Matter Volume Differences in Adolescent Cannabis Users: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies

Introduction: Adolescent-onset cannabis use is rising in the era of marijuana legalization. Recent imaging studies have identified neuroanatomical differences between adult cannabis users and controls that are more prominent in early-onset users. Other studies point to sex-dependent effects of cannabis. Methods: A systematic review following PRISMA guidelines and subsequent effect-size seed-based d mapping (SDM) meta-analyses were conducted to investigate relationships between age (across the 12-to-21-year-old developmental window), sex, and gray matter volume (GMV) differences between cannabis using (CU) and typically developing (TD) youth. Results: Our search identified 1,326 citations, 24 of which were included in a qualitative analysis. A total of 6 whole-brain voxel-based morphometry (VBM) studies comparing regional GMV between 357 CU [mean (SD) age = 16.68 (1.28); 71% male] and 404 TD [mean (SD) age = 16.77 (1.36); 63% male] youth were included in the SDM-meta-analysis. Meta-analysis of whole-brain VBM studies identified no regions showing significant GMV difference between CU and TD youth. Meta-regressions showed divergent effects of age and sex on cortical GMV differences in CU vs. TD youth. Age effects were seen in the superior temporal gyrus (STG), with older-aged CU youth showing decreased and younger-aged CU youth showing increased STG GMV compared to age-matched TD youth. Parallel findings in the STG were also observed in relation to duration of CU (years) in supplemental meta-regressions. Regarding sex effects, a higher proportion of females in studies was associated with increased GMV in the middle occipital gyrus in CU vs. TD youth. Conclusions: These findings suggest that GMV differences between CU and TD youth, if present, are subtle, and may vary as a function of age, cumulative cannabis exposure, and sex in young people. Whether age- and sex-related GMV differences are attributable to common predispositional factors, cannabis-induced neuroadaptive changes, or both warrant further investigation.

Intelligence quotient decline following frequent or dependent cannabis use in youth: a systematic review and meta-analysis of longitudinal studies

Previous systematic reviews and meta-analyses of cross-sectional data assessing the effect of cannabis on cognitive functioning and intelligence show inconsistent results. We hypothesized that frequent and dependent cannabis use in youth would be associated with Intelligence Quotient (IQ) decline. This study is a systematic review and meta-analysis. We searched Embase, PubMed and PsychInfo from inception to 24 January 2020. We included studies with non-treatment seeking samples and pre- and post-exposure measures of IQ. We requested data from authors if summary data was not available from published work. We preregistered our review with PROSPERO (ID no. CRD42019125624). We found seven cohort studies including 808 cases and 5308 controls. We found a significant effect for the association between frequent or dependent cannabis use in youth and IQ change, Cohen's d = -0.132 (95% CI -0.198 to -0.066) p < 0.001. Statistical heterogeneity between studies was also low at I2 = 0.2%. Study quality was moderate to high. This translates to an average decline of approximately 2 IQ points following exposure to cannabis in youth. Future studies should have longer periods of follow up to assess the magnitude of developmental impact.

Adverse effects of Δ9-tetrahydrocannabinol on neuronal bioenergetics during postnatal development

Ongoing societal changes in views on the medical and recreational roles of cannabis increased the use of concentrated plant extracts with a Δ⁹-tetrahydrocannabinol (THC) content of more than 90%. Even though prenatal THC exposure is widely considered adverse for neuronal development, equivalent experimental data for young age cohorts are largely lacking. Here, we administered plant-derived THC (1 or 5 mg/kg) to mice daily during P5–P16 and P5–P35 and monitored its effects on hippocampal neuronal survival and specification by high-resolution imaging and iTRAQ proteomics, respectively. We found that THC indiscriminately affects pyramidal cells and both cannabinoid receptor 1⁺ (CB₁R)⁺ and CB₁R^– interneurons by P16. THC particularly disrupted the expression of mitochondrial proteins (complexes I–IV), a change that had persisted even 4 months after the end of drug exposure. This was reflected by a THC-induced loss of membrane integrity occluding mitochondrial respiration and could be partially or completely rescued by pH stabilization, antioxidants, bypassed glycolysis, and targeting either mitochondrial soluble adenylyl cyclase or the mitochondrial voltage-dependent anion channel. Overall, THC exposure during infancy induces significant and long-lasting reorganization of neuronal circuits through mechanisms that, in large part, render cellular bioenergetics insufficient to sustain key developmental processes in otherwise healthy neurons.

Repeated THC exposure in juvenile mice compromises the limbic circuitry, with life-long impairment to the respiration of neurons.

The associations of comorbid substance use disorders and psychiatric conditions with adolescent brain structure and function: A review

Adolescence is a period of rapid neural and behavioral development that often precipitates substance use, substance use disorders (SUDs), and other psychopathology. While externalizing disorders have been closely linked to SUD epidemiologically, the comorbidity of internalizing disorders and SUD is less well understood. Neuroimaging studies can be used to measure structural and functional developments in the brain that mediate the relationship between psychopathology and SUD in adolescence. Externalizing disorders and SUD are both associated with structural and functional changes in the basal ganglia and prefrontal cortex in adolescence. The neural mechanisms underlying internalizing disorders and SUD are less clear, but evidence points to involvement of the amygdala and prefrontal cortex. We also highlight independent contributions of SUD, which may vary in certain ways by the substances assessed. A deeper understanding of the neural basis of the relationship between psychopathology and SUD will allow for more informed interventions in this critical developmental stage.

Community-Based Participatory Research: Engaging Youth to Provide Perspective on Risk and Protective Factors

BACKGROUND

The Pennsylvania Youth Survey (PAYS) is administered biennially to adolescents; it covers knowledge, attitudes, and behaviors about risk and protective factors.

PURPOSE

This study explored 8th, 10th, and 12th grade students' attitudes and beliefs about current trends regarding drugs, alcohol, and mental health.

METHODS

We asked persons a series of questions in semi-structured focus groups (102 participants) while they were being presented with the PAYS data.

RESULTS

Participants expressed significant insight on root causes of risk behaviors. They recommended a decreased emphasis on grades and class rank, and recommended addressing mental health stigma, educating about vaping and marijuana effects, and obtaining support from families, schools, and communities.

CONCLUSION

Youth expressed interest in being an integral part of the planning and decision-making efforts that impact them. Our results support the Whole School, Community, and Child (WSCC) model.

The endocannabinoid system in modulating fear, anxiety, and stress

The endocannabinoid system is widely expressed in the limbic system, prefrontal cortical areas, and brain structures regulating neuroendocrine stress responses, which explains the key role of this system in the control of emotions. In this review, we update recent advances on the function of the endocannabinoid system in determining the value of fear-evoking stimuli and promoting appropriate behavioral responses for stress resilience. We also review the alterations in the activity of the endocannabinoid system during fear, stress, and anxiety, and the pathophysiological role of each component of this system in the control of these protective emotional responses that also trigger pathological emotional disorders. In spite of all the evidence, we have not yet taken advantage of the therapeutic implications of this important role of the endocannabinoid system, and possible future strategies to improve the treatment of these emotional disorders are discussed.


Adolescent Substance Use and the Brain: Behavioral, Cognitive and Neuroimaging Correlates

Adolescence is an important ontogenetic period that is characterized by behaviors such as enhanced novelty-seeking, impulsivity, and reward preference, which can give rise to an increased risk for substance use. While substance use rates in adolescence are generally on a decline, the current rates combined with emerging trends, such as increases in e-cigarette use, remain a significant public health concern. In this review, we focus on the neurobiological divergences associated with adolescent substance use, derived from a cross-sectional, retrospective, and longitudinal studies, and highlight how the use of these substances during adolescence may relate to behavioral and neuroimaging-based outcomes. Identifying and understanding the associations between adolescent substance use and changes in cognition, mental health, and future substance use risk may assist our understanding of the consequences of drug exposure during this critical window.