Cannabis use in youth is associated with limited alterations in brain structure

Cells and Molecules Underpinning Cannabis-Related Variations in Cortical Thickness during Adolescence

During adolescence, cannabis experimentation is common, and its association with interindividual variations in brain maturation well studied. Cellular and molecular underpinnings of these system-level relationships are, however, unclear. We thus conducted a three-step study. First, we exposed adolescent male mice to Δ-9-tetrahydrocannabinol (THC) or a synthetic cannabinoid WIN 55,212-2 (WIN) and assessed differentially expressed genes (DEGs), spine numbers, and dendritic complexity in their frontal cortex. Second, in human (male) adolescents, we examined group differences in cortical thickness in 34 brain regions, using magnetic resonance imaging, between those who experimented with cannabis before age 16 (n = 140) and those who did not (n = 327). Finally, we correlated spatially these group differences with gene expression of human homologs of mouse-identified DEGs. The spatial expression of 13 THC-related human homologs of DEGs correlated with cannabis-related variations in cortical thickness, and virtual histology revealed coexpression patterns of these 13 genes with cell-specific markers of astrocytes, microglia, and a type of pyramidal cells enriched in dendrite-regulating genes. Similarly, the spatial expression of 18 WIN-related human homologs of DEGs correlated with group differences in cortical thickness and showed coexpression patterns with the same three cell types. Gene ontology analysis indicated that 37 THC-related human homologs are enriched in neuron projection development, while 33 WIN-related homologs are enriched in processes associated with learning and memory. In mice, we observed spine loss and lower dendritic complexity in pyramidal cells of THC-exposed animals (vs controls). Experimentation with cannabis during adolescence may influence cortical thickness by impacting glutamatergic synapses and dendritic arborization.

Daily Cannabidiol Administration for 10 Weeks Modulates Hippocampal and Amygdalar Resting-State Functional Connectivity in Cannabis Users: A Functional Magnetic Resonance Imaging Open-Label Clinical Trial

Introduction: Cannabis use is associated with brain functional changes in regions implicated in prominent neuroscientific theories of addiction. Emerging evidence suggests that cannabidiol (CBD) is neuroprotective and may reverse structural brain changes associated with prolonged heavy cannabis use. In this study, we examine how an ∼10-week exposure of CBD in cannabis users affected resting-state functional connectivity in brain regions functionally altered by cannabis use. Materials and Methods: Eighteen people who use cannabis took part in a ∼10 weeks open-label pragmatic trial of self-administered daily 200 mg CBD in capsules. They were not required to change their cannabis exposure patterns. Participants were assessed at baseline and post-CBD exposure with structural magnetic resonance imaging (MRI) and a functional MRI resting-state task (eyes closed). Seed-based connectivity analyses were run to examine changes in the functional connectivity of a priori regions-the hippocampus and the amygdala. We explored if connectivity changes were associated with cannabinoid exposure (i.e., cumulative cannabis dosage over trial, and plasma CBD concentrations and Δ9-tetrahydrocannabinol (THC) plasma metabolites postexposure), and mental health (i.e., severity of anxiety, depression, and positive psychotic symptom scores), accounting for cigarette exposure in the past month, alcohol standard drinks in the past month and cumulative CBD dose during the trial. Results: Functional connectivity significantly decreased pre-to-post the CBD trial between the anterior hippocampus and precentral gyrus, with a strong effect size (d=1.73). Functional connectivity increased between the amygdala and the lingual gyrus pre-to-post the CBD trial, with a strong effect size (d=1.19). There were no correlations with cannabinoids or mental health symptom scores. Discussion: Prolonged CBD exposure may restore/reduce functional connectivity differences reported in cannabis users. These new findings warrant replication in a larger sample, using robust methodologies-double-blind and placebo-controlled-and in the most vulnerable people who use cannabis, including those with more severe forms of Cannabis Use Disorder and experiencing worse mental health outcomes (e.g., psychosis, depression).

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.

Abnormal developmental of structural covariance networks in young adults with heavy cannabis use: a 3-year follow-up study

Heavy cannabis use (HCU) exerts adverse effects on the brain. Structural covariance networks (SCNs) that illustrate coordinated regional maturation patterns are extensively employed to examine abnormalities in brain structure. Nevertheless, the unexplored aspect remains the developmental alterations of SCNs in young adults with HCU for three years, from the baseline (BL) to the 3-year follow-up (FU). These changes demonstrate dynamic development and hold potential as biomarkers. A total of 20 young adults with HCU and 22 matched controls were recruited. All participants underwent magnetic resonance imaging (MRI) scans at both the BL and FU and were evaluated using clinical measures. Both groups used cortical thickness (CT) and cortical surface area (CSA) to construct structural covariance matrices. Subsequently, global and nodal network measures of SCNs were computed based on these matrices. Regarding global network measures, the BL assessment revealed significant deviations in small-worldness and local efficiency of CT and CSA in young adults with HCU compared to controls. However, no significant differences between the two groups were observed at the FU evaluation. Young adults with HCU displayed changes in nodal network measures across various brain regions during the transition from BL to FU. These alterations included abnormal nodal degree, nodal efficiency, and nodal betweenness in widespread areas such as the entorhinal cortex, superior frontal gyrus, and parahippocampal cortex. These findings suggest that the topography of CT and CSA plays a role in the typical structural covariance topology of the brain. Furthermore, these results indicate the effect of HCU on the developmental changes of SCNs in young adults.

The Effect of Oil-Based Cannabis Extracts on Metabolic Parameters and Microbiota Composition of Mice Fed a Standard and a High-Fat Diet

The prevalence of obesity and obesity-related pathologies is lower in frequent cannabis users compared to non-users. It is well established that the endocannabinoid system has an important role in the development of obesity. We recently demonstrated that prolonged oral consumption of purified Δ-9 Tetrahydrocannabinol (THC), but not of cannabidiol (CBD), ameliorates diet-induced obesity and improves obesity-related metabolic complications in a high-fat diet mouse model. However, the effect of commercially available medical cannabis oils that contain numerous additional active molecules has not been examined. We tested herein the effects of THC- and CBD-enriched medical cannabis oils on obesity parameters and the gut microbiota composition of C57BL/6 male mice fed with either a high-fat or standard diet. We also assessed the levels of prominent endocannabinoids and endocannabinoid-like lipid mediators in the liver. THC-enriched extract prevented weight gain by a high-fat diet and attenuated diet-induced liver steatosis concomitantly with reduced levels of the lipid mediators palmitoyl ethanolamide (PEA) and docosahexaenoyl ethanolamide (DHEA) in the liver. In contrast, CBD-enriched extract had no effect on weight gain, but, on the contrary, it even exacerbated liver steatosis. An analysis of the gut microbiota revealed that mainly time but not treatment exerted a strong effect on gut microbiota alterations. From our data, we conclude that THC-enriched cannabis oil where THC is the main constituent exerts the optimal anti-obesity effects.

Impact of Adolescent Cannabis Use on Neurocognitive and Brain Development

Research examining associations between frequent cannabis use in adolescence and brain-behavior outcomes has increased substantially over the past 2 decades. This review attempts to synthesize the state of evidence in this area of research while acknowledging challenges in interpretation. Although there is converging evidence that ongoing, frequent cannabis use in adolescence is associated with small reductions in cognitive functioning, there is still significant debate regarding the persistence of reductions after a period of abstinence. Similarly, there is controversy regarding the replicability of structural and functional neuroimaging findings related to frequent cannabis use in adolescence. Larger studies with informative designs are needed.

The Effect of Orally Administered Δ9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD) on Obesity Parameters in Mice

Prolonged cannabis users show a lower prevalence of obesity and associated comorbidities. In rodent models, Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD) from the plant Cannabis sativa L. have shown anti-obesity properties, suggesting a link between the endocannabinoid system (ECS) and obesity. However, the oral administration route has rarely been studied in this context. The aim of this study was to investigate the effect of prolonged oral administration of pure THC and CBD on obesity-related parameters and peripheral endocannabinoids. C57BL/6 male mice were fed with either a high-fat or standard diet and then received oral treatment in ramping doses, namely 10 mg/kg of THC or CBD for 5 weeks followed by 30 mg/kg for an additional 5 weeks. Mice treated with THC had attenuated weight gain and improved glucose tolerance, followed by improvement in steatosis markers and decreased hypertrophic cells in adipose epididymal tissue. Mice treated with CBD had improved glucose tolerance and increased markers of lipid metabolism in adipose and liver tissues, but in contrast to THC, CBD had no effect on weight gain and steatosis markers. CBD exclusively decreased the level of the endocannabinoid 2-arachidonoylglycerol in the liver. These data suggest that the prolonged oral consumption of THC, but not of CBD, ameliorates diet-induced obesity and metabolic parameters, possibly through a mechanism of adipose tissue adaptation.

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.

Impact of Adolescent Cannabis Use on Neurocognitive and Brain Development

Research examining associations between frequent cannabis use in adolescence and brain-behavior outcomes has increased substantially over the past 2 decades. This review attempts to synthesize the state of evidence in this area of research while acknowledging challenges in interpretation. Although there is converging evidence that ongoing, frequent cannabis use in adolescence is associated with small reductions in cognitive functioning, there is still significant debate regarding the persistence of reductions after a period of abstinence. Similarly, there is controversy regarding the replicability of structural and functional neuroimaging findings related to frequent cannabis use in adolescence. Larger studies with informative designs are needed.

Intersection between social inequality and emotion regulation on emerging adult cannabis use

Emerging adulthood (EA; ages 18-25) is characterized by socioemotional and neurodevelopmental challenges. Cannabis is a widely used substance among EAs, and hazardous use may increase risk for sustained use patterns and related health consequences. Research shows differential increases in hazardous use by objective as well as subjective measures of social inequality, with more concerning trajectories for youth with greater experiences of social inequality. Learning how to flexibly monitor and modify emotions in proactive ways (i.e., emotion regulation) is a central developmental task navigated during the EA window. Challenges to and with emotion regulation processes can contribute to the emergence of mental health symptoms during EA, including hazardous cannabis use. In this perspective, we highlight emotion dysregulation and social inequality as two critical factors that interact to either buffer against or exacerbate cannabis use during the EA period, noting critical gaps in the literature that merit additional research. We recommend novel methods and longitudinal designs to help clarify how dynamic cognition-emotion interplay predicts trajectories of negative emotional experiences and cannabis use in EA.

Lower-Risk Cannabis Use Guidelines (LRCUG) for reducing health harms from non-medical cannabis use: A comprehensive evidence and recommendations update

BACKGROUND

Cannabis use is common, especially among young people, and is associated with risks for various health harms. Some jurisdictions have recently moved to legalization/regulation pursuing public health goals. Evidence-based 'Lower Risk Cannabis Use Guidelines' (LRCUG) and recommendations were previously developed to reduce modifiable risk factors of cannabis-related adverse health outcomes; related evidence has evolved substantially since. We aimed to review new scientific evidence and to develop comprehensively up-to-date LRCUG, including their recommendations, on this evidence basis.

METHODS

Targeted searches for literature (since 2016) on main risk factors for cannabis-related adverse health outcomes modifiable by the user-individual were conducted. Topical areas were informed by previous LRCUG content and expanded upon current evidence. Searches preferentially focused on systematic reviews, supplemented by key individual studies. The review results were evidence-graded, topically organized and narratively summarized; recommendations were developed through an iterative scientific expert consensus development process.

RESULTS

A substantial body of modifiable risk factors for cannabis use-related health harms were identified with varying evidence quality. Twelve substantive recommendation clusters and three precautionary statements were developed. In general, current evidence suggests that individuals can substantially reduce their risk for adverse health outcomes if they delay the onset of cannabis use until after adolescence, avoid the use of high-potency (THC) cannabis products and high-frequency/-intensity of use, and refrain from smoking-routes for administration. While young people are particularly vulnerable to cannabis-related harms, other sub-groups (e.g., pregnant women, drivers, older adults, those with co-morbidities) are advised to exercise particular caution with use-related risks. Legal/regulated cannabis products should be used where possible.

CONCLUSIONS

Cannabis use can result in adverse health outcomes, mostly among sub-groups with higher-risk use. Reducing the risk factors identified can help to reduce health harms from use. The LRCUG offer one targeted intervention component within a comprehensive public health approach for cannabis use. They require effective audience-tailoring and dissemination, regular updating as new evidence become available, and should be evaluated for their impact.

Exploring relationships between alcohol consumption, inflammation, and brain structure in a heavy drinking sample

BACKGROUND

Chronic alcohol consumption is associated with structural brain changes and increased inflammatory signaling throughout the brain and body. Increased inflammation in the brain has been associated with structural damage. Recent studies have also shown that neurofilament light polypeptide (NfL) is released into the systemic circulation following neuronal damage. Although NfL has thus been proposed as a biomarker for neurodegenerative diseases, its connection to alcohol use disorder has not been explored. For this secondary data analysis, we proposed a conceptual model linking alcohol consumption, the pro-inflammatory cytokine IL-6, brain structure, and NfL in heavy drinking participants.

METHODS

Of the 182 individuals enrolled in this study, 81 participants had usable data on gray matter (GM) thickness and 80 had usable data on white matter (WM) diffusivity. A subset of participants had NfL (n = 78) and IL-6 (n = 117) data. An estimate of GM thickness was extracted from middle frontal brain regions using FreeSurfer. Estimated mean WM diffusivity values were extracted from Tract Based Spatial Statistics. NfL and IL-6 were measured in blood. Regression models were used to test individual linkages in the conceptual model. Based on significant regression results, we created a simplified conceptual model, which we tested using path analysis.

RESULTS

In regressions, negative relationships emerged between GM and both drinks per drinking day (DPDD) (p = 0.018) and NfL (p = 0.004). A positive relationship emerged between WM diffusivity and DPDD (p = 0.033). IL-6 was not significantly associated with alcohol use, GM or WM. The final path model demonstrated adequate fit to the data and showed significant, negative associations between DPDD and middle frontal gyrus (MFG) thickness, and between MFG thickness and NfL, but the association between DPDD and NfL was not significant.

CONCLUSIONS

This is the first study to show that heavy drinking is associated with lower GM thickness and higher WM diffusivity and that lower GM thickness is associated with higher circulating NfL. The analyses also show that the effects of drinking do not involve the pro-inflammatory cytokine IL-6.

The stoned age: Sex differences in the effects of adolescent cannabinoid exposure on prefrontal cortex structure and function in animal models

Cannabis is the most used drug during adolescence, which is a period of enhanced cortical plasticity and synaptic remodeling that supports behavioral, cognitive, and emotional maturity. In this chapter, we review preclinical studies indicating that adolescent exposure to cannabinoids has lasting effects on the morphology and synaptic organization of the prefrontal cortex and associated circuitry, which may lead to cognitive dysfunction later in life. Additionally, we reviewed sex differences in the effects of adolescent cannabinoid exposure with a focus on brain systems that support cognitive functioning. The body of evidence indicates enduring sex-specific effects in behavior and organization of corticolimbic circuitry, which appears to be influenced by species, strain, drug, route of administration, and window/pattern of drug exposure. Caution should be exercised when extrapolating these results to humans. Adopting models that more closely resemble human cannabis use will provide more translationally relevant data concerning the long-term effects of cannabis use on the adolescent brain.

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.

Cannabis Affects Cerebellar Volume and Sleep Differently in Men and Women

Background: There are known sex differences in behavioral and clinical outcomes associated with drugs of abuse, including cannabis. However, little is known about how chronic cannabis use and sex interact to affect brain structure, particularly in regions with high cannabinoid receptor expression, such as the cerebellum, amygdala, and hippocampus. Based on behavioral data suggesting that females may be particularly vulnerable to the effects of chronic cannabis use, we hypothesized lower volumes in these regions in female cannabis users. We also hypothesized poorer sleep quality among female cannabis users, given recent findings highlighting the importance of sleep for many outcomes related to cannabis use disorder. Methods: Using data from the Human Connectome Project, we examined 170 chronic cannabis users (>100 lifetime uses and/or a lifetime diagnosis of cannabis dependence) and 170 controls that we attempted to match on age, sex, BMI, race, tobacco use, and alcohol use. We performed group-by-sex ANOVAs, testing for an interaction in subcortical volumes, and in self-reported sleep quality (Pittsburgh Sleep Questionnaire Inventory). Results: After controlling for total intracranial volume and past/current tobacco usage, we found that cannabis users relative to controls had smaller cerebellum volume and poorer sleep quality, and these effects were driven by the female cannabis users (i.e., a group-by-sex interaction). Among cannabis users, there was an age of first use-by-sex interaction in sleep quality, such that females with earlier age of first cannabis use tended to have more self-reported sleep issues, whereas this trend was not present among male cannabis users. The amygdala volume was smaller in cannabis users than in non-users but the group by sex interaction was not significant. Conclusions: These data corroborate prior findings that females may be more sensitive to the neural and behavioral effects of chronic cannabis use than males. Further work is needed to determine if reduced cerebellar and amygdala volumes contribute to sleep impairments in cannabis users.

Associations of cannabis use disorder with cognition, brain structure, and brain function in African Americans

Although previous studies have highlighted associations of cannabis use with cognition and brain morphometry, critical questions remain with regard to the association between cannabis use and brain structural and functional connectivity. In a cross-sectional community sample of 205 African Americans (age 18-70) we tested for associations of cannabis use disorder (CUD, n = 57) with multi-domain cognitive measures and structural, diffusion, and resting state brain-imaging phenotypes. Post hoc model evidence was computed with Bayes factors (BF) and posterior probabilities of association (PPA) to account for multiple testing. General cognitive functioning, verbal intelligence, verbal memory, working memory, and motor speed were lower in the CUD group compared with non-users (p < .011; 1.9 < BF < 3,217). CUD was associated with altered functional connectivity in a network comprising the motor-hand region in the superior parietal gyri and the anterior insula (p < .04). These differences were not explained by alcohol, other drug use, or education. No associations with CUD were observed in cortical thickness, cortical surface area, subcortical or cerebellar volumes (0.12 < BF < 1.5), or graph-theoretical metrics of resting state connectivity (PPA < 0.01). In a large sample collected irrespective of cannabis used to minimize recruitment bias, we confirm the literature on poorer cognitive functioning in CUD, and an absence of volumetric brain differences between CUD and non-CUD. We did not find evidence for or against a disruption of structural connectivity, whereas we did find localized resting state functional dysconnectivity in CUD. There was sufficient proof, however, that organization of functional connectivity as determined via graph metrics does not differ between CUD and non-user group.

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.

Differential effects of cannabis exposure during early versus later adolescence on the expression of psychosis in homeless and precariously housed adults

Longitudinal studies of cannabis exposure during early adolescence in the general population frequently report an increased risk of subsequently developing psychotic symptoms or a psychotic illness. However, there is a dearth of knowledge about the effects of early cannabis exposure on psychosis in homeless and precariously housed adults, who represent a population afflicted with high rates of psychosis. The aim of the present study was to examine how early cannabis exposure (by age 15) compared to later first use (after age 15) affected the expression of adult psychosis in this population. Secondary measures of psychopathology, drug use, cognition and brain structure were also collected. 437 subjects were recruited from single room occupancy hotels in the urban setting of the Downtown Eastside of Vancouver, Canada. Psychiatric diagnoses were determined, and psychotic symptom severity was measured with the 5-factor PANSS. Participants completed a battery of neurocognitive tests, and brain structure was assessed using structural and diffusion tensor imaging MRI scans. Results indicated that early cannabis exposure was associated with an increased risk (OR = 1.09, p < .05) of developing substance induced psychosis, whereas later first use increased risk (OR = 2.19, p < .01) of developing schizophrenia or schizoaffective disorder. There was no group difference in neurocognitive function, although differences were observed in the lateral orbitofrontal cortex and white matter tract diffusivity. These findings indicate that early cannabis exposure in this population may increase the risk of developing drug associated psychoses, which could potentially be mediated in part through altered neurodevelopmental brain changes.

Changes in cannabis use, exposure, and health perceptions following legalization of adult recreational cannabis use in California: a prospective observational study

BACKGROUND

Most U.S. states have legalized cannabis for medical and/or recreational use. In a 6-month prospective observational study, we examined changes in adult cannabis use patterns and health perceptions following broadened legalization of cannabis use from medical to recreational purposes in California.

METHODS

Respondents were part of Stanford University's WELL for Life registry, an online adult cohort concentrated in Northern California. Surveys were administered online in the 10 days prior to state legalization of recreational use (1/1/18) and 1-month (2/1/18-2/15/18) and 6-months (7/1/2018-7/15/18) following the change in state policy. Online surveys assessed self-reported past 30-day cannabis use, exposure to others' cannabis use, and health perceptions of cannabis use. Logistic regression models and generalized estimating equations (GEE) examined associations between participant characteristics and cannabis use pre- to 1-month and 6-months post-legalization.

RESULTS

The sample (N = 429, 51% female, 55% non-Hispanic White, age mean = 56 ± 14.6) voted 58% in favor of state legalization of recreational cannabis use, with 26% opposed, and 16% abstained. Cannabis use in the past 30-days significantly increased from pre-legalization (17%) to 1-month post-legalization (21%; odds ratio (OR) = 1.28, p-value (p) = .01) and stayed elevated over pre-legalization levels at 6-months post-legalization (20%; OR = 1.28, p = .01). Exposure to others' cannabis use in the past 30 days did not change significantly over time: 41% pre-legalization, 44% 1-month post-legalization (OR = 1.18, p = .11), and 42% 6-months post-legalization (OR = 1.08, p = .61). Perceptions of health benefits of cannabis use increased from pre-legalization to 6-months post-legalization (OR = 1.19, p = .02). Younger adults, those with fewer years of education, and those reporting histories of depression were more likely to report recent cannabis use pre- and post-legalization. Other mental illness was associated with cannabis use at post-legalization only. In a multivariate GEE adjusted for sociodemographic characteristics and diagnoses, favoring legalization and the interaction of time and positive health perceptions were associated with a greater likelihood of using cannabis.

CONCLUSIONS

Legalized recreational cannabis use was associated with greater self-reported past 30-day use post-legalization, and with more-positive health perceptions of cannabis use. Future research is needed to examine longer-term perceptions and behavioral patterns following legalization of recreational cannabis use, especially among those with mental illness.

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.

Trends of the incidence of drug use disorders from 1990 to 2017: an analysis based on the Global Burden of Disease 2017 data

AIM

Drug use disorders are an important issue worldwide. Systematic attempts to estimate the global incidence of drug use disorders are rare. We aimed to determine the incidence of drug use disorders and their trends.

METHODS

We obtained the annual incident cases and age-standardised incidence rate (ASR) of drug use disorders from 1990 to 2017 using the Global Health Data Exchange query tool. The estimated annual percentage changes of the ASR were used to quantify and evaluate the trends in the incidence rate. Gaussian process regression and the Pearson's correlation coefficient were used to assess the relationship between the ASR and socio-demographic index (SDI).

RESULTS

The number of drug use disorders' cases increased by 33.5% from 1990 to 2017 globally, whereas the ASR exhibited a stable trend. The ASR was higher in men than in women. Most cases (53.1%) of drug use disorders involved opioid. A positive association (ρ=0.35, p < 0.001) was found between ASR and SDI. Teenagers aged 15-19 years had the highest incidence rate.

CONCLUSIONS

The incident cases of drug use disorders were increasing, but the incidence rate did not change significantly from 1990 to 2017. Current preventive measures and policies for drug use disorders might have little effect. The present results suggest that future strategies should focus on men, teenagers and high-risk regions in order to improve the current status of drug use disorders.

Effects of cannabis exposure in the prenatal and adolescent periods: Preclinical and clinical studies in both sexes

Cannabis is the most commonly used illicit drug among adolescents and young adults, including pregnant women. There is substantial evidence for a significant association between prenatal cannabis exposure and lower birth weight in offspring, and mixed results regarding later behavioural outcomes in the offspring. Adolescent cannabis use, especially heavy use, has been associated with altered executive function, depression, psychosis and use of other drugs later in life. Human studies have limitations due to several confounding factors and have provided scarce information about sex differences. In general, animal studies support behavioural alterations reported in humans and have revealed diverse sex differences and potential underlying mechanisms (altered mesolimbic dopaminergic and hippocampal glutamatergic systems and interference with prefrontal cortex maturation). More studies are needed that analyse sex and gender influences on cannabis-induced effects with great clinical relevance such as psychosis, cannabis use disorder and associated comorbidities, to achieve more personalized and accurate treatments.

Recent tobacco use has widespread associations with adolescent white matter microstructure

IMPORTANCE

Given the prevalence of alcohol, cannabis, and tobacco use during adolescence, it is important to explore the relative relationship of these three substances with brain structure.

OBJECTIVE

To determine associations between recent alcohol, cannabis, and tobacco use and white and gray matter in a large sample of adolescents.

DESIGN, SETTING, AND PARTICIPANTS

MRI data were collected in N = 200 adolescents ages 14-18 (M = 15.82 years; 67% male; 61% Hispanic/Latino). On average, during the past month, participants reported consuming 2.05 drinks per 1.01 drinking day, 0.64 g per 6.98 cannabis use days, and 2.49 cigarettes per 12.32 smoking days.

MAIN OUTCOMES AND MEASURES

General linear models were utilized to examine past 30-day average quantities of alcohol, cannabis, and tobacco use, age, sex, and sex by substance interactions in skeletonized white matter (fractional anisotropy and axial, radial, and mean diffusivity) and voxel-based morphometry of gray matter (volume/density).

RESULTS

Tobacco use was negatively associated with white matter integrity (radial and mean diffusivity) with peak effects in inferior and superior longitudinal fasciculi. Cannabis use was negatively associated with white matter integrity (axial diffusivity) in a small cluster in the left superior longitudinal fasciculus. No associations were observed between recent alcohol use and white or gray matter overall, but interactions showed significant negative associations between alcohol use and white matter in females.

CONCLUSIONS AND RELEVANCE

It is important to note that recent tobacco use, particularly given the popularity of e-tobacco/vaping in this age group, had widespread associations with brain structure in this sample of adolescents.

Cannabis Use in Adolescence: A Review of Neuroimaging Findings

Objective: Shifting policies and widespread acceptance of cannabis for medical and/or recreational purposes have fueled worries of increased cannabis initiation and use in adolescents. In particular, the adolescent period is thought to be associated with an increased susceptibility to the potential harms of repeated cannabis use, due to being a critical period for neuromaturational events in the brain. This review investigates the neuroimaging evidence of brain harms attributable to adolescent cannabis use. Methods: PubMed and Scopus searches were conducted for empirical articles that examined neuroimaging effects in both adolescent cannabis users and adult user studies that explored the effect of age at cannabis use onset on the brain. Results: We found 43 studies that examined brain effect (structural and functional magnetic resonance imaging) in adolescent cannabis users and 20 that examined the link between onset age of cannabis use and brain effects in adult users. Studies on adolescent cannabis users relative to nonusers mainly implicate frontal and parietal regions and associated brain activation in relation to inhibitory control, reward, and memory. However, studies in adults are more mixed, many of which did not observe an effect of onset age of cannabis use on brain imaging metrics. Conclusions: While there is some evidence of compromised frontoparietal structure and function in adolescent cannabis use, it remains unclear whether the observed effects are specifically attributable to adolescent onset of use or general cannabis use-related factors such as depressive symptoms. The relative contribution of adolescent onset of cannabis use and use chronicity will have to be more comprehensively examined in prospective, longitudinal studies with more rigorous measures of cannabis use (dosage, exposure, dependence, constituent compounds such as the relative cannabinoid levels).

Cannabis effects on brain structure, function, and cognition: considerations for medical uses of cannabis and its derivatives

Background: Cannabis is the most widely used illicit substance worldwide, and legalization for recreational and medical purposes has substantially increased its availability and use in the United States.Objectives: Decades of research have suggested that recreational cannabis use confers risk for cognitive impairment across various domains, and structural and functional differences in the brain have been linked to early and heavy cannabis use.Methods: With substantial evidence for the role of the endocannabinoid system in neural development and understanding that brain development continues into early adulthood, the rising use of cannabis in adolescents and young adults raises major concerns. Yet some formulations of cannabinoid compounds are FDA-approved for medical uses, including applications in children.Results: Potential effects on the trajectory of brain morphology and cognition, therefore, should be considered. The goal of this review is to update and consolidate relevant findings in order to inform attitudes and public policy regarding the recreational and medical use of cannabis and cannabinoid compounds.Conclusions: The findings point to considerations for age limits and guidelines for use.

A Roadmap for Integrating Neuroscience Into Addiction Treatment: A Consensus of the Neuroscience Interest Group of the International Society of Addiction Medicine

Although there is general consensus that altered brain structure and function underpins addictive disorders, clinicians working in addiction treatment rarely incorporate neuroscience-informed approaches into their practice. We recently launched the Neuroscience Interest Group within the International Society of Addiction Medicine (ISAM-NIG) to promote initiatives to bridge this gap. This article summarizes the ISAM-NIG key priorities and strategies to achieve implementation of addiction neuroscience knowledge and tools for the assessment and treatment of substance use disorders. We cover two assessment areas: cognitive assessment and neuroimaging, and two interventional areas: cognitive training/remediation and neuromodulation, where we identify key challenges and proposed solutions. We reason that incorporating cognitive assessment into clinical settings requires the identification of constructs that predict meaningful clinical outcomes. Other requirements are the development of measures that are easily-administered, reliable, and ecologically-valid. Translation of neuroimaging techniques requires the development of diagnostic and prognostic biomarkers and testing the cost-effectiveness of these biomarkers in individualized prediction algorithms for relapse prevention and treatment selection. Integration of cognitive assessments with neuroimaging can provide multilevel targets including neural, cognitive, and behavioral outcomes for neuroscience-informed interventions. Application of neuroscience-informed interventions including cognitive training/remediation and neuromodulation requires clear pathways to design treatments based on multilevel targets, additional evidence from randomized trials and subsequent clinical implementation, including evaluation of cost-effectiveness. We propose to address these challenges by promoting international collaboration between researchers and clinicians, developing harmonized protocols and data management systems, and prioritizing multi-site research that focuses on improving clinical outcomes.