Neuropsychological deficits associated with cannabis use in young adults

Acute effects of different types of cannabis on young adult and adolescent resting-state brain networks

Adolescence is a time of rapid neurodevelopment and the endocannabinoid system is particularly prone to change during this time. Cannabis is a commonly used drug with a particularly high prevalence of use among adolescents. The two predominant phytocannabinoids are Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD), which affect the endocannabinoid system. It is unknown whether this period of rapid development makes adolescents more or less vulnerable to the effects of cannabis on brain-network connectivity, and whether CBD may attenuate the effects of THC. Using fMRI, we explored the impact of vaporized cannabis (placebo, THC: 8 mg/75 kg, THC + CBD: 8 mg/75 kg THC & 24 mg/75 kg CBD) on resting-state networks in groups of semi-regular cannabis users (usage frequency between 0.5 and 3 days/week), consisting of 22 adolescents (16-17 years) and 24 young adults (26-29 years) matched for cannabis use frequency. Cannabis caused reductions in within-network connectivity in the default mode (F[2,88] = 3.97, P = 0.022, η² = 0.018), executive control (F[2,88] = 18.62, P < 0.001, η² = 0.123), salience (F[2,88] = 12.12, P < 0.001, η² = 0.076), hippocampal (F[2,88] = 14.65, P < 0.001, η² = 0.087), and limbic striatal (F[2,88] = 16.19, P < 0.001, η² = 0.102) networks compared to placebo. Whole-brain analysis showed cannabis significantly disrupted functional connectivity with cortical regions and the executive control, salience, hippocampal, and limbic striatal networks compared to placebo. CBD did not counteract THC's effects and further reduced connectivity both within networks and the whole brain. While age-related differences were observed, there were no interactions between age group and cannabis treatment in any brain network. Overall, these results challenge the assumption that CBD can make cannabis safer, as CBD did not attenuate THC effects (and in some cases potentiated them); furthermore, they show that cannabis causes similar disruption to resting-state connectivity in the adolescent and adult brain.

Cannabinoids and Multiple Sclerosis: A Critical Analysis of Therapeutic Potentials and Safety Concerns

Multiple sclerosis (MS) is a complicated condition in which the immune system attacks myelinated axons in the central nervous system (CNS), destroying both myelin and axons to varying degrees. Several environmental, genetic, and epigenetic factors influence the risk of developing the disease and how well it responds to treatment. Cannabinoids have recently sparked renewed interest in their therapeutic applications, with growing evidence for their role in symptom control in MS. Cannabinoids exert their roles through the endogenous cannabinoid (ECB) system, with some reports shedding light on the molecular biology of this system and lending credence to some anecdotal medical claims. The double nature of cannabinoids, which cause both positive and negative effects, comes from their actions on the same receptor. Several mechanisms have been adopted to evade this effect. However, there are still numerous limitations to using cannabinoids to treat MS patients. In this review, we will explore and discuss the molecular effect of cannabinoids on the ECB system, the various factors that affect the response to cannabinoids in the body, including the role of gene polymorphism and its relation to dosage, assessing the positive over the adverse effects of cannabinoids in MS, and finally, exploring the possible functional mechanism of cannabinoids in MS and the current and future progress of cannabinoid therapeutics.

Problem gambling severity, gambling behavior, substance use, and mental health in gamblers who do and do not use cannabis: Evidence from a Canadian national sample

INTRODUCTION

Cannabis use frequently co-occurs with gambling, and evidence indicates that both acute and chronic cannabis use may influence gambling behavior. The primary aim of the present study was to further contribute to the literature on this relationship by examining data collected from a Canadian national study of gambling.

METHODS

Respondents consisted of 10,054 Canadian gamblers recruited from Leger Opinion's (LEO) online panel. In this study, gamblers who used cannabis were compared with non-users across a number of gambling as well as demographic and mental health variables.

RESULTS

Of the total sample, 25.4 % reported past 12-month cannabis use. Among the 2,553 cannabis-users, 21.3 % reported daily use, and 69.9 % reported using once a month or more. A total of 56.2 % indicated they had used cannabis while gambling in the past 12 months. Bivariate analysis found significant differences between cannabis use and non-use on numerous demographic, mental health, and gambling-related variables. Individuals with greater problem gambling severity scores, more hours gambling, and a larger range of gambling activities were more likely to endorse using cannabis. Hierarchical logistic regression revealed that tobacco use, and having experienced significant child abuse were predictors of cannabis use. Non-use of cannabis was associated with older age, less engagement in online gambling, and being less likely to consume alcohol.

CONCLUSION

The present findings both corroborate previous studies and expand upon the relationship between cannabis and gambling.

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.

Age of gambling onset and resultant gambling behavior during young adulthood in the United States

BACKGROUND AND OBJECTIVES

Previous research has examined how the age at which an individual first gambles (age of gambling onset) correlates with problematic behavior later in life, such as problematic alcohol or substance use; however, much less is known about how age of gambling onset, particularly as a child or as a young adult, might influence future gambling. We assessed how self-reported age of gambling onset may have shaped more recent gambling and propensity to take risks.

METHODS

We analyzed questionnaire data and neurocognitive assessment data collected from young adults in the United States (n = 579) and conducted ordinal logistic regression to model our study variables.

RESULTS

Upon examining three distinct age categories (under 18, 18-20, 21, and over), we found that earlier age of gambling onset was significantly associated with betting a higher overall proportion during a neurocognitive task. CONCLUSIONS AND SCIENTIFIC SIGNIFICANCE: Gambling more points on a laboratory-based task was correlated to earlier age of gambling onset. There were no statistically significant associations between age of gambling onset and severity of recent pathological gambling, nor gambling expenditure in the past year, nor gambling frequency in the past week. Future longitudinal study should discern the causality of these findings in both directions and ascertain whether these findings can be extended to older and clinical populations. Future work should explore other variables, such as ethnicity and socioeconomic background, that may be relevant to understanding variations in age of gambling onset and its repercussions.

Effects of SativexⓇ on cognitive function in patients with multiple sclerosis: A systematic review and meta-analysis

BACKGROUND

Cognitive impairment is a common manifestation of multiple sclerosis (MS).

OBJECTIVE

To assess by systematic review and meta-analysis available evidence regarding the impact of nabiximols oromucosal spray on cognition in patients with MS.

METHODS

A systematic literature search of clinical studies (all types, any comparator) that measured cognitive function in patients with MS spasticity treated with nabiximols. Meta-analysis for cognitive endpoints was not possible due to heterogenous measurement instruments and outcomes. Meta-analysis was performed for adverse events (AEs) of special interest (cognition disorders) reported in randomized controlled trials (RCTs) of nabiximols versus placebo in patients with MS (with or without spasticity). Certainty of evidence and risk of bias were assessed.

RESULTS

Seven clinical studies (three RCTs) directly assessing cognitive function were included in the qualitative analysis. There was no consistent evidence to suggest that nabiximols causes cognitive impairment as assessed by a range of specific psychometric instruments across cognitive domains. Thirteen double-blind, placebo-controlled RCTs (nabiximols, n = 964; placebo, n = 904) were included in the meta-analysis of cognitive AEs. Most cognitive AEs (30 of 32 events, 93.8%) reported with nabiximols in MS patients occurred with not in-label use, i.e., dosage >12 sprays per day and/or not administered primarily for treatment of spasticity.

CONCLUSIONS

Within the limitations of the review, we can conclude that no detrimental effects of nabiximols on cognitive function were observed in patients with MS spasticity during up to 12 months follow-up and that cognitive AEs were rare and occurred only when nabiximols was not used according to its approved label.

Cannabis Practices Among a Gender-Diverse Sample of Young Adults

Background

Gender is an important factor in understanding cannabis patterns, yet few studies have explored cannabis patterns among gender minority (GM) individuals - particularly among high-risk age groups including young adults. The evolving cannabis market is reshaping typical patterns of cannabis use in the U.S. The combination of these factors warrants increased efforts to examine cannabis practices in gender-diverse samples.

Methods

Online survey participants between 18-34 years (N=2377) from the U.S. provided information on cannabis practices from May - July 2021. Gender differences across several cannabis outcomes (onset, methods of consumption, product potency, frequency, and quantity) were assessed. Bivariate tests and multiple regression models examined associations between gender (cisgender men: n=1020; cisgender women: n=1178; and GM: n=179) and cannabis outcomes adjusting for sociodemographic characteristics.

Results

In regression models adjusted for sociodemographic characteristics, GM identity was associated with later age of onset and lower likelihood of daily use compared to cisgender men and women. Identifying as GM or cisgender woman was associated with fewer lifetime methods of consumption and lower plant and concentrate potency usage.

Conclusions

Findings provide initial insights into potential gender differences in cannabis practices from a sample of heavy cannabis users. GM young adults report use patterns indicative of lower risk compared to cisgender men and women in our sample. Future investigations of gender differences in cannabis use that explore specific gender minority categories and that include alternative sampling strategies are needed to better understand differential risks associated with gender.

The CannTeen study: verbal episodic memory, spatial working memory, and response inhibition in adolescent and adult cannabis users and age-matched controls

BACKGROUND

Preclinical and human studies suggest that adolescent cannabis use may be associated with worse cognitive outcomes than adult cannabis use. We investigated the associations between chronic cannabis use and cognitive function in adolescent and adult cannabis users and controls. We hypothesised user-status would be negatively associated with cognitive function and this relationship would be stronger in adolescents than adults.

METHODS

As part of the 'CannTeen' project, this cross-sectional study assessed cognitive performance in adolescent cannabis users (n = 76; 16-17-year-olds), adolescent controls (n = 63), adult cannabis users (n = 71; 26-29-year-olds) and adult controls (n = 64). Users used cannabis 1-7 days/week. Adolescent and adult cannabis users were matched on cannabis use frequency (4 days/week) and time since last use (2.5 days). Verbal episodic memory (VEM) was assessed using the prose recall task, spatial working memory (SWM) was assessed using the spatial n-back task, and response inhibition was assessed with the stop-signal task. Primary outcome variables were: delayed recall, 3-back discriminability, and stop signal reaction time, respectively.

RESULTS

Users had worse VEM than controls (F(1,268) = 7.423, p = 0.007). There were no significant differences between user-groups on SWM or response inhibition. Null differences were supported by Bayesian analyses. No significant interactions between age-group and user-group were found for VEM, SWM, or response inhibition.

CONCLUSIONS

Consistent with previous research, there was an association between chronic cannabis use and poorer VEM, but chronic cannabis use was not associated with SWM or response inhibition. We did not find evidence for heightened adolescent vulnerability to cannabis-related cognitive impairment.

Cannabis use and sexual risk among MSM who drink: Understanding why more frequent cannabis users may engage in higher rates of condomless sex

BACKGROUND

Condomless anal intercourse (CAI) is the major risk factor for HIV transmission among men who have sex with men (MSM). MSM who are heavier cannabis users engage in CAI more frequently. However, little is known about the processes that may underlie this association. This study sought to understand the potential role of condom attitudes and condom-related planning in the association between cannabis use and CAI.

METHODS

This is a secondary data analysis of a study on alcohol use and sexual decision-making among MSM. Two hundred and fifty-eight MSM with moderate to heavy drinking were enrolled. Measures included CAI, cannabis use, attitudes about the influence of condoms on sexual pleasure, condom use planning, age, heavy episodic drinking, and use of pre-exposure prophylaxis (PrEP).

RESULTS

We conducted a negative binomial regression analysis controlling for age, PrEP, and heavy episodic drinking. Cannabis use frequency was a significant predictor of CAI (b =.333, p < .001). Indirect effects showed that while heavier cannabis users exhibited less condom-related planning (b = -0.106, p = 0.015) and more negative attitudes toward the impact of condom use on pleasure (b= -0.177, p = 0.004), cannabis use had a significant indirect effect on CAI only through attitude ratings.

CONCLUSIONS

MSM who are heavier cannabis users engage in more frequent CAI and exhibit an indirect effect on CAI through negative attitudes toward the impact of condoms on pleasure. These findings suggest the potential importance of addressing these condom attitudes in HIV-prevention interventions among MSM who use cannabis.

Risky decision-making as an antecedent or consequence of adolescent cannabis use: findings from a 2-year longitudinal study

BACKGROUND AND AIMS

Although poor decision-making (DM) has been correlated with problematic cannabis use (CU), cross-sectional designs make it difficult to determine whether poor DM represents an antecedent and/or consequence of CU. The current study measured bidirectional associations between CU and DM among adolescents over 2 years and compared these findings to those observed with episodic memory, which is consistently reported as a consequence of CU. We also measured the role of DM as a risk factor for cannabis use disorder (CUD) onset.

DESIGN

Two-year longitudinal study with five bi-annual assessments.

PARTICIPANTS

Participants were 401 adolescents aged 14-17 years at baseline.

SETTING

Miami, Florida, USA.

MEASUREMENTS

CU frequency and CUDs were assessed at each time-point through the Drug Use History Questionnaire and Structured Clinical Interview for DSM-IV, respectively. Neurocognition was assessed at odd time-points throughout the Iowa Gambling Task, Game of Dice Task and Cups Task [decision-making (DM)] and the Wechsler Memory Scale IV and California Verbal Learning Test II (episodic memory). We used latent growth curve modeling to examine bidirectional influences between CU and neurocognition over time. We applied discrete time survival analyses to determine whether baseline DM predicted CUD onset.

FINDINGS

Greater lifetime CU frequency was associated with poorer episodic memory at baseline (bs = -14.84, -16.44, Ps = 0.038, 0.021). Greater CU escalation predicted lesser gains in immediate episodic memory (b = -0.05, P = 0.020). Baseline DM did not predict CU escalation (b = 0.07, P = 0.421), nor did escalation in CU predict changes in DM (b = 0.02, P = 0.352). Baseline DM also did not predict CUD onset (adjusted OR = 1.01, 95% confidence interval = 0.98-1.06).

CONCLUSIONS

This study replicates findings that poorer episodic memory in adolescents appears to be a consequence of cannabis use, even among adolescents at earlier stages of use. Poor decision-making does not appear to be either a consequence of or a risk factor for escalating cannabis use or onset of cannabis use disorder among adolescents.

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.

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.

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.

Assessment of neuropsychological impairments in regular cannabis users

BACKGROUND

Cannabis is the most widely used illicit drug in the world. It is responsible for cognitive dysfunction of memory, speed of information processing, attention, and executive functions. Cognitive performance depends on the level of study, tolerance, and duration of abstinence from cannabis use. This study analyses cognitive function in a large population of regular cannabis consumers taking into account level of education.

METHODS

A battery of neuropsychological tests using the Cambridge Neuropsychological Test Automated Battery was performed on a population of 58 cannabis users categorized into two groups according to their level of education with a threshold of 12 years of study, and 25 non-users.

RESULTS

In Attention Switching Task percent correct trials, significant differences were found between the group of cannabis smokers with less than 12 years of study and the non-smoker group (P=0.022), and between the cannabis users with more than 12 years of study and the non-smoker group (P=0.008). A significantly lower performance in the Rapid Visual Information Processing (Mean latency, Probability of hit, Total hits, Total misses, Correct rejections) was found in the cannabis users with less than 12 years of study compared with the non-user group.

CONCLUSION

In our population, chronic cannabis users presented divided and sustained attention and working memory disorders. Rapid Visual Information Processing performance may be influenced by education level in cannabis smokers.

Altered fronto-occipital connectivity during visual selective attention in regular cannabis users

RATIONALE AND OBJECTIVES

Cognitive processing impairments have been associated with acute cannabis use, but there is mixed evidence regarding the cognitive effects of chronic cannabis use. Several neuroimaging studies have noted selective-attention processing differences in those who chronically use cannabis, but the neural dynamics governing the altered processing is unclear.

METHODS

Twenty-four adults reporting at least weekly cannabis use in the past 6 months on the Cannabis Use Disorder Identification Test - Revised were compared to 24 demographically matched controls who reported no prior cannabis use. All participants completed a visual selective attention processing task while undergoing magnetoencephalography. Time-frequency windows of interest were identified using a data-driven method, and spectrally specific neural activity was imaged using a beamforming approach.

RESULTS

All participants performed within normal range on the cognitive task. Regular cannabis users displayed an aberrant cognitive interference effect in the theta (4-8 Hz) frequency range shortly after stimulus onset (i.e., 0-250 ms) in the right occipital cortex. Cannabis users also exhibited altered functional connectivity between the right prefrontal cortex and right occipital cortices in comparison to controls.

CONCLUSIONS

Individuals with a history of regular cannabis use exhibited abnormal theta interference activity in the occipital cortices, as well as altered prefrontal-occipital functional connectivity in the theta range during a visual selective attention task. Such differences may reflect compensatory processing, as these participants performed within normal range on the task. Understanding the neural dynamics in chronic, regular cannabis users may provide insight on how long-term and/or frequent use may affect neural networks underlying cognitive processes.

Acute effects of partial CB1 receptor agonists on cognition - A meta-analysis of human studies

BACKGROUND

Impairment in cognition is frequently associated with acute cannabis consumption. However, some questions remain unanswered as to which deficits are most prominent and which demographic groups are most vulnerable.

METHODS

A literature search yielded 52 experimental studies of acute administration of partial CB₁ receptor agonists (i.e. cannabis, THC, and nabilone) that assessed cognitive dysfunction in 1580 healthy volunteers. Effect size estimates were calculated using the Comprehensive Meta-Analysis for the following six cognitive domains: attention, executive functions, impulsivity, speed of processing, verbal learning/memory, and working memory.

RESULTS

There were small-to-moderate impairments across all cognitive domains. Deficits in verbal learning/memory and working memory were more prominent, whereas attention and impulsivity were the least affected. Meta-regression analysis revealed that the greater the male ratio is in a sample, the greater the negative effect of cannabinoids on speed of processing and impulsivity. Analysis of route of administration showed that the deficits in speed of processing were smaller in the oral, relative to smoking, vaping, and intravenous administration studies. A publication bias was observed.

DISCUSSION

Verbal learning/memory and working memory are most prominently affected by acute administration of partial CB₁ receptor agonists. The results are consistent with the residual cognitive effects that have been documented among chronic cannabis users.

BOLD responses to inhibition in cannabis-using adolescents and emerging adults after 2 weeks of monitored cannabis abstinence

RATIONALE

Previous studies have suggested that chronic cannabis use has been associated with increased blood oxygen level-dependent (BOLD) response during a response inhibition task; however, these studies primarily included males.

OBJECTIVES

We investigated whether gender moderated the effects of cannabis use on BOLD response and behavioral performance during a Go-NoGo task in adolescents and young adults following 2 weeks of monitored abstinence.

METHODS

Participants included 77 16-26-year olds (MJ = 36, controls = 41). An emotion-based Go-NoGo task required participants to inhibit their response during a calm face. A whole-brain analysis looked at differences between cannabis group, gender, and their interaction.

RESULTS

Significant greater BOLD responses were observed in cannabis users compared with that in controls in the left frontal cortex, left cingulate cortex, and the left thalamus during correct response inhibitions; gender did not moderate these effects.

CONCLUSION

Supporting previous research, cannabis users showed greater BOLD responses in core areas associated with response inhibition during a Go-NoGo task, even after a minimum of 2 weeks of abstinence.

Disentangling the effects of cannabis and cigarette smoking on impulsivity

BACKGROUND

Cannabis smoking and cigarette smoking often co-occur, yet limited research has investigated the potentially different role impulsivity may play when these behaviours occur in isolation, compared with in combination.

AIMS

This study examined trait and behavioural impulsivity as a function of both cigarette and cannabis smoking.

METHODS

Trait impulsivity (BIS-11) was compared between 44 non-smokers, 76 cigarette only, 47 cannabis only and 58 cannabis plus cigarette smokers. The effects of cigarette and cannabis smoking on behavioural impulsivity (stop-signal and information sampling tasks) were then assessed in 87 of these participants during a laboratory session.

RESULTS

Trait impulsivity was significantly higher in cigarette smokers than non-smokers, irrespective of cannabis use, except for motor impulsivity, where cigarette smoking was only associated with elevated trait impulsivity in non-smokers of cannabis. Dimensions of trait impulsivity were significantly positively related to cigarette smoking frequency and nicotine dependence, but not to cannabis smoking frequency or dependence. Smoking cigarettes or cannabis was associated with significantly impaired reflection impulsivity relative to not smoking either substance. However, no additional increases in reflection impulsivity were observed in those who smoked both cigarettes and cannabis. No group differences in response inhibition were detected.

CONCLUSIONS

Heightened trait impulsivity appears to be uniquely related to cigarette smoking, whilst the smoking of cigarettes or cannabis is associated with impairments in reflection impulsivity. Improved outcomes for treating cannabis dependence may result from encouraging concomitant cigarette smokers to cease using both drugs simultaneously in order to reduce heightened impulsivity and risk of relapse.

Different Effects of Cannabis Abuse on Adolescent and Adult Brain

Cannabis abuse is a common phenomenon among adolescents. The dominant psychoactive substance in Cannabis sativa is tetrahydrocannabinol (THC). However, in the past 40 years the content of the psychoactive ingredient THC in most of the preparations is not constant but has increased due to other breeding and culturing conditions. THC acts as the endocannabinoids at CB1 and CB2 receptors but pharmacologically can be described as a partial (not a pure) agonist. Recent evidence shows that activation of the CB1 receptor by THC can diminish the production of neuronal growth factor in neurons and affect other signalling cascades involved in synapsis formation. Since these factors play an important role in the brain development and in the neuronal conversion processes during puberty, it seems reasonable that THC can affect the adolescent brain in another manner than the adult brain. Accordingly, in adolescent cannabis users structural changes were observed with loss of grey matter in certain brain areas. Moreover, recent studies show different effects of THC on adolescent and adult brains and on behaviour. These studies indicate that early THC abuse can result in neuropsychological deficits. This review gives an overview over the present knowledge in this field.

Heavy cannabis use, dependence and the brain: a clinical perspective

AIMS

To summarize and evaluate our knowledge of the relationship between heavy cannabis use, cannabis use disorder (CUD) and the brain.

METHODS

Narrative review of relevant literature identified through existing systematic reviews, meta-analyses and a PubMed search. Epidemiology, clinical representations, potential causal mechanisms, assessments, treatment and prognosis are discussed.

RESULTS

Although causality is unclear, heavy and dependent cannabis use is consistently associated with a high prevalence of comorbid psychiatric disorders and learning and memory impairments that seem to recover after a period of abstinence. Evidence regarding other cognitive domains and neurological consequences, including cerebrovascular events, is limited and inconsistent. Abstinence after treatment is only achieved in a minority of cases; treatment targeted at reduction in use appears have some success. Potential moderators of the impact of CUD on the brain include age of onset, heaviness of use, CUD severity, the ratio of ∆9-tetrahydrocannabinol to cannabidiol and severity of comorbid disorders.

CONCLUSIONS

Current evidence of long-term effects of daily cannabis use and cannabis use disorder on brain-related outcomes is suggestive rather than conclusive, but use is associated with psychiatric morbidity and with cognitive impairments that recover after a period of abstinence.

Effects of frequent marijuana use on risky decision-making in young adult college students

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Frequent marijuana users (MJ+) and controls completed the Iowa Gambling Task (IGT).

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MJ+ made significantly less advantageous decisions on the IGT relative to controls.

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Findings suggest frequent marijuana use may impair adaptive decision-making skills.

Marijuana (MJ) is the most widely used illicit substance among adolescents and young adults. Frequent MJ use has been associated with impairments in cognitive flexibility and inhibition, both of which play important roles in decision-making. However, the impact of frequent MJ use on decision-making performance is mixed and not well understood. The current study examined the influence of frequent MJ use on risky decision-making in college students, 18–22 years old. Methods: From 2017 to 2019, data was collected from young adult college students (n = 65) consisting of 32 healthy controls (HC) and 33 frequent marijuana users (MJ+). Participants completed the Iowa Gambling Task (IGT), a measure of risky decision-making, and net IGT scores (advantageous-disadvantageous decisions) were used as a measure of optimal decision-making. Results: The main finding indicated there was a significant effect of group on net IGT scores (p = 0.018), which remained significant when sex was included in the model (p = 0.006), such that MJ+ had lower net IGT scores than HC. Conclusions: These findings highlight potential differences in risky decision-making between MJ+ and HC, but it is uncertain whether these differences are pre-existing and increase vulnerability for frequent MJ use or if they are related to the effects of frequent MJ use on decision-making.

Working Memory and Response Inhibition Effects on At-Risk Youth's Willingness to Use Multiple Nicotine and Tobacco Products

Purpose: Past research has suggested that executive functions, such as working memory and response inhibition, predict the use of nicotine and tobacco products (NTPs). The current study extends prior research by assessing whether response inhibition and working memory are associated with at-risk youth's willingness to use NTPs. Methods: A sample of 1060 at-risk youth were recruited from alternative high schools in southern California. Participants were randomly assigned to complete the Symmetry Span Task, an indicator of working memory ability, or the cued Go/No-Go task, an indicator of response inhibition. Participants who reported never using NTPs (n = 348) indicated how willing they would be try NTPs. Results: Results from a cross-sectional zero-inflated negative binomial (ZINB) regression suggest that females with stronger working memory skills and individuals with weaker response inhibition skills were more likely to be unwilling to use NTPs. Conclusion: While further research is needed to determine whether executive functions can prospectively predict NTP use among at-risk youth, the current study indicates that both working memory and response inhibition may play a significant role.

Gambling and Cannabis Use: Clinical and Policy Implications

Eleven US States and the District of Columbia legally allow personal (i.e., recreational) cannabis use by adults, and an additional 22 states allow use of cannabis for medicinal purposes. Of these jurisdictions, only two do not have some form of legalized gambling available (https://www.casino.org/local/guide/). In contrast to this rapid increase in legally available marijuana is the limited knowledge about the intersection of cannabis use and gambling. This paper strives to define the current status of the relevant literatures and consider the implication for future gambling research. We describe the research literature on the prevalence of cannabis use and co-existing gambling problems and the effects of cannabis use on gambling-related cognitive functions and decision-making. We also discuss clinical considerations with treating problem gamblers with a cannabis use disorder. Finally, the potential implications for responsible gambling practices and policies and the most pressing gaps in the research literature are offered.

Cross-sectional analysis of cognitive function using multivariate normative comparisons in men with HIV disease

BACKGROUND

Prevalence estimates of cognitive impairment in HIV disease vary widely. Here we used multivariate normative comparison (MNC) with identify individuals with impaired cognition, and to compare the results with those using the Frascati and Gisslén criteria.

METHODS

The current project used data collected before October 2014 from bisexual/gay men from the Multicenter AIDS Cohort Study. A total of 2904 men (mean age 39.7 years, 52.7% seropositive) had complete data in six cognitive domains at their first neuropsychological evaluation. T-scores were computed for each domain and the MNC was applied to detect impairment among seronegative and seropositive groups.

RESULTS

The MNC classified 6.26% of seronegative men as being impaired using a predetermined 5% false discovery rate. By contrast, the Frascati and the Gisslén criteria identified 24.54 and 11.36% of seronegative men as impaired. For seropositive men, the percentage impairment was 7.45, 25.73, and 11.69%, respectively, by the MNC, Frascati and Gisslén criteria. When we used seronegative men without medical comorbidities as the control group, the MNC, the Frascati and the Gisslén criteria identified 5.05, 27.07, and 4.21% of the seronegative men, and 4.34, 30.95, and 4.48% of the seropositive men as having cognitive impairment. For each method, serostatus was not associated with cognitive impairment.

CONCLUSION

The MNC controls the false discovery rate and therefore avoids the low specificity that characterizes the Frascati and Gisslén criteria. More research is needed to evaluate the sensitivity of the MNC method in a seropositive population that may be sicker and older than the current study sample and that includes women.

EXTENDED ATTENUATION OF CORTICOSTRIATAL POWER AND COHERENCE AFTER ACUTE EXPOSURE TO VAPOURIZED Δ9 TETRAHYDROCANNABINOL IN RATS

Introduction

Over 14% of Canadians use cannabis, with nearly 60% of these individuals reporting daily or weekly use. Inhalation of cannabis vapour has recently gained popularity, but the effects of this exposure on neural activity remain unknown. In this study, we assessed the impact of acute exposure to vapourized Δ9-tetrahydrocannabinol (THC) on neural circuit dynamics in rats.

Objectives

We aimed to characterize the changes in neural activity in the dorsal striatum (dStr), orbitofrontal cortex (OFC), and prefrontal cortex (PFC), after acute exposure to THC vapour.

Methods

Rats were implanted with electrode arrays targeting the dStr, OFC, and PFC. Rats were administered THC (or vehicle) using a Volcano® vapourizer and local field potential recordings were performed in a plexiglass chamber in a cross-over design with a week-long washout period.

Results

Decreased spectral power was observed within the dStr, OFC, and PFC in the gamma range (>32-100 Hz) following vapourized THC administration. Most changes in gamma were still present 7 days after THC administration. Decreased gamma coherence was also observed between the OFC-PFC and dStr-PFC region-pairs.

Conclusion

A single exposure to vapourized THC suppresses cortical and dorsal striatal gamma power and coherence, effects that appear to last at least a week. Given the role of gamma hypofunction in schizophrenia, these findings may provide mechanistic insights into the known psychotomimetic effects of THC.

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.

Driving Under the Influence of Cannabis: A Framework for Future Policy

Marijuana is the most widely consumed illicit substance in the United States, and an increasing number of states have legalized it for both medicinal and recreational purposes. As it becomes more readily available, there will be a concurrent rise in the number of users and, consequently, the number of motor vehicle operators driving under the influence. This article examines the cognitive and psychomotor effects of cannabis, as well as current policy concerning driving under the influence of drugs. The authors performed a MEDLINE search on the epidemiology of cannabis use, its cognitive and psychomotor effects, and policies regarding driving under the influence of drugs. Twenty-eight epidemiological studies, 16 acute cognitive and psychomotor studies, 8 chronic cognitive and psychomotor studies, and pertinent state and federal laws and policies were reviewed. These search results revealed that marijuana use is associated with significant cognitive and psychomotor effects. In addition, the legalization of marijuana varies from state to state, as do the laws pertaining to driving under the influence of drugs. Marijuana is a commonly found illicit substance in motor vehicle operators driving under the influence of drugs. Current evidence shows that blood levels of tetrahydrocannabinol do not correlate well with the level of impairment. In addition, although acute infrequent use of cannabis typically leads to cognitive and psychomotor impairment, this is not consistently the case for chronic heavy use. To establish the framework for driving under the influence of cannabis policy, we must review the current published evidence and examine existing policy at state and federal levels.

Cream of the Crop: Clinical Representativeness of Eligible and Ineligible Cannabis Users in Research

BACKGROUND

Experts have recommended criteria (Gonzalez et al., 2002) for recruiting pure chronic cannabis users (i.e., those without polysubstance use or psychiatric illness) when evaluating cannabis' non-acute effects on cognition.

OBJECTIVES

We sought to demonstrate the implications of using such criteria by examining characteristics of respondents who completed an eligibility screening for a parent study evaluating the cognitive effects of chronic cannabis use.

METHODS

Over a 3-year, 8-month period, 612 respondents from the community completed an eligibility screening based on recommendations in the cannabis literature. Using independent samples t-tests and chi-square tests, we examined whether qualified/eligible respondents (n = 219) differed from non-qualified/ineligible respondents (n = 393).

RESULTS

Compared to ineligible cannabis users, eligible cannabis-using respondents were significantly younger, used cannabis more frequently, used alcohol less frequently, and were less likely to have a history of other drug use, a psychiatric diagnosis, or to have used psychiatric medication. Conclusions/Importance: Our findings indicate that eligible/pure cannabis users are not representative of typical cannabis users in the general community (i.e., ineligible users with polysubstance use and/or psychiatric diagnoses) who ultimately comprised the majority of our cannabis-using sample (65.2%). Thus, typical cannabis users may be more accurately characterized as polysubstance users, posing a number of challenges related to the generalizability of findings from studies utilizing pure samples of cannabis users. Recruiting samples of typical cannabis users will improve external validity in research. Furthermore, reporting comprehensive characteristics of such samples will enable consumers to gauge the applicability of study findings to populations of interest.

Perceptions of the cognitive effects of cannabis use: A survey of neuropsychologists' beliefs

Introduction: Research evaluating the neuropsychological effects of cannabis has yielded mixed findings, with some studies finding cognitive deficits in cannabis users (primarily in learning and memory) and others finding no significant effects. It is important to understand how clinicians perceive this discrepancy in the empirical literature. However, no studies have assessed neuropsychologists' beliefs regarding the effects of cannabis on cognitive functioning. Thus, this study sought to evaluate how patient and cannabis-use factors influence neuropsychologists' perceptions of cannabis's cognitive effects. Method: Neuropsychologists (N = 261) read eight vignettes, each depicting cannabis users varying in age, gender, and cannabis-use history (frequency, duration, and recreational/medicinal use). Respondents rated the anticipated effects of cannabis in each vignette on nine cognitive domains. Mixed effects linear regression modeled the ratings of cognitive abilities as a function of neuropsychologist, neuropsychologists' training, vignette, patient age, gender, and frequency/duration/type of cannabis use, and treated neuropsychologist and vignette as random effects. Results: Duration of use had the most notable effect on neuropsychologists' ratings, with a small (0.1 to 0.2 SDs) yet statistically significant (p < .001) negative effect on each cognitive domain. Male gender and medicinal use also predicted lower cognitive ratings. Differences in ratings between neuropsychologists accounted for 73% of the total variability in each domain, whereas variability due to vignette alone was negligible (<1%). Conclusions: Results suggest that neuropsychologists believe that cannabis use results in broad but mild cognitive deficits, consistent with meta-analytic findings of active chronic cannabis users, particularly for males and for individuals using cannabis for medicinal purposes. Interestingly, neuropsychologists expected fewer cognitive effects in recreational cannabis users. Further, duration of use (rather than frequency) was believed to be the primary factor contributing to cognitive deficits.

Association of Cannabis With Cognitive Functioning in Adolescents and Young Adults: A Systematic Review and Meta-analysis

IMPORTANCE

Substantial shifts in perception and policy regarding cannabis have recently occurred, with use of cannabis increasing while its perceived harm decreases. One possible risk of increased cannabis use is poorer cognitive functioning, especially in youth.

OBJECTIVE

To provide the first quantitative synthesis of the literature examining cannabis and cognitive functioning in adolescents and young adults (with a mean age of 26 years and younger).

DATA SOURCES

PubMed, PsycInfo, Academic Search Premier, Scopus, and bibliographies of relevant reviews were searched for peer-reviewed, English-language studies from the date the databases began through May 2017.

STUDY SELECTION

Consensus criteria were used to determine study inclusion through abstract and manuscript review.

DATA EXTRACTION AND SYNTHESIS

This study followed Meta-analysis of Observational Studies in Epidemiology guidelines. Effect size estimates were calculated using multivariate mixed-effects models for cognitive functioning outcomes classified into 10 domains.

MAIN OUTCOMES AND MEASURES

Results from neurocognitive tests administered in cross-sectional studies were primary outcomes, and we examined the influence of a priori explanatory variables on variability in effect size.

RESULTS

Sixty-nine studies of 2152 cannabis users (mean [SD] age, 20.6 [2.8] years; 1472 [68.4%] male) and 6575 comparison participants with minimal cannabis exposure were included (mean [SD] age, 20.8 [3.4]; 3669 [55.8%] male). Results indicated a small overall effect size (presented as mean d) for reduced cognitive functioning associated with frequent or heavy cannabis use (d, -0.25; 95% CI, -0.32 to -0.17; P < .001). The magnitude of effect sizes did not vary by sample age or age at cannabis use onset. However, studies requiring an abstinence period longer than 72 hours (15 studies; n = 928) had an overall effect size (d, -0.08; 95% CI, -0.22 to 0.07) that was not significantly different from 0 and smaller than studies with less stringent abstinence criteria (54 studies; n = 7799; d, -0.30; 95% CI, -0.37 to -0.22; P = .01).

CONCLUSIONS AND RELEVANCE

Associations between cannabis use and cognitive functioning in cross-sectional studies of adolescents and young adults are small and may be of questionable clinical importance for most individuals. Furthermore, abstinence of longer than 72 hours diminishes cognitive deficits associated with cannabis use. Although other outcomes (eg, psychosis) were not examined in the included studies, results indicate that previous studies of cannabis in youth may have overstated the magnitude and persistence of cognitive deficits associated with use. Reported deficits may reflect residual effects from acute use or withdrawal. Future studies should examine individual differences in susceptibility to cannabis-associated cognitive dysfunction.

Early Cannabis Use and Neurocognitive Risk: A Prospective Functional Neuroimaging Study

BACKGROUND

Retrospective neuroimaging studies have suggested an association between early cannabis onset and later neurocognitive impairment. However, these studies have been limited in their ability to distinguish substance use risk factors from cannabis-induced effects on neurocognition. We used a prospective cohort design to test whether neurocognitive differences preceded cannabis onset (substance use risk model) and if early cannabis use was associated with poorer neurocognitive development (cannabis exposure model).

METHODS

Participants (N = 85) completed a visuospatial working memory task during functional magnetic resonance imaging and multiple cognitive assessments (Wechsler Intelligence Scale for Children-IV, Cambridge Neuropsychological Test Automated Battery) at 12 years of age, before any reported cannabis use (baseline), and at 15 years of age (follow-up: N = 85 cognitive assessments, n = 67 neuroimaging). By follow-up, 22 participants reported using cannabis and/or failed a Δ⁹-tetrahydrocannabinol urine screen (users).

RESULTS

At baseline, group differences supported a risk model. Those who would initiate cannabis use by 15 years of age had activation differences in frontoparietal (increased) and visual association (decreased) regions and poorer executive planning scores (Stockings of Cambridge) compared with noninitiators. Limited support was found for a cannabis exposure model. At follow-up, activation in the cuneus displayed a significant cannabis dose-response relationship, although neither cannabis dose nor cuneus activation was associated with cognitive performance.

CONCLUSIONS

The purported neurocognitive effects of early cannabis onset may not be due to cannabis initiation alone but also driven by limitations or late development of neurocognitive systems predictive of substance use. In addition, more prolonged cannabis exposure may be required to observe the cognitive effects of early cannabis onset.

Maltreatment, Coping, and Substance Use in Youth in Foster Care: Examination of Moderation Models

Child maltreatment is associated with negative outcomes such as substance use (SU). This study tested relations among maltreatment history, coping behavior, and SU behavior in youth residing in foster care. Participants were 210 youth ( M_age = 12.71 years; SD = 2.95) in foster care who completed self-report measures through an audio computer-assisted self-interview program. Using a structural equation modeling framework and latent measurement constructs, positive associations were identified between maltreatment at baseline and coping behavior outcomes as well as SU behavior outcome approximately 4.5 months later. Specifically, greater severity and chronicity of maltreatment was associated with greater SU behavior as well as indirect action, prosocial, and asocial coping behavior. Maltreatment was not significantly related to direct action coping behavior. In moderation tests, only asocial coping provided a significant interaction effect for SU behavior outcomes; SU behavior did not moderate pathways between maltreatment and coping behavior. For youth in foster care, the coping approach may be varied and relate differentially to SU behavior outcomes, with asocial approaches to coping acting as a buffer for the maltreatment/SU relation. Additionally, SU remains an important target for intervention and prevention in youth residing in foster care.

The effect of interactions between genetics and cannabis use on neurocognition. A review

BACKGROUND

Cannabis is one of the most widely-used drugs in industrialized countries. It is now well established that cannabis use impacts neurocognition. In the intoxication period time episodic memory, working memory and attention are impacted and impulsivity is increased. The long-term effects of cannabis use tend to be similar. Various internal factors, such as sex differences, modulate this impact. It is unclear whether genetic variations can also influence the impact of cannabis on neurocognition. We set out to examine the impact of genetic variations on neurocognition in cannabis users.

METHOD

We conducted a search via the PubMed, Web of Science, and ScienceDirect databases to identify studies measuring neurocognition and assessing genotypes in the context of cannabis use.

RESULTS

We included 13 articles. We found that working memory, verbal and visual memory and sustained attention are more impacted during intoxication in subjects with the Val COMT allele. COMT gene could also modulate sustained attention in regular use. The CNR1, AKT1, DBH and 5-HTT/SLC6A4 genes may also modulate effects.

CONCLUSION

Most of these genes are linked to schizophrenia. A fuller understanding of their impact on the effects of cannabis on neurocognition would thus help elucidate the mechanisms linking cannabis and psychosis. However, evidence is still scant, and more research is needed.

The effects of cannabis use on salience attribution: a systematic review

OBJECTIVE

The relationship between cannabis use and the onset of psychosis is well established. Aberrant salience processing is widely thought to underpin many of these symptoms. Literature explicitly investigating the relationship between aberrant salience processing and cannabis use is scarce; with those few studies finding that acute tetrahydrocannabinol (THC) administration (the main psychoactive component of cannabis) can result in abnormal salience processing in healthy cohorts, mirroring that observed in psychosis. Nevertheless, the extent of and mechanisms through which cannabis has a modulatory effect on aberrant salience, following both acute and chronic use, remain unclear.

METHODS

Here, we systematically review recent findings on the effects of cannabis use - either through acute THC administration or in chronic users - on brain regions associated with salience processing (through functional MRI data); and performance in cognitive tasks that could be used as either direct or indirect measures of salience processing. We identified 13 studies either directly or indirectly exploring salience processing. Three types of salience were identified and discussed - incentive/motivational, emotional/affective, and attentional salience.

RESULTS

The results demonstrated an impairment of immediate salience processing, following acute THC administration. Amongst the long-term cannabis users, normal salience performance appeared to be underpinned by abnormal neural processes.

CONCLUSIONS

Overall, the lack of research specifically exploring the effects of cannabis use on salience processing, weaken any conclusions drawn. Additional research explicitly focussed on salience processing and cannabis use is required to advance our understanding of the neurocognitive mechanisms underlying the association between cannabis use and development of psychosis.

Involvement of cannabinoid system in the nucleus accumbens on delay-based decision making in the rat

The nucleus accumbens (NAc) plays a fundamental role in decision making and anticipation of reward. In addition, exogenous cannabinoids affect the behavior of humans and animals including disruption of short-term memory and cognitive impairments. Therefore, in this study, cannabinoid agonist and antagonist were administrated into the NAc to determine the effect of cannabinoid activation in the entire NAc on delay-based decision making. Rats were trained on a cost-benefit T-maze decision making task in which the animals were well-trained to choose between a small/immediate reward and a large/delay reward. After training, the animals were implanted with guide cannulae in the NAc. On test day, they received cannabinoid agonist (Win 55,212-2; 10, 50 and 100μM) and/or antagonist (AM251; 45μM) into the NAc. Percentage of high reward choice and latency of reward achievement were evaluated. Results showed that cannabinoid agonist administration caused a decrease in high reward choice such that rats selected small/immediate reward instead of large/delay reward. Moreover, in agonist-treated animals latency of reward achievement increased. Effects of cannabinoid activation on delay-based decision making with equivalent delays demonstrated that if the delay was equated on both arm goals, animals still had a preference for the high/delay reward, showing the results was not caused by an impairment of spatial preference or memory. These finding clarified that cannabinoid system activation in the entire NAc plays a critical role in the regulation of delay-based decision making.

Cognitive Function of Children and Adolescents with Attention-Deficit/Hyperactivity Disorder in a 2-Year Open-Label Study of Lisdexamfetamine Dimesylate

BACKGROUND

SPD489-404 was the first 2-year safety study of lisdexamfetamine dimesylate in the treatment of attention-deficit/hyperactivity disorder in children and adolescents. In accordance with advice from the European Medicines Agency, assessment of cognitive function was a predefined safety outcome in SPD489-404.

OBJECTIVE

The objective of this study was to assess cognitive function over 2 years in study SPD489-404, using the Cambridge Neuropsychological Test Automated Battery (CANTAB).

METHODS

Participants aged 6-17 years received dose-optimised open-label lisdexamfetamine dimesylate (30, 50 or 70 mg/day) for 104 weeks. Cognition was assessed using four CANTAB tasks; Delayed Matching to Sample (DMS), Spatial Working Memory (SWM), Stop Signal Task (SST) and Reaction Time (RTI). Key and additional variables were pre-specified for each CANTAB task; groupwise mean percentage changes in key variables from baseline of > 5% were considered potentially clinically significant.

RESULTS

All 314 enrolled participants received lisdexamfetamine dimesylate and were included in the safety population, and 191 (60.8%) completed the study. No potentially clinically significant deteriorations from baseline were observed in any key CANTAB variable over the 2 years of the study. Based on predefined thresholds, potentially clinically significant improvements from baseline were observed at 6 months (DMS median reaction time, mean per cent change, - 6.6%; SWM total between-search errors, - 22.8%; SST stop signal reaction time, -18.9%), and at the last on-treatment assessment (DMS median reaction time, - 6.5%; SWM total between-search errors, - 32.6%; SST stop signal reaction time, - 25.7%).

CONCLUSIONS

Lisdexamfetamine dimesylate treatment for 2 years was not associated with deterioration of cognitive function in children and adolescents with attention-deficit/hyperactivity disorder. Although improvements in some cognitive measures were observed, lack of a control group makes interpretation of the findings difficult. Further studies of the impact of stimulants on cognition are required. CLINICALTRIALS.

GOV IDENTIFIER

NCT01328756.

Adolescent cannabis use, change in neurocognitive function, and high-school graduation: A longitudinal study from early adolescence to young adulthood

The main objective of this prospective longitudinal study was to investigate bidirectional associations between adolescent cannabis use (CU) and neurocognitive performance in a community sample of 294 young men from ages 13 to 20 years. The results showed that in early adolescence, and prior to initiation to CU, poor short-term and working memory, but high verbal IQ, were associated with earlier age of onset of CU. In turn, age of CU onset and CU frequency across adolescence were associated with (a) specific neurocognitive decline in verbal IQ and executive function tasks tapping trial and error learning and reward processing by early adulthood and (b) lower rates of high-school graduation. The association between CU onset and change in neurocognitive function, however, was found to be accounted for by CU frequency. Whereas the link between CU frequency across adolescence and change in verbal IQ was explained (mediated) by high school graduation, the link between CU frequency and tasks tapping trial and error learning were independent from high school graduation, concurrent cannabis and other substance use, adolescent alcohol use, and externalizing behaviors. Findings support prevention efforts aimed at delaying onset and reducing frequency of CU.

Age and impulsive behavior in drug addiction: A review of past research and future directions

Impulsive behavior is implicated in the initiation, maintenance, and relapse of drug-seeking behaviors involved in drug addiction. Research shows that changes in impulsive behavior across the lifespan contribute to drug use and addiction. The goal of this review is to examine existing research on the relationship between impulsive behavior and drug use across the lifespan and to recommend directions for future research. Three domains of impulsive behavior are explored in this review: impulsive behavior-related personality traits, delay discounting, and prepotent response inhibition. First, we present previous research on these three domains of impulsive behavior and drug use across developmental stages. Then, we discuss how changes in impulsive behavior across the lifespan are implicated in the progression of drug use and addiction. Finally, we discuss the relatively limited attention given to middle-to-older adults in the current literature, consider the validity of the measures used to assess impulsive behavior in middle-to-older adulthood, and suggest recommendations for future research.

Effect of ageing on neurocognitive function by stage of HIV infection: evidence from the Multicenter AIDS Cohort Study

BACKGROUND

The demographics of the HIV epidemic in the USA have shifted towards older age. We aimed to establish the relationship between the processes of ageing and HIV infection in neurocognitive impairment.

METHODS

With longitudinal data from the Multicenter AIDS Cohort Study, a long-term prospective cohort study of the natural and treated history of HIV infection among men who have sex with men in the USA, we examined the effect of ageing, HIV infection (by disease stage), and their interaction on five neurocognitive domains: information processing speed, executive function, episodic memory, working memory, and motor function. We controlled for duration of serostatus in a subanalysis, as well as comorbidities and other factors that affect cognition. Analyses were by linear mixed models for longitudinal data.

FINDINGS

5086 participants (47 886 visits) were included in the analytic sample (2278 HIV-seropositive participants contributed 20 477 visits and 2808 HIV-seronegative control participants contributed 27 409 visits). In an a-priori multivariate analysis with control variables including comorbidities and time since seroconversion, significant, direct negative effects of ageing were noted on all neurocognitive domains (p<0·0001 for all). Similar effects were noted for late-stage HIV disease progression on information processing speed (p=0·002), executive function (p<0·0001), motor function (p<0·0001), and working memory (p=0·001). Deleterious interaction effects were also noted in the domains of episodic memory (p=0·03) and motor function (p=0·02).

INTERPRETATION

A greater than expected effect of ageing on episodic memory and motor function with advanced stages of HIV infection suggests that these two domains are most susceptible to the progression of neurocognitive impairment caused by ageing in individuals with HIV. This deficit pattern suggests differential damage to the hippocampus and basal ganglia (specifically nigrostriatal pathways). Older individuals with HIV infection should be targeted for regular screening for HIV-associate neurocognitive disorder, particularly with tests referable to the episodic memory and motor domains.

FUNDING

National Institute of Mental Health.

Marijuana use and physical dating violence among adolescents and emerging adults: A systematic review and meta-analysis

BACKGROUND

As restrictions on marijuana are loosened, there is concern of a coming increase in marijuana use among adolescents and emerging adults, which could be coupled with commensurate increases in behavioral problems associated with use, such as physical dating violence (PDV). To summarize what is known about the association between marijuana use and PDV victimization and perpetration among 11-21year olds, we conducted a systematic review and meta-analysis of the relevant literature published between 2003 and 2015.

METHODS

Candidate articles were identified with a systematic search, and we used inclusion and exclusion criteria to review titles, abstracts, and the full text of studies for consideration. There were 13 articles examining marijuana in association with PDV; five addressed victimization and 11 addressed perpetration.

RESULTS

Findings suggest that marijuana use is associated with a 54% increase in the odds PDV victimization, and a 45% increase in the odds of perpetration.

CONCLUSIONS

Findings suggest that dating violence is a correlate of marijuana use, and that association is strongest among adolescents (vs. emerging adults) and girls (vs. boys). Therefore, it should be routinely included as a core data item in marijuana surveillance systems, so as to allow for behavioral monitoring.

Cognitive motor deficits in cannabis users

Cannabis use affects cortico-striatal networks that are essential for producing movement. In this review, we summarize the literature on motor system dysfunction in cannabis users and provide a rationale for why motor learning should be considered an important area in cannabis research. A majority of studies have addressed cognitive impairments in cannabis users and some have focused on driving performance, motor impulsivity, and motor inhibition. Our review of the literature has found that cannabis use is associated with motor performance impairments; however, there is a gap in the literature regarding impairments in motor learning. The involvement of the cortico-striatal network in both cannabis addiction and movement also suggests potential avenues for treatment and rehabilitation via the motor system.