Age of onset of marijuana use and executive function

Sex Differences in Response-Contingent Cannabis Vapor Administration During Adolescence Mediate Enduring Effects on Behavioral Flexibility and Prefrontal Microglia Activation in Rats

Introduction: Cannabis is the most used illicit drug in the United States. With many states passing legislation to permit its recreational use, there is concern that cannabis use among adolescents could increase dramatically in the coming years. Historically, it has been difficult to model real-world cannabis use to investigate the causal relationship between cannabis use in adolescence and behavioral and neurobiological effects in adulthood. Materials and Methods: We used a response-contingent vapor administration model to investigate long-term effects of cannabis use during adolescence on the medial prefrontal cortex (mPFC) and mPFC-dependent behaviors in male and female rats. Results: Adolescent (35- to 55-day-old) female rats had significantly higher rates of responding for vaporized Δ9-tetrahydrocannabinol (THC)-dominant cannabis extract (CANTHC) compared with adolescent males. In adulthood (70-110 days old), female, but not male, CANTHC rats also took more trials to reach criterion and made more regressive errors in an automated attentional set-shifting task compared with vehicle rats, thereby indicating sex differences in behavioral flexibility impairments. Notably, sex-treatment interactions were not observed when rats of each sex were exposed to a noncontingent CANTHC vapor dosing regimen that approximated CANTHC vapor deliveries earned by females. No differences were observed in effort-based decision making in either sex. In the mPFC, female (but not male) CANTHC rats displayed more reactive microglia with no changes in myelin basic protein expression or dendritic spine density. Conclusion: Altogether, these data reveal important sex differences in rates of responding for CANTHC vapor in adolescence that may confer enduring alterations to mPFC structure and function and suggest that there may be subtle differences in the effects of response-contingent versus noncontingent cannabis exposure that should be systematically examined in future studies.

Exploring causal mechanisms of psychosis risk

Robust epidemiological evidence of risk and protective factors for psychosis is essential to inform preventive interventions. Previous evidence syntheses have classified these risk and protective factors according to their strength of association with psychosis. In this critical review we appraise the distinct and overlapping mechanisms of 25 key environmental risk factors for psychosis, and link these to mechanistic pathways that may contribute to neurochemical alterations hypothesised to underlie psychotic symptoms. We then discuss the implications of our findings for future research, specifically considering interactions between factors, exploring universal and subgroup-specific factors, improving understanding of temporality and risk dynamics, standardising operationalisation and measurement of risk and protective factors, and developing preventive interventions targeting risk and protective factors.

Adolescent-onset cannabis use and parenting young children: an investigation of differential effectiveness of a digital parenting intervention

Introduction

There is scant empirical work on associations between current and past cannabis use and parenting skills in parents of young children. As recreational cannabis use is now legal in nearly half of states in the U.S., cannabis use is becoming more ubiquitous.

Methods

In the current study, parents of toddler and pre-school age children were randomly assigned to participate in an app-based parenting skills program that included telehealth coaching (Family Check-Up Online; FCU-O), with a focus on parenting in the context of substance use. We aimed to test associations between adolescent-onset and current cannabis use and parent mental health and parenting skills, as well as whether effects of the FCU-O on parent mental health outcomes varied as a function of past cannabis use. Participants were 356 parents of children ages 1.5-5 participating in a randomized controlled trial of the FCU-O. Parents screened into the study if they reported current or past substance misuse or current depressive symptoms. After completing a baseline assessment, parents were randomly assigned to the FCU-O or control group and completed a follow-up assessment 3 months later. Parents retrospectively reported on the age when they initially used substances, as well as their current use.

Results

After accounting for current cannabis use, adolescent-onset cannabis use was significantly associated with higher symptoms of anxiety and depression, but not with parenting skills. Adolescent-onset cannabis use was found to significantly moderate the effect of the FCU-O on parents' anxiety symptoms. Specifically, the FCU-O was particularly effective in reducing anxiety symptoms for parents with adolescent-onset regular cannabis use, after accounting for current cannabis use.

Discussion

Adolescent-onset regular cannabis use may be a risk factor for later mental health challenges in parents of children under 5. An app-based parenting intervention may be particularly helpful in reducing symptoms of anxiety for parents who used cannabis regularly as adolescents. The findings have significant implications for the prevention of multigenerational risk for substance use and mental health challenges.

Cannabis Use Characteristics Associated with Self-Reported Cognitive Function in a Nationally Representative U.S. sample

BACKGROUND

With increases in cannabis use and potency, there is a need to improve our understanding of the impact of use on cognitive function. Previous research indicates long-term cannabis use may have a negative effect on executive function. Few studies have examined persistence of it in protracted abstinence, and there is limited evidence of predictors of worse cognitive function in current and former users. In this study, we aim to evaluate the associations between cannabis use status (current, former, and never use) and self-report cognition. Further, we investigate if cannabis use characteristics predict self-report cognitive function.

METHODS

Cross-sectional cannabis use data from the National Epidemiological Survey on Alcohol and Related Conditions-III (NESARC-III), a national survey (N = 36,309) conducted in the USA between 2012 and 2013 were used alongside the Executive Function Index scales. The data were analyzed by using Ordinary Least Squares regression.

RESULTS

Current (N = 3,681, Female = 37.7%) and former users (N = 7,448, Female = 45.4%) reported poorer cognition than never users (N = 24,956, Female = 56.6%). Self-reported cognition of former users was in-between that of current and never users. Several cannabis use characteristics were associated with self-reported cognition in current and former users.

CONCLUSION

While prospective studies are required to confirm, findings suggest cannabis use is linked to worse cognition. There may be some limited recovery of cognition in former users and some cannabis use characteristics predict impairment. These findings add to our understanding of the cognitive impact of cannabis use. As worse cognitive function may impact relapse, findings have implications for personalization of cannabis use disorder treatment.

The prevalence of cannabis use disorder in attention-deficit hyperactivity disorder: A clinical epidemiological meta-analysis

Studies have shown that individuals with attention-deficit hyperactivity disorder (ADHD) pose an increased risk for developing substance use disorders. Increased cannabis product accessibility and recent legislative changes have led to increased cannabis consumption, thereby increasing the risk of cannabis use disorder (CUD). The present meta-analysis explored the lifetime and current prevalence of CUD in ADHD. A systematic review was conducted using the following databases: PubMed, PsycINFO and Web of Science. A total of 14 articles were included and used to estimate the aggregate lifetime and current prevalence of CUD in ADHD alongside risk ratios comparing increased risk of CUD in ADHD versus control samples. Mixed and random-effects models indicated that lifetime and current prevalence rates of CUD in ADHD populations were 26.9% and 19.2%, respectively (although prediction intervals ranged from 12.4% to 48.8% and 5.5%-39.1%, respectively). Analysis of the risk ratios indicated that those with ADHD were at 2.85- and 2.91-times greater risk of a lifetime or current diagnosis of CUD, respectively, than those in the general population. Our findings support the need for additional research on the prevalence of CUD in those with ADHD, as well as the inclusion of CUD screening in the treatment of ADHD.

Risk Factors for Quantity of Cannabis Use Per Day among College Students Who Violated Their University Drug Use Policy

Background

Cannabis use among college students represents a continued public health issue. The objective was to assess risk factors and reasons for cannabis use among students who violated their university's drug use policy, and whether risk factors influenced cannabis use quantity.

Methods

This cross-sectional survey study included 99 college students enrolled at a large U.S. public university. Descriptive statistics were calculated, and an ordinary least squares regression analysis was conducted.

Results

Students reported using cannabis an average of 7.4 (SD = 10.2) days in the past month, with 8% reporting daily use. On average, students consumed slightly over 0.25 (SD = 0.25) grams per day, with 40% reporting greater than one gram per day. The average age of onset of cannabis use was 16.8 (SD = 1.8) years old. The top reasons for cannabis use were to: relax or relieve tension (75.8%), feel good or get high (62.6%), and have a good time with friends (60.6%). Students perceived an average of 47% of their peers engaged in past-month cannabis use and only slight risk was associated with regular use. Students perceived their loved ones would mostly approve of a reduction in their cannabis use. Regression results indicated past-month cannabis frequency (p = .002) and being of racial/ethnic minority descent (p = .05) were positively associated with quantity of cannabis per day, while perceived risk of regular cannabis use (β = -0.21) was negatively associated.

Conclusion

Evidence-based cannabis interventions for students who violate their university's drug use policies are critically needed that aim to reduce cannabis use and mitigate its associated negative consequences.

Neurocognitive Dysfunctions in People with Concurrent Cannabis Use and Opioid Dependence: A Cross-Sectional, Controlled Study

Cannabis and opioid co-dependence is independently associated with cognitive impairments. We examined neurocognitive dysfunctions in people with concurrent opioid dependence with cannabis dependence (OD+CD) or cannabis use (OD+CU) compared to those with only opioid dependence (OD) and healthy controls (HC). We selected adult participants, any sex, who met the diagnosis of OD (N = 268), OD+CU (N = 58), and OD + CD (N = 115). We recruited 68 education-matched HC. We administeredStandard progressive matrices (SPM), Wisconsin card sorting test (WCST), Iowa gambling task (IGT), Trail making tests A and B (TMT), and verbal and visual working memory 1-, 2-backtests. 496 (97.5%) were men, and 13 (2.5%) were women. In WCST, OD and OD+CD had significantly higher non-perseverative errors than HC. OD+CD group completed significantly lesser categories than HC. In verbal working memory 2-back, HC scored significantly fewer errors than OD and OD +CD. All patient groups, OD, OD+CU, and OD+CD, scored higher commission errors than HC in visual working memory 1-back. OD and OD+CD scored higher commission and total errors than the controls. OD+CU showed lesser error score than HC in TMT B. Cannabis and opioid co-dependence contribute to cognitive impairments, especially in working memory and executive functions.

Cannabis and Cannabinoids in the Perioperative Period

Cannabis use is increasingly common, and with a growing number of jurisdictions implementing legalization frameworks, it is likely that providers will encounter more patients who use cannabis. Therefore, it is important for providers to understand the implications of cannabis use and practical considerations for the perioperative period. Cannabis affects multiple organ systems and may influence intraoperative anesthesia, as well as postoperative pain management. The effects of cannabis and key anesthetic considerations are reviewed here.

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.

Concerns Related to the Consequences of Pediatric Cannabis Use: A 360-Degree View

Cannabis, a plant known for its recreational use, has gained global attention due to its widespread use and addiction potential. Derived from the Cannabis sativa plant, it contains a rich array of phytochemicals concentrated in resin-rich trichomes. The main cannabinoids, delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), interact with CB1 and CB2 receptors, influencing various physiological processes. Particularly concerning is its prevalence among adolescents, often driven by the need for social connection and anxiety alleviation. This paper provides a comprehensive overview of cannabis use, its effects, and potential health risks, especially in adolescent consumption. It covers short-term and long-term effects on different body systems and mental health and highlights the need for informed decision making and public health initiatives, particularly regarding adolescent cannabis use.

The long-term effects of adolescent Δ9-tetrahydrocannabinol on brain structure and function assessed through neuroimaging techniques in male and female rats

Several studies performed on human subjects have examined the effects of adolescent cannabis consumption on brain structure or function using brain imaging techniques. However, the evidence from these studies is usually heterogenous and affected by several confounding variables. Animal models of adolescent cannabinoid exposure may help to overcome these difficulties. In this exploratory study, we aim to increase our understanding of the protracted effects of adolescent Δ9-tetrahydrocannabinol (THC) in rats of both sexes using magnetic resonance (MR) to obtain volumetric data, assess grey and white matter microstructure with diffusion tensor imaging (DTI) and measure brain metabolites with 1H-MR spectroscopy (MRS); in addition, we studied brain function using positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-d-glucose as the tracer. THC-exposed rats exhibited volumetric and microstructural alterations in the striatum, globus pallidus, lateral ventricles, thalamus, and septal nuclei in a sex-specific manner. THC administration also reduced fractional anisotropy in several white matter tracts, prominently in rostral sections, while in vivo MRS identified lower levels of cortical choline compounds. THC-treated males had increased metabolism in the cerebellum and olfactory bulb and decreased metabolism in the cingulate cortex. By contrast, THC-treated females showed hypermetabolism in a cluster of voxels comprising the entorhinal piriform cortices and in the cingulate cortex. These results indicate that mild THC exposure during adolescence leaves a lingering mark on brain structure and function in a sex-dependant manner. Some of the changes found here resemble those observed in human studies and highlight the importance of studying sex-specific effects in cannabinoid research.

Does tobacco dependence worsen cannabis withdrawal in people with and without schizophrenia-spectrum disorders?

BACKGROUND AND OBJECTIVES

Rates of cannabis use disorder (CUD) are higher in people with schizophrenia than in the general population. Irrespective of psychiatric diagnosis, tobacco co-use is prevalent in those with CUD and leads to poor cannabis cessation outcomes. The cannabis withdrawal syndrome is well-established and increases cannabis relapse risk. We investigated whether cannabis withdrawal severity differed as a function of high versus no/low tobacco dependence and psychiatric diagnosis in individuals with CUD.

METHOD

Men with CUD (N = 55) were parsed into four groups according to schizophrenia diagnosis and tobacco dependence severity using the Fagerstrom Test for Nicotine Dependence (FTND): men with schizophrenia with high tobacco dependence (SCT+, n = 13; FTND ≥ 5) and no/low tobacco dependence (SCT-, n = 22; FTND ≤ 4), and nonpsychiatric controls with high (CCT+, n = 7; FTND ≥ 5) and no/low (CCT-, n = 13; FTND ≤ 4) tobacco dependence. Participants completed the Marijuana Withdrawal Checklist following 12-h of cannabis abstinence.

RESULTS

There was a significant main effect of tobacco dependence on cannabis withdrawal severity (p < .001). Individuals with high tobacco dependence had significantly greater cannabis withdrawal severity (M = 13.85 [6.8]) compared to individuals with no/low tobacco dependence (M = 6.49, [4.9]). Psychiatric diagnosis and the interaction effects were not significant. Lastly, cannabis withdrawal severity positively correlated with FTND (r = .41, p = .002).

CONCLUSION AND SCIENTIFIC SIGNIFICANCE

Among individuals with CUD and high tobacco dependence, cannabis withdrawal severity was elevated twofold, irrespective of diagnosis, relative to individuals with CUD and no/low tobacco dependence. Findings from this study emphasize the importance of addressing tobacco co-use when treating CUD.

Impaired cognitive control moderates the relation between the attribution of incentive salience and severity of consumption in patients with methamphetamine dependence

BACKGROUND

Cognitive control and the attribution of incentive salience are two key neuropsychological processes proposed to explain substance use disorder (SUD). However, little is known about how they interact to influence the severity of drug use in people with SUD.

OBJECTIVE

To determine if cognitive control exerts a moderating effect on the relation between the attribution of salience to drug/reward-related cues and the severity of drug use in SUD cases.

METHOD

Sixty-nine SUD cases with methamphetamine as the main drug of consumption were selected and evaluated. Participants performed the Stroop, Go/No-Go, and Flanker tasks to identify a latent cognitive control factor, and the Effort-Expenditure for Reward task, as well as answering the Methamphetamine Incentive Salience Questionnaire to measure the attribution of incentive salience. Severity of drug use was determined by the KMSK scale and an exploratory clinical interview.

RESULTS

As expected, higher incentive salience attribution predicted greater severity of methamphetamine use. Unexpectedly, however, we found a moderating effect of impaired cognitive control on the relations between higher incentive salience scores and higher monthly drug use, and between younger age at onset of systematic drug use and higher incentive salience scores.

CONCLUSION

Results show the moderating role of cognitive control on the relation between incentive salience attribution and severity of drug use in SUD cases, and help explain the chronic, relapsing nature of addiction, knowledge necessary to develop more precise prevention and treatment strategies.

Ratings of executive function as a risk factor for adolescents' frequent cannabis use: A prospective longitudinal study

OBJECTIVE

We examined the extent to which behavioral ratings of children's executive function (EF) in early adolescence predicted adolescents' cannabis use, and whether associations were independent of parents' cannabis and alcohol use and adolescents' alcohol use.

METHOD

Participants were 198 offspring (44% boys) of 127 mothers and 106 fathers. Parents and teachers completed the Behavior Rating Inventory of Executive Function (BRIEF) at ages 11-14 years. Youth were interviewed repeatedly from ages 14 to 20 years regarding frequency of cannabis and alcohol use. Two-level models regressed dichotomous cannabis outcomes (annual, weekly, or daily use) on age at the within-person level and the random intercept of cannabis use on EF, parent substance use, and covariates (age 7 IQ indicators, child gender, parent education, and mean of ages assessed) at the between-person level.

RESULTS

Poorer child EF predicted significantly (p < .05) higher likelihood of weekly (b[SE] = .64[.24]) and daily (b[SE] = .65[.25]), but not annual (b[SE] = .38[.22]), cannabis use. Parent cannabis use (b[SE] = .53[.25] to .81[.39], p < .05) independently predicted all three outcomes, and effects were distinct from those explained by parent alcohol use (b[SE] = .66[.29] to .81[.35], p < .05). EF remained a significant predictor of weekly and daily cannabis use after adjusting for parental alcohol and cannabis use, and adolescents' alcohol use.

CONCLUSIONS

Children exhibiting poorer EF were more likely to use cannabis weekly and daily in later adolescence. Whereas literature suggests poorer EF may be a consequence of cannabis use, these findings suggest EF should be considered prior to cannabis use initiation. EF during childhood may be a fruitful prevention target. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Prospective, longitudinal study to isolate the impacts of marijuana use on neurocognitive functioning in adolescents

Introduction

Policies to legalize possession and use of marijuana have been increasingly supported across the United States. Although there are restrictions on use in minors, many substance abuse scientists anticipate that these policy changes may alter use patterns among adolescents due to its wider availability and a softening of beliefs about its potentially harmful consequences. Despite the possibility that these policies may increase the prevalence of use among adolescents, the effects of marijuana on neurodevelopment remain unclear, clouding arguments in favor of or opposition to these policies.

Methods

The present prospective, longitudinal study was designed to isolate the neurodevelopmental consequences of marijuana use from its precursors during adolescence-a period of heightened vulnerability for both substance use and disrupted development due to environmental insults. Early adolescents who were substance-naïve at baseline (N = 529, aged 10-12) were recruited and tracked into adolescence when a subgroup initiated marijuana use during one of three subsequent waves of data collection, approximately 18 months apart.

Results

Results suggest that marijuana use may be specifically related to a decline in verbal learning ability in the short term and in emotion recognition, attention, and inhibition in the longer-term.

Discussion

These preliminary findings suggest that marijuana use has potential to adversely impact vulnerable neurodevelopmental processes during adolescence. Intensive additional investigation is recommended given that state-level policies regulating marijuana use and possession are rapidly shifting in the absence of good scientific information.

CannaCount: an improved metric for quantifying estimates of maximum possible cannabinoid exposure

Increasing numbers of individuals have access to cannabinoid-based products containing various amounts of delta-9-tetrahydrocannabinol (THC), cannabidiol (CBD), and other cannabinoids. Exposure to specific cannabinoids likely influences outcomes; however, current methods for quantifying cannabis exposure do not account for the cannabinoid concentrations of the products used. We developed CannaCount, an examiner-driven metric that quantifies estimated maximum possible cannabinoid exposure by accounting for variables related to cannabinoid concentration, duration, frequency, and quantity of use. To demonstrate feasibility and applicability, CannaCount was used to quantify estimated maximum THC and CBD exposure in 60 medical cannabis patients enrolled in a two-year, longitudinal, observational study. Medical cannabis patients reported using a variety of product types and routes of administration. Calculating estimated exposure to THC and CBD was possible for the majority of study visits, and the ability to generate estimated cannabinoid exposure improved over time, likely a function of improved product labeling, laboratory testing, and more informed consumers. CannaCount is the first metric to provide estimated maximum possible exposure to individual cannabinoids based on actual cannabinoid concentrations. This metric will ultimately facilitate cross-study comparisons and can provide researchers and clinicians with detailed information regarding exposure to specific cannabinoids, which will likely have significant clinical impact.

Chronic cannabis use alters dACC-striatal glutamatergic balance

Prefrontal and striatal glutamate plays an important role in modulating striatal dopamine levels and an imbalance in regional glutamate has been identified in several psychiatric conditions. We hypothesized that this imbalance also exists in cannabis use disorder (CUD). We recently quantified the difference in glutamate of dorsal anterior cingulate (dACC) and striatum regions in the frontostriatal pathway using proton MRS at baseline and on verified abstinent days 7 and 21 in chronic users of cannabis (n = 20) in comparison with age- and sex- matched non-using controls (n = 10). In addition, the Barratt Impulsiveness Scale-11 (BIS) was collected as a measure of inhibitory impulse control of the participants. We found that the difference in glutamate concentrations between the dACC and striatum (ΔdACC-strGlu) of the controls was significantly higher than that of cannabis users across the study timeline (F(1,28) = 18.32, p < 0.0005). The group difference was not affected by age, sex, or alcohol/cigarette consumption. On abstinent day 7, ΔdACC-strGlu was significantly correlated with the corresponding ΔdACC-strGABA among the users (r = 0.837, p < 0.00001). On day 21, ΔdACC-strGlu was negatively associated with monthly cannabis use days (Spearman's rho = -0.444, p = 0.05). Self-reported BIS and its subscales were significantly altered among the users compared to the controls across the study timeline (total F(1,28) = 7.0, p = 0.013; non-planning F(1,28) = 16.1, p < 0.0005; motor F(1,28) = 5.9, p = 0.022; cognitive F(1,28) = 6.1, p = 0.019). These data provide preliminary evidence that chronic cannabis use may lead to a dACC-striatal glutamate imbalance in conjunction with poor impulse control.

Measuring white matter microstructure in 1,457 cannabis users and 1,441 controls: A systematic review of diffusion-weighted MRI studies

INTRODUCTION

Cannabis is the most widely used regulated substance by youth and adults. Cannabis use has been associated with psychosocial problems, which have been partly ascribed to neurobiological changes. Emerging evidence to date from diffusion-MRI studies shows that cannabis users compared to controls show poorer integrity of white matter fibre tracts, which structurally connect distinct brain regions to facilitate neural communication. However, the most recent evidence from diffusion-MRI studies thus far has yet to be integrated. Therefore, it is unclear if white matter differences in cannabis users are evident consistently in selected locations, in specific diffusion-MRI metrics, and whether these differences in metrics are associated with cannabis exposure levels.

METHODS

We systematically reviewed the results from diffusion-MRI imaging studies that compared white matter differences between cannabis users and controls. We also examined the associations between cannabis exposure and other behavioral variables due to changes in white matter. Our review was pre-registered in PROSPERO (ID: 258250; https://www.crd.york.ac.uk/prospero/).

RESULTS

We identified 30 diffusion-MRI studies including 1,457 cannabis users and 1,441 controls aged 16-to-45 years. All but 6 studies reported group differences in white matter integrity. The most consistent differences between cannabis users and controls were lower fractional anisotropy within the arcuate/superior longitudinal fasciculus (7 studies), and lower fractional anisotropy of the corpus callosum (6 studies) as well as higher mean diffusivity and trace (4 studies). Differences in fractional anisotropy were associated with cannabis use onset (4 studies), especially in the corpus callosum (3 studies).

DISCUSSION

The mechanisms underscoring white matter differences are unclear, and they may include effects of cannabis use onset during youth, neurotoxic effects or neuro adaptations from regular exposure to tetrahydrocannabinol (THC), which exerts its effects by binding to brain receptors, or a neurobiological vulnerability predating the onset of cannabis use. Future multimodal neuroimaging studies, including recently developed advanced diffusion-MRI metrics, can be used to track cannabis users over time and to define with precision when and which region of the brain the white matter changes commence in youth cannabis users, and whether cessation of use recovers white matter differences.

SYSTEMATIC REVIEW REGISTRATION

www.crd.york.ac.uk/prospero/, identifier: 258250.

Sex differences in adolescent cannabis vapor self-administration mediate enduring effects on behavioral flexibility and prefrontal microglia activation in rats

Cannabis is the most used illicit drug in the United States. With many states passing legislation to permit its recreational use, there is concern that cannabis use among adolescents could increase dramatically in the coming years. Historically, it has been difficult to model real-world cannabis use to investigate the causal relationship between cannabis use in adolescence and behavioral and neurobiological effects in adulthood. To this end, we used a novel volitional vapor administration model to investigate long-term effects of cannabis use during adolescence on the medial prefrontal cortex (mPFC) and mPFC-dependent behaviors in male and female rats. Adolescent (35-55 day old) female rats had significantly higher rates of responding for vaporized Δ9-tetrahydrocannabinol (THC)-dominant cannabis extract (CANTHC) compared to adolescent males. In adulthood (70-110 day old), female, but not male, CANTHC rats also took more trials to reach criterion and made more regressive errors in an automated attentional set-shifting task compared to vehicle rats. Similar set-shifting deficits were observed in males when they were exposed to a non-contingent CANTHC vapor dosing regimen that approximated CANTHC self-administration rates in females. No differences were observed in effort-based decision making in either sex. In the mPFC, female (but not male) CANTHC rats displayed more reactive microglia with no significant changes in myelin basic protein expression or dendritic spine density. Together, these data reveal important sex differences in rates of cannabis vapor self-administration in adolescence that confer enduring alterations to mPFC structure and function. Importantly, female-specific deficits in behavioral flexibility appear to be driven by elevated rates of CANTHC self-administration as opposed to a sex difference in the effects of CANTHC vapor per se.

Effect of Cannabis on Memory Consolidation, Learning and Retrieval and Its Current Legal Status in India: A Review

Cannabis is one of the oldest crops grown, traditionally held religious attachments in various cultures for its medicinal use much before its introduction to Western medicine. Multiple preclinical and clinical investigations have explored the beneficial effects of cannabis in various neurocognitive and neurodegenerative diseases affecting the cognitive domains. Tetrahydrocannabinol (THC), the major psychoactive component, is responsible for cognition-related deficits, while cannabidiol (CBD), a non-psychoactive phytocannabinoid, has been shown to elicit neuroprotective activity. In the present integrative review, the authors focus on the effects of cannabis on the different cognitive domains, including learning, consolidation, and retrieval. The present study is the first attempt in which significant focus has been imparted on all three aspects of cognition, thus linking to its usage. Furthermore, the investigators have also depicted the current legal position of cannabis in India and the requirement for reforms.

The Relationship Between Cannabis, Cognition, and Schizophrenia: It's Complicated

The consequences of cannabis use, especially in the context of schizophrenia, have gained increased importance with the legalization of cannabis in North America and across the globe. Cannabis use has multifaceted impacts on cognition in schizophrenia patients and healthy subjects. Healthy subjects, particularly those who initiated cannabis use at earlier ages and used high-potency cannabis for longer durations, exhibited poorer cognition mainly in working memory and attention. Cannabis use in schizophrenia has been associated with symptom exacerbation, longer and more frequent psychotic episodes, and poorer treatment outcomes. However, cannabis-using patients have better overall cognitive performance compared to patients who were not cannabis users. Interestingly, these effects were only apparent in lifetime cannabis users, but not in current (or within last 6 months) users. Moreover, higher frequency and earlier age of cannabis use initiation (i.e., before 17 years of age) were associated with better cognitive performance, although they had an earlier illness onset. Three possible hypotheses seem to come forward to explain this paradox. First, some components of cannabis may have antipsychotic or cognitive-enhancing properties. Secondly, chronic cannabis use may alter endocannabinoid signaling in the brain which could be a protective factor for developing psychosis or cognitive impairments. A third explanation could be their representation of a phenotypically distinct patient group with more intact cognitive functioning and less neurodevelopmental pathology. Multiple factors need to be considered to understand the complex relationship between cannabis, cognitive function, and schizophrenia. In short, age at initiation, duration and rate of cannabis use, abstinence duration, co-use of substances and alcohol, prescribed medications, relative cannabinoid composition and potency of cannabis, presence of genetic and environmental vulnerability factors are prominent contributors to the variability in outcomes. Animal studies support the disruptive effects of Δ9-tetrahydrocannabinol (THC) administration during adolescence on attention and memory performance. They provide insights about interaction of cannabinoid receptors with other neurotransmitter systems, such as GABA and glutamate, and other regulatory molecules, such as PSD95 and synaptophysin. Cannabidiol (CBD), on the other hand, can improve cognitive deficits seen in neurodevelopmental and chemically-induced animal models of schizophrenia. Future studies focusing on bridging the translational gaps between human and animal studies, through the use of translationally relevant methods of exposure (e.g., vaping), consistent behavioral assessments, and congruent circuit interrogations (e.g., imaging) will help to further clarify this complex picture.

Enhancing axonal myelination in seniors: A review exploring the potential impact cannabis has on myelination in the aged brain

Consumption of cannabis is on the rise as public opinion trends toward acceptance and its consequent legalization. Specifically, the senior population is one of the demographics increasing their use of cannabis the fastest, but research aimed at understanding cannabis' impact on the aged brain is still scarce. Aging is characterized by many brain changes that slowly alter cognitive ability. One process that is greatly impacted during aging is axonal myelination. The slow degradation and loss of myelin (i.e., demyelination) in the brain with age has been shown to associate with cognitive decline and, furthermore, is a common characteristic of numerous neurological diseases experienced in aging. It is currently not known what causes this age-dependent degradation, but it is likely due to numerous confounding factors (i.e., heightened inflammation, reduced blood flow, cellular senescence) that impact the many cells responsible for maintaining overall homeostasis and myelin integrity. Importantly, animal studies using non-human primates and rodents have also revealed demyelination with age, providing a reliable model for researchers to try and understand the cellular mechanisms at play. In rodents, cannabis was recently shown to modulate the myelination process. Furthermore, studies looking at the direct modulatory impact cannabis has on microglia, astrocytes and oligodendrocyte lineage cells hint at potential mechanisms to prevent some of the more damaging activities performed by these cells that contribute to demyelination in aging. However, research focusing on how cannabis impacts myelination in the aged brain is lacking. Therefore, this review will explore the evidence thus far accumulated to show how cannabis impacts myelination and will extrapolate what this knowledge may mean for the aged brain.

Psychological reactance and adolescent cannabis use: The role of parental warmth and monitoring

Psychological reactance (PR) is a psychological state or trait typified by resistant responses to threats to behavioral freedom. PR has been linked with negative health behaviors, including risky substance use; however, factors that may foster approaches to mitigate the impact of PR on these behaviors, as well as rejection of other health promotion communications is less understood. The current studies examined relations between parental warmth and monitoring with trait PR and responses to preventive cannabis communications and usage intentions. Two in-school surveys were administered to two difference samples of middle school students (Study 1, N = 1,416; Study 2, N = 1,118). Path analytic models tested multivariable linkages among relevant parenting variables, PR, and outcomes associated with cannabis use. Follow-up regression analyses explored significant interaction effects. In Study 1 (p <0.001) and Study 2 (p <0.01), parental warmth moderated the relation between monitoring and trait PR: High monitoring was a protective factor only when combined with high warmth. In turn, PR mediated the relationships between parenting practices and cannabis intentions in both studies (p <0.001). In Study 2, PR also was linked with resistance to persuasion via more unfavorable reactions to anti-cannabis appeals (p <0.001). Findings indicated that low parental warmth combined with high parental monitoring was associated with high trait reactance in adolescents, which predisposed them to stronger resistance to preventive communications. Interventions might focus on counseling parents about the likely outcomes of parenting style, and ways to implement beneficial approaches.

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.

Cyberbullying involvement, parental support, and cannabis use among adolescents

BACKGROUND

Cyberbullying victimization has been associated with cannabis use among adolescents. However, it is unclear if this relationship also holds for cyberbullying perpetrators.

OBJECTIVE

This cross-sectional study examined the association between cyberbullying involvement and cannabis use among adolescents and tested if parental support was associated with cyberbullying involvement and cannabis use.

PARTICIPANTS AND SETTING

Data from 7229 students aged 11-20 years were obtained from the 2019 Ontario Student Drug Use and Health Survey, a province-wide survey of middle and high school students across Ontario, Canada.

METHODS

Participants self-reported their cannabis use frequency, their involvement in cyberbullying, and their perception of parental support. Cyberbullying involvement was operationalized as an action taking place at least two times. Multivariable logistic regression models were adjusted for age, sex, ethnoracial background, and subjective socioeconomic status.

RESULTS

Overall, 8.6 % of students were cyberbullying victims only, 2 % were cyberbullying perpetrators only, and 2.8 % were both cyberbullying victims and perpetrators. Results showed that experience of cyberbullying victimization only (OR: 2.17; 95 % CI: 1.64-2.88), perpetration only (OR: 2.64; 95 % CI: 1.51-4.63), or both (OR: 3.34; 95 % CI: 2.12-5.28) was associated with greater odds of cannabis use. Results further indicated that higher parental support was associated with lower odds of cannabis use in a dose-response fashion. Higher parental support was also associated with a lower risk of cyberbullying involvement.

CONCLUSIONS

These findings suggest that involvement in cyberbullying in any role is associated with greater cannabis use among adolescents and that parental support is associated with less cannabis use and cyberbullying involvement.

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.

Cannabis Use and Parenting Practices among Young People: The Impact of Parenting Styles, Parental Cannabis-Specific Rules, and Parental Cannabis Use

Cannabis is the most commonly used illicit drug. Its use typically starts in adolescence, and parents play a key role in young people’s cannabis use. Our study aimed to examine and compare the effects of parenting styles, parental cannabis-specific rules, and parental cannabis use on young people’s cannabis use. The research sample consisted of 839 students from various secondary education programs in Slovenia, aged 14 to 21. Associations between the young people’s lifetime cannabis use and their experience of parenting practices were assessed using logistic regression, with demographic, socioeconomic, educational, health, and risk behaviors controlled in a multivariate model. Maternal authoritative parenting (in comparison with permissive parenting), strict maternal, cannabis-specific rules, and parental cannabis non-use statistically significantly reduced the likelihood of young people’s cannabis use. Its strongest predictor was parental cannabis use, followed by the mother’s specific cannabis-use rules and maternal parenting style. The findings of our study can contribute to the development of public health policies to more effectively prevent cannabis use among adolescents and emerging adults, including by designing prevention programs aimed at strengthening parents’ general and cannabis-specific practices and competences.

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.

Information Scanning Impacts Nonmedical Drug Use Among College Students: A Longitudinal Study of Scanning Effects

Health information that is acquired through information scanning has been shown to play an important role in shaping individual beliefs and health behavior. This study examines the direct and indirect effects of the breadth of scanning from media and interpersonal sources about two risk behaviors (nonmedical use of amphetamines and marijuana) on subsequent drug use behavior through changes to perceived norms. We test effects of scanning using a longitudinal online survey design with data collected at six-month intervals over three time points among 800 Israeli undergraduate students in their freshman year. Of the 800 respondents who participated in the first wave, 62.4% completed the second wave (N = 499), among which 347 (69.5%) completed a follow-up 6 months later. Results of cross-lagged structural equation models find that scanning information about amphetamines from interpersonal sources at 6 months predicted an increased likelihood of nonmedical use of amphetamines at 12-months. In addition, young adults who scanned information about marijuana from media sources at 6 months reported greater nonmedical marijuana use at 12 months. Breadth of scanning about marijuana from media sources mediated the relationship between perceived norms and marijuana use at 12 months. Results also showed indirect effects of scanning at baseline on nonmedical drug use at 12 months through scanning from the same source at 6 months. These findings contribute to our understanding of the role of information scanning and perceived norms in shaping substance use behaviors, and suggest that scanning may serve as a potential early indicator of risk.

Medical marijuana for inflammatory bowel disease: the highs and lows

Increased interest in cannabis as a potential treatment and/or adjuvant therapy for inflammatory bowel disease (IBD) has been driven by patients with refractory disease seeking relief as well those who desire alternatives to conventional therapies. Available data have shown a potential role of cannabis as a supportive medication, particularly in pain reduction; however, it remains unknown whether cannabis has any impact on the underlying inflammatory process of IBD. The purpose of this review article is to summarize the available literature concerning the use of cannabis for the treatment of IBD and highlight potential areas for future study.

Adolescent cannabis experimentation and unemployment in young to mid-adulthood: Results from the French TEMPO Cohort study

BACKGROUND

France accounts for one of the highest levels of recreational cannabis use, with almost 40% of youth aged 17 reporting having experimented with cannabis. We investigated the impact of early cannabis experimentation (defined as first-time use ≤ 16 years) on future probability of unemployment in young to mid-adulthood using a longitudinal, community sample over the span of 9 years.

METHODS

Data were obtained from the French TEMPO Cohort study, set up in 2009 among young adults aged 22-25 years old. Participants who reported information on age of cannabis experimentation and employment status in at least one study wave (2009, 2011, 2015 and 2018) were included in the statistical analyses (N = 1487, 61.2% female).

RESULTS

In A-IPW-adjusted analyses, early cannabis experimenters (≤ 16 years) had 1.71 (95% CI: 1.46-2.02) times higher odds of experiencing unemployment compared to late cannabis experimenters (> 16 years) and 2.40 (95% CI: 2.00 - 2.88) times higher odds of experiencing unemployment compared to non-experimenters. Late cannabis experimenters experienced 1.39 (95% CI: 1.17-1.68) times higher odds of being unemployed compared to non-experimenters, and early cannabis experimenters experienced 3.84 (95%CI: 2.73-5.42) times higher odds of experiencing long-term unemployment (defined as unemployed at least twice) compared to non-experimenters.

CONCLUSIONS

Participants who ever used cannabis, especially at or before the age of 16, had higher odds of experiencing unemployment, even when accounting for many psychological, academic and family characteristics which preceded cannabis initiation.

Effects of cannabinoid exposure on short-term memory and medial orbitofrontal cortex function and chemistry in adolescent female rhesus macaques

Aim

There is increasing concern that cannabinoid exposure during adolescence may disturb brain maturation and produce long-term cognitive deficits. However, studies in human subjects have provided limited evidence for such causality. The present study utilized behavioral and neuroimaging endpoints in female non-human primates to examine the effects of acute and chronic exposure during adolescence to the cannabinoid receptor full agonist, AM2389, on cognitive processing and brain function and chemistry.

Materials and methods

Adolescent female rhesus macaques were trained on a titrating-delay matching-to-sample (TDMTS) touchscreen task that assays working memory. TDMTS performance was assessed before and during chronic exposure to AM2389, following antagonist (rimonabant) administration, and after discontinuation of the chronic regimen. Resting-state fMRI connectivity and magnetic resonance spectroscopy data were acquired prior to drug treatment, during chronic exposure, and following its discontinuation. Voxels were placed in the medial orbitofrontal cortex (mOFC), a region involved in memory processing that undergoes maturation during adolescence.

Results

TDMTS performance was dose-dependently disrupted by acute AM2389; however, chronic treatment resulted in tolerance to these effects. TDMTS performance also was disrupted by discontinuation of the chronic regimen but surprisingly, not by rimonabant administration during chronic AM2389 treatment. mOFC N-acetylaspartate/creatine ratio decreased after acute and chronic administration but returned to baseline values following discontinuation of chronic treatment. Finally, intra-network functional connectivity (mOFC) increased during the chronic regimen and returned to baseline values following its discontinuation.

Conclusion

Neural effects of a cannabinergic drug may persist during chronic exposure, notwithstanding the development of tolerance to behavioral effects. However, such effects dissipate upon discontinuation, reflecting the restorative capacity of affected brain processes.

Theta and Alpha Oscillatory Activity During Working Memory Maintenance in Long-Term Cannabis Users: The Importance of the Polydrug Use Context

Background: Impairments in various subdomains of memory have been associated with chronic cannabis use, but less is known about their neural underpinnings, especially in the domain of the brain's oscillatory activity. Aims: To investigate neural oscillatory activity supporting working memory (WM) in regular cannabis users and non-using controls. We focused our analyses on frontal midline theta and posterior alpha asymmetry as oscillatory fingerprints for the WM's maintenance process. Methods: 30 non-using controls (CG) and 57 regular cannabis users-27 exclusive cannabis users (CU) and 30 polydrug cannabis users (PU) completed a Sternberg modified WM task with a concurrent electroencephalography recording. Theta, alpha and beta frequency bands were examined during WM maintenance. Results: When compared to non-using controls, the PU group displayed increased frontal midline theta (FMT) power during WM maintenance, which was positively correlated with RT. The posterior alpha asymmetry during the maintenance phase, on the other hand, was negatively correlated with RT in the CU group. WM performance did not differ between groups. Conclusions: Both groups of cannabis users (CU and PU), when compared to the control group, displayed differences in oscillatory activity during WM maintenance, unique for each group (in CU posterior alpha and in PU FMT correlated with performance). We interpret those differences as a reflection of compensatory strategies, as there were no differences between groups in task performance. Understanding the psychophysiological processes in regular cannabis users may provide insight on how chronic use may affect neural networks underlying cognitive processes, however, a polydrug use context (i.e., combining cannabis with other illegal substances) seems to be an important factor.

Neuropsychological performance in young adults with cannabis use disorder

BACKGROUND AND AIMS

Cannabis is a commonly used recreational drug in young adults. The worldwide prevalence in 18- to 25-year-olds is approximately 35%. Significant differences in cognitive performance have been reported previously for groups of cannabis users. However, the groups are often heterogeneous in terms of cannabis use. Here, we study daily cannabis users with a confirmed diagnosis of cannabis use disorder (CUD) to examine cognitive performance on measures of memory, executive function and risky decision-making.

METHODS

Forty young adult daily cannabis users with diagnosed CUD and 20 healthy controls matched for sex and premorbid intelligence quotient (IQ) were included. The neuropsychological battery implemented was designed to measure multiple modes of memory (visual, episodic and working memory), risky decision-making and other domains of executive function using subtests from the Cambridge Neuropsychological Test Automated Battery (CANTAB).

RESULTS

Our results showed that young adult daily cannabis users with CUD perform significantly poorer on tasks of visual and episodic memory compared with healthy controls. In addition, executive functioning was associated with the age of onset.

CONCLUSIONS

Further research is required to determine whether worse performance in cognition results in cannabis use or is a consequence of cannabis use. Chronic heavy cannabis use during a critical period of brain development may have a particularly negative impact on cognition. Research into the persistence of cognitive differences and how they relate to functional outcomes such as academic/career performance is required.

GEOGRAPHICAL ACCESS TO RECREATIONAL MARIJUANA

We investigate whether adult marijuana use in Washington responds to increased local access as measured by drive time to the nearest legal marijuana retailer as well as measures of retail density. Using survey data from the Behavioral Risk Factor Surveillance System, we find that as retailers open closer to where they live, more individuals use marijuana and more frequently. These effects are concentrated among young adults (ages 18-26), women, and rural residents. Controlling for distance to the nearest retailer, we find that whether retail density affects marijuana use depends on how it is measured.

Trends in substance use and prevention education involvement among U.S. adolescents receiving public assistance: new evidence

PURPOSE

The present study aimed to examine the substance use prevention education involvement in different social settings among adolescents receiving public assistance-cash or food voucher-for low household income (heretofore, "PA program enrollees") and preventive effects of each prevention educational setting on current substance use.

METHODS

Using data from a nationally-representative sample of PA program enrollees from the 2002-2017 National Survey on Drug Use and Health, we estimated the prevalence of substance use prevention education involvement in home, school, and neighborhood settings and the associations between involvement in each educational setting and current alcohol/illicit drug use.

RESULTS

Compared to nonenrollees, PA program enrollees reported significantly lower rates of involvement in all prevention education settings, including parent-child conversations (54.6% vs. 60.1%) and neighborhood prevention resources (71.3% vs. 79.3%). All educational setting were associated with lower odds of current substance use, with the largest effects found for parent-child conversations (AOR = 0.821 [P < .001] for alcohol use; AOR = 0.817 [P < .001] for illicit drug use).

CONCLUSIONS

To reduce the elevated risk of illicit drug use among PA program enrollees, special attention needs to be paid to promote parent-child conversation about substance use and increase access to prevention education in regular classes and preventive messages outside schools.

The Effects of Cannabis Use on Cognitive Function in Healthy Aging: A Systematic Scoping Review

BACKGROUND

Older adults (≥50 years) represent the fastest-growing population of people who use cannabis, potentially due to the increasing promotion of cannabis as medicine by dispensaries and cannabis websites. Given healthy aging and cannabis use are both associated with cognitive decline, it is important to establish the effects of cannabis on cognition in healthy aging.

OBJECTIVE

This systematic scoping review used preferred reporting items for systematic reviews and meta-analyses guidelines to critically examine the extent of literature on this topic and highlight areas for future research.

METHOD

A search of six databases (PubMed, EMBASE, PsycINFO, Web of Science, Family and Society Studies Worldwide, and CINAHL) for articles published by September 2019, yielded 1,014 unique results.

RESULTS

Six articles reported findings for older populations (three human and three rodent studies), highlighting the paucity of research in this area. Human studies revealed largely null results, likely due to several methodological limitations. Better-controlled rodent studies indicate that the relationship between ∆9-tetrahydrocannabinol (THC) and cognitive function in healthy aging depends on age and level of THC exposure. Extremely low doses of THC improved cognition in very old rodents. Somewhat higher chronic doses improved cognition in moderately aged rodents. No studies examined the effects of cannabidiol (CBD) or high-CBD cannabis on cognition.

CONCLUSIONS

This systematic scoping review provides crucial, timely direction for future research on this emerging issue. Future research that combines neuroimaging and cognitive assessment would serve to advance understanding of the effects of age and quantity of THC and CBD on cognition in healthy aging.

Cannabis Use, Age of Initiation, and Neurocognitive Performance: Findings from a Large Sample of Heavy Drinking Emerging Adults

OBJECTIVE

To evaluate the associations between cannabis use and neurocognitive functioning, including self-reported attention deficit hyperactivity disorder (ADHD) symptoms, in a large sample of emerging adults (ages 21-25) using a cross-sectional design. A secondary objective was to examine age of cannabis initiation as a moderator.

METHODS

Participants were high-risk drinking emerging adults (n = 598) reporting past-month cannabis use in the following categories: 1) non-users (i.e., never or not in the past month; n = 276), 2) occasional users (i.e., monthly or weekly users; n = 201), and 3) daily users (n = 121). Categorical comparisons were conducted on working memory, attention, behavioral inhibition, delay and probability discounting, verbal intelligence, and ADHD symptoms. Complementary dimensional analyses examined cannabis severity in relation to neurocognition using regressions. Covariates were age, race, sex, income, years of education, tobacco use, and alcohol use.

RESULTS

Frequency of cannabis use was significantly associated with poorer working memory performance, more impulsive delay discounting, and greater endorsement of ADHD symptoms, but not other domains. Effect sizes were small and poorer performance was selectively present among daily, not occasional, cannabis users. Earlier age of initiation was not independently or interactively associated with neurocognitive performance.

CONCLUSIONS

Daily cannabis use was selectively adversely associated with aspects of memory, impulsivity, and subjective attentional functioning, but most cognitive indicators were not implicated, and evidence of amplification by earlier age of initiation was not observed. Ascertaining causal versus consequential roles of cannabis in neurocognitive functioning is an important priority.

Initiation of Moderately Frequent Cannabis use in Adolescence and Young Adulthood is Associated with Declines in Verbal Learning and Memory: A Longitudinal Comparison of Pre- versus Post-Initiation Cognitive Performance

OBJECTIVE

Cannabis use is associated with relative cognitive weaknesses as observed by cross-sectional as well as longitudinal research. Longitudinal studies, controlling for relevant confounds, are necessary to differentiate premorbid from post-initiation contributions to these effects.

METHODS

We followed a sample of adolescents and young adults across ten years. Participants provided neurocognitive data and substance use information at two-year intervals. Participants who initiated cannabis and/or alcohol use were identified (n = 86) and split into alcohol-only initiators (n = 39) and infrequent (n = 29) and moderately frequent (n = 18) cannabis initiators. Participants completed the Rey Auditory Verbal Learning Task (RAVLT) and the Iowa Gambling Task (IGT). Group differences before and after substance use initiation and the extent to which alcohol, nicotine, and cannabis use frequencies contributed to cognitive functions over time were examined.

RESULTS

After controlling for parental education, RAVLT new learning was worse in moderately frequent cannabis users prior to use initiation. RAVLT total learning and delayed recall showed significant declines from pre- to post-initiation in moderately frequent cannabis users. Regression analyses confirmed that frequencies of cannabis, but not alcohol, use contributed to post-initiation variations. Nicotine use showed an independent negative association with delayed memory. Findings for the IGT were not significant.

CONCLUSIONS

Verbal learning and memory may be disrupted following the initiation of moderately frequent cannabis use while decreased new learning may represent a premorbid liability. Our use of a control group of alcohol-only users adds interpretive clarity to the findings and suggests that future studies should carefully control for comorbid substance use.

Daily, but not occasional, cannabis use is selectively associated with more impulsive delay discounting and hyperactive ADHD symptoms in binge-drinking young adults

RATIONALE

There is increasing interest in and evidence for the negative impacts of cannabis use in cognitive performance and symptoms of attention-deficit/hyperactivity disorder (ADHD), with age of first cannabis use as a potential amplifier of these associations. However, the existing literature is inconsistent, which may be due to methodological limitations, including small sample sizes.

OBJECTIVE

To examine current cannabis use and age of first cannabis use in relation to neurocognitive task performance and ADHD symptoms in a large sample of binge-drinking young adults.

METHODS

Participants were young adults (N=730, M age=21.44, 52.6% female) assessed for current cannabis use, neurocognitive task performance, and ADHD symptoms. Three-group ANCOVAs compared individuals reporting frequent (daily/multiple times daily), occasional (weekly/monthly), or no cannabis use.

RESULTS

Covarying alcohol use, tobacco use, age, sex, income, and education, daily cannabis users exhibited significantly more impulsive delay discounting and hyperactive-impulsive ADHD symptoms compared to both other groups. However, cannabis use was not associated with inattentive ADHD symptoms, verbal intelligence, working memory, probability discounting, short-term verbal memory, or behavioral inhibition. Age of initiation of cannabis use exhibited neither main effects nor interactions in relation to any domains of cognitive performance or ADHD symptomatology.

CONCLUSIONS

The current findings provide support for a link between cannabis use in relation to immediate reward preference and symptoms of hyperactive-impulsive ADHD in young adults, but only among frequent users. No other neurocognitive domains exhibited associations with cannabis and age of first use was neither independently nor interactively associated with cognitive outcomes.

Altered cerebellar-cortical resting-state functional connectivity in cannabis users

BACKGROUND

Cannabis use has been associated with abnormalities in cerebellar mediated motor and non-motor (i.e. cognition and personality) phenomena. Since the cerebellum is a region with high cannabinoid type 1 receptor density, these impairments may reflect alterations of signaling between the cerebellum and other brain regions.

AIMS

We hypothesized that cerebellar-cortical resting-state functional connectivity (rsFC) would be altered in cannabis users, relative to their non-using peers. It was also hypothesized that differences in rsFC would be associated with cannabis use features, such as age of initiation and lifetime use.

METHODS

Cerebellar-cortical and subcortical rsFCs were computed between 28 cerebellar lobules, defined by a spatially unbiased atlas template of the cerebellum, and individual voxels in the cerebral regions, in 41 regular cannabis users (20 female) and healthy non-using peers (N = 31; 18 female). We also investigated associations between rsFC and cannabis use features (e.g. lifetime cannabis use and age of initiation).

RESULTS

Cannabis users demonstrated hyperconnectivity between the anterior cerebellar regions (i.e. lobule I-IV) with the posterior cingulate cortex, and hypoconnectivity between the rest of the cerebellum (i.e. Crus I and II, lobule VIIb, VIIIa, VIIIb, IX, and X) and the cortex. No associations were observed between features of cannabis use and rsFC.

CONCLUSIONS

Cannabis use was associated with altered patterns of rsFC from the cerebellum to the cerebral cortex which may have a downstream impact on behavior and cognition.

Female Sex as a Protective Factor in the Effects of Chronic Cannabis Use on Verbal Learning and Memory

OBJECTIVE

The variability of findings in studies examining the effects of chronic cannabis use on neuropsychological functioning highlights the importance of examining contributing factors. Few studies examine the role of sex in the relationship between cannabis and neuropsychological functioning, despite known neurobiological structural differences between males and females. This study examined whether males and females experience differential cognitive effects of chronic cannabis use.

METHOD

Chronic cannabis users (3+ days per week for >12 months, n = 110, 72% male) and non-users (n = 71, 39% male) completed a neuropsychological test battery. Two multivariate analyses of covariance (MANCOVAs) examined for sex differences in performance within users and non-users on neuropsychological tests, controlling for potential confounding variables. Bonferroni corrections were applied to adjust for multiple comparisons.

RESULTS

Male and female cannabis users did not differ in cannabis use variables. Female cannabis users performed better than males on multiple subtests of the California Verbal Learning Test-II (CVLT-II), a verbal learning and memory test. Male cannabis users performed better than female users on Trial 1 of the CVLT-II (p = .002), and Trail Making Test B (p = .001), which measure attention and cognitive flexibility, respectively. Non-user males and females performed comparably, with the exception of Trail Making Test B (p = .001).

CONCLUSIONS

Results suggest that chronic cannabis use differentially impacts males and females, with females exhibiting better verbal learning and memory despite males demonstrating better attention and cognitive flexibility. Further research is needed to understand the potential protective mechanism of female sex on learning and memory effects of cannabis use.

Effects of repeated adolescent exposure to cannabis smoke on cognitive outcomes in adulthood

BACKGROUND

Cannabis (marijuana) is the most widely used illicit drug in the USA, and consumption among adolescents is rising. Some animal studies show that adolescent exposure to delta 9-tetrahydrocannabinol or synthetic cannabinoid receptor 1 agonists causes alterations in affect and cognition that can persist into adulthood. It is less clear, however, whether similar alterations result from exposure to cannabis via smoke inhalation, which remains the most frequent route of administration in humans.

AIMS

To begin to address these questions, a rat model was used to determine how cannabis smoke exposure during adolescence affects behavioral and cognitive outcomes in adulthood.

METHODS

Adolescent male Long-Evans rats were assigned to clean air, placebo smoke, or cannabis smoke groups. Clean air or smoke exposure sessions were conducted daily during adolescence (from P29-P49 days of age ) for a total of 21 days, and behavioral testing began on P70.

RESULTS

Compared to clean air and placebo smoke conditions, cannabis smoke significantly attenuated the normal developmental increase in body weight, but had no effects on several measures of either affect/motivation (open field activity, elevated plus maze, instrumental responding under a progressive ratio schedule of reinforcement) or cognition (set shifting, reversal learning, intertemporal choice). Surprisingly, however, in comparison to clean air controls rats exposed to either cannabis or placebo smoke in adolescence exhibited enhanced performance on a delayed response working memory task.

CONCLUSIONS

These findings are consistent with a growing body of evidence for limited long-term adverse cognitive and affective consequences of adolescent exposure to relatively low levels of cannabinoids.

Sex Differences in Neuropsychological Functioning are Domain-Specific in Adolescent and Young Adult Regular Cannabis Users

OBJECTIVE

Adolescence into young adulthood represents a sensitive period in which brain development significantly diverges by sex. Regular cannabis use by young people is associated with neuropsychological vulnerabilities, but the potential impact of sex on these relationships is unclear.

METHOD

In a cross-sectional study, we examined sex differences in multi-domain neuropsychological functioning using the Cambridge Neuropsychological Test Automated Battery (CANTAB) and tested whether sex moderated the relationship between cognitive performance and age of initiation, frequency of cannabis use, amount of cannabis use, and withdrawal symptoms in at least weekly adolescent and young adult cannabis users (n = 171; aged 13-25 years; 46.2% female).

RESULTS

Male cannabis users had poorer visual recognition memory and female cannabis users showed worse attention and executive functions, with medium to large effect sizes. These sex effects persisted, when controlling for age, IQ, amount of alcohol and nicotine use, mood and anxiety symptoms, emotional stability and impulsive behavior. Earlier age of initiated use and more use were associated with worse attentional functions in females, but not males. More use was more strongly associated with worse episodic memory in males than in females. More use was associated with poorer learning in males only.

CONCLUSIONS

Domain-specific patterns of neuropsychological performance were found by sex, such that males showed poorer visual memory and females showed worse performance on measures of attention (sustained visual, multitasking) and executive functioning (spatial planning/working memory subdomains). Larger studies including healthy controls are needed to determine if the observed sex differences are more exaggerated relative to non-users.

Predictors of cannabis and tobacco co-use in youth: exploring the mediating role of age at first use in the population assessment of tobacco health (PATH) study

Background

Adolescents often use substances such as tobacco and cannabis. Co-use of these substances can lead to physical, mental, and psychosocial difficulties beyond that which would be anticipated by simple additivity of their individual effects.

Methods

We aimed to examine the mediating role of age at first use of cannabis or tobacco (AU) between youth factors of internalizing, externalizing, and sensation seeking and two co-use outcomes (lifetime; last 30 days). Path analytic modeling using data from youth age 12–17 who had tried cannabis or tobacco at least once in their lives and participated in the Population Assessment of Tobacco Health (PATH) waves one and two (collected 2013–2015; n=3,847; approximately 46% female) study allowed us to examine these relationships.

Results

The lifetime use model indicated significant direct (internalizing (B = 0.18), externalizing (B = 0.30), sensation seeking (B = 0.15)) and indirect relationships (internalizing (B = 0.18), externalizing (B = 0.33), sensation seeking (B = 0.10)) between each of the three youth factors, the mediator (AU) and the lifetime co-use outcome (p < 0.05 for all). A direct relationship between AU and lifetime co-use was also observed (B = − 1.54). In the past 30-day use model, significant direct paths from AU (B = − 0.49) and sensation seeking (B = 0.06) to past 30-day use were present (p < 0.05 for all).

Discussion

Examination of mediation by AU in the relationships between youth factors and youth co-use of cannabis and tobacco is an important step in understanding these complex relationships. This study is strengthened by the use of a large, nationally representative sample, yet is limited by several factors, such as the use of a secondary dataset and the use of youth self-report.

Conclusions

Based on the findings, programs or interventions targeting youth factors of internalizing, externalizing, and sensation seeking as well as interventions aiming to stave off AU should promote decreased tobacco and cannabis co-use. Sensation seeking and AU appear to be the most influential factors and should be considered when developing and promoting prevention policies/programs for higher risk youth populations.

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.

Associations between adolescent cannabis use and young-adult functioning in three longitudinal twin studies

Observational studies have linked cannabis use to an array of negative outcomes, including psychiatric symptoms, cognitive impairment, and educational and occupational underachievement. These associations are particularly strong when cannabis use occurs in adolescence. Nevertheless, causality remains unclear. The purpose of the present study was thus to examine associations between prospectively assessed adolescent cannabis use and young-adult outcomes (psychiatric, cognitive, and socioeconomic) in three longitudinal studies of twins (n = 3,762). Twins reporting greater cumulative cannabis use in adolescence reported higher levels of psychopathology as well as poorer socioeconomic outcomes in young adulthood. However, cannabis use remained associated only with socioeconomic outcomes (i.e., educational attainment, occupational status, and income) in monozygotic-cotwin control analyses, which account fully for shared genetic and environmental confounding. Follow-up analyses examining associations between twin differences in adolescent cannabis use and longitudinal change in academic functioning during the middle- and high-school years provided a possible mechanism for these associations, indicating that greater cannabis use during this period was associated with decreases in grade point average and academic motivation as well as increases in academic problem behavior and school disciplinary problems. Our findings thus suggest that cannabis use in adolescence has potentially causal, deleterious effects on adolescent academic functioning and young-adult socioeconomic outcomes despite little evidence suggesting a strong, causal influence on adult mental health or cognitive ability.

Familial factors may not explain the effect of moderate-to-heavy cannabis use on cognitive functioning in adolescents: a sibling-comparison study

AIMS

To examine whether moderate adolescent cannabis use has neurocognitive effects that are unexplained by familial confounds, which prior family-controlled studies may not have identified.

DESIGN

A quasi-experimental, sibling-comparison design was applied to a prospective, observational study of adolescents with moderate cannabis use. Participants were recruited from 2001 to 2006 (mean age = 17 years). A second wave of data was collected from 2008 to 2013 (mean age = 24 years).

SETTING

Two US metropolitan communities.

PARTICIPANTS

A total of 1192 adolescents from 596 families participated in this study. Participants were primarily male (64%) and racially and ethnically diverse (non-Hispanic white = 45%). A sibling in each family was a clinical proband identified due to delinquent behaviors. Whereas prior family-controlled studies have used samples of primarily infrequent cannabis users (mean = 1-2 days/month), participants here endorsed levels of cannabis use comparable to findings from epidemiological cohort studies (mean = 7-9 days/month).

MEASUREMENTS

Semi-structured clinical interviews assessed drug use, and a neuropsychological battery assessed cognitive abilities. Covariates included age at assessment, gender and alcohol use.

FINDINGS

After correcting for multiple testing, a greater frequency and earlier onset of regular cannabis use were associated with poorer cognitive performance, specifically on tests of verbal memory. Further, after accounting for familial factors shared by siblings and alcohol use, poorer verbal memory performance was still associated with greater life-time frequency of cannabis use at wave 1 [b = -0.007 (-0.002, -0.012), adjusted P = 0.036]; earlier cannabis use at wave 2 [b = -0.12 (-0.05, -0.19), adjusted P = 0.006; b = -0.14 (-0.06, -0.23), adjusted P = 0.006]; and greater frequency of past 6 months use at wave 2 [b = -0.02 (-0.01, -0.03), adjusted P = 0.002; b = -0.02 (-0.01, -0.03), adjusted P = 0.008].

CONCLUSIONS

Moderate adolescent cannabis use may have adverse effects on cognitive functioning, specifically verbal memory, that cannot be explained by familial factors.

Associations of Regular Marijuana Use by Adolescent Boys With Verbal Memory and Perseveration

Many American and Dutch adolescents use marijuana regularly. There is concern that such use may impair cognitive function more in adolescents than adults. We examined effects of regular marijuana use on long-term memory and perseveration among American and Dutch adolescents. We administered Buschke's Selective Reminding Test (BSRT) to assess long-term memory and the Wisconsin Card Sorting Test (WCST) to assess perseveration in male teenagers. Usable test data were obtained for 12 American marijuana users, 13 American controls, 9 Dutch marijuana users, and 12 Dutch controls. In BSRT, users showed lower overall long-term storage than controls (adjusted means ± SE's for numbers of words per trial of 9.4 ± 0.2, 13.4 ± 0.3, 11.7 ± 0.2, and 12.4 ± 0.2 for American users, Dutch users, American controls, and Dutch controls, respectively). Marijuana was associated with memory effects only in American, not Dutch, users. Bivariate Pearson correlations for American and Dutch users combined showed associations of lower total recall with more uses in the previous year and lifetime (r = -0.61 and r = -0.53, respectively); and more perseverative errors with more uses in the previous year (r = 0.55). Some findings were consistent with the possibility that regular adolescent marijuana use causes deficits in cognition, especially memory. However, a causal interpretation cannot be inferred from our findings and is challenging to reconcile with the observation of memory deficits only in American users. Our study was novel in examining the influence of nationality on marijuana's cognitive effects. More studies of this topic should compare effects across nationalities or cultures.