Longitudinal study of cognition among adolescent marijuana users over three weeks of abstinence

Cannabinoid CB1 receptor-sensitive neurodevelopmental processes and trajectories

As high-potency cannabis (with high Δ9-Tetrahydrocannabinol content) becomes easily accessible and widespread, it is of extreme importance for public health that a scientific platform is used to implement practical guidelines, particularly for at-risk populations. Many reviews have been written in the past decade summarizing the impact of cannabis in the developing brain. One critical concept frequently mentioned but not discussed in detail is whether there are sensitive neurodevelopmental events driving the age-specific sensitivity to cannabis, particularly those mediated by cannabinoid type 1 receptor signaling. By integrating available data from humans and animal models, the goal of the present expert review article is to provide a mechanistic overview on how cannabis exposure during sensitive periods of neural circuit plasticity and development can result in lasting consequences. Here we used the frontal cortex as a proxy to align the trajectory of the brain cannabinoid system between humans and rodents. Both the strengths and limitations of available mechanistic studies on the effects of cannabis and cannabinoids were discussed using a developmental framework from which neural circuit adaptations during sensitive periods are considered. Such an approach is needed to align key neurodevelopmental variables through the lifespan, which in turn will provide valuable insights applicable to the human brain by defining the underpinning mechanisms of sensitive periods and how the impact of cannabis changes from childhood to adolescence, and thereafter through young adulthood.

Young Age and Concomitant Cannabis (THC) and Ethanol (EtOH) Exposure Enhances Rat Brain Damage Through Decreased Cerebral Mitochondrial Respiration

The reason why young people taking concomitantly cannabis (THC) and ethanol (EtOH) are more prone to stroke is underresearched. To investigate whether an underlying mechanism of increased brain damage could be an impaired mitochondrial function, this experiment determined the acute effects of EtOH, both alone and associated with THC, on mitochondrial respiration and oxidative stress (hydrogen peroxide H2O2) on young (11 weeks) and middle-aged (45 weeks) brain in rats, using a high-resolution oxygraph (Oxygraph-2K, Oroboros instruments). In young brains, EtOH decreased mitochondrial respiration by -51.76 ± 2.60% (from 32.76 ± 3.82 to 17.41 ± 1.42 pmol/s/mL, p < 0.0001). In 45-week-old brains, the decrease was lesser, but still significant -36.0 ± 2.80% (from 30.73 ± 7.72 to 20.59 ± 5.48 pmol/s/mL, p < 0.0001). Concomitant THC aggravated brain mitochondrial respiration decreases at 11 weeks (-86.86 ± 1.74%, p < 0.0001) and at 45 weeks (-73.95 ± 3.69%, p < 0.0001). Such additional injury was enhanced in young brains (p < 0.01). H2O2 production was similar in both age groups (1.0 ± 0.2 versus 1.1 ± 0.08 pmol O2/s/mL) and was not modified by THC addition. In conclusion, EtOH alone significantly impairs brain mitochondrial respiration and concomitant THC further aggravates such damage, particularly in young brains. These data support the hypothesis that enhanced mitochondrial dysfunction might participate in the increased occurrence of stroke in the young and urge for better prevention against EtOH and THC addictions in adolescents.

Spatial Craving Patterns in Marijuana Users: Insights From fMRI Brain Connectivity Analysis With High-Order Graph Attention Neural Networks

The excessive consumption of marijuana can induce substantial psychological and social consequences. In this investigation, we propose an elucidative framework termed high-order graph attention neural networks (HOGANN) for the classification of Marijuana addiction, coupled with an analysis of localized brain network communities exhibiting abnormal activities among chronic marijuana users. HOGANN integrates dynamic intrinsic functional brain networks, estimated from functional magnetic resonance imaging (fMRI), using graph attention-based long short-term memory (GAT-LSTM) to capture temporal network dynamics. We employ a high-order attention module for information fusion and message passing among neighboring nodes, enhancing the network community analysis. Our model is validated across two distinct data cohorts, yielding substantially higher classification accuracy than benchmark algorithms. Furthermore, we discern the most pertinent subnetworks and cognitive regions affected by persistent marijuana consumption, indicating adverse effects on functional brain networks, particularly within the dorsal attention and frontoparietal networks. Intriguingly, our model demonstrates superior performance in cohorts exhibiting prolonged dependence, implying that prolonged marijuana usage induces more pronounced alterations in brain networks. The model proficiently identifies craving brain maps, thereby delineating critical brain regions for analysis.

Brain Function and Marijuana: Are there Changes after Abstinence of Consumption? Preliminary Results

BACKGROUND

The legalization of cannabis use and false claims about the plant Cannabis sativa to be considered a pharmaceutical product have been found to increase consumption, lower risk perception, and lead to more health problems, without reducing criminal activity. Brain function, typically assessed by neuropsychological tests, shows abnormalities with acute marijuana use, but inconsistent results have been published after abstinence, with a maximum follow-up of 28 days. Our previous research, using neuropsychological tests and brain perfusion single photon emission computed tomography (neuroSPECT), demonstrated consistent abnormalities in brain function among schoolchildren who consume marijuana compared to their non-consuming peers. The aim of this study is to investigate whether brain function changes in 20 adult marijuana users after 6 months of abstinence.

METHODOLOGY

Comparison of neuropsychological tests (Rey Complex Figure; Porteus Maze; Four subtests of WAIS-IV Intellectual Tests; STROOP; D2) and perfusion neuroSPECT (functional images), obtained in relation to recent consumption and after 6 months of serial drug-screening test confirmed abstinence.

RESULTS

In a one-year period (2020-2021) only five compliant participants were recruited. The COVID-19 pandemic was a limiting factor. Preliminary results of neuropsychological tests, functional brain perfusion images and limited statistical analysis are presented. The results of the neuropsychological tests of the three subjects who completed the abstinence period so far show some improvement in working memory and attention after abstinence. NeuroSPECT shows disorganized hypoperfusion of variable severity in relation to recent consumption, involving areas associated with cognitive function such as the posterior cingulate and temporal lobes, in our five initially enrolled patients, when compared to a normal database. Of these, only two participants have already been re-evaluated with neuroSPECT after 6 months of abstinence, one of whom showed some improvement on the post-abstinence images.

CONCLUSION

We analyze the methodological challenges of this research, including the pandemic, to incorporate the appropriate corrections in the next phase of our investigation. Our final findings may provide clinicians and users with information about the long-term effects of marijuana use on brain function.

A systematic review of evidence on integrated management of psychiatric disorders in youth who use cannabis

Given the risks to mental health associated with cannabis use in youth and the increase in cannabis legalization worldwide and in the U.S., there is a need to understand existing evidence-based approaches to integrated management of psychiatric disorders in youth who use cannabis. This systematic review aimed to appraise the current evidence on integrated treatment for adolescents and young adults with common psychiatric disorders who engage in regular cannabis use. A total of 989 studies were screened for inclusion. Study's titles and abstracts were screened and advanced to full text review for further screening by two independent reviewers. Thirty-five full-text articles were reviewed, with five articles ultimately meeting all criteria for inclusion. Five randomized controlled trials examined the effects of therapeutic interventions in youth with common psychiatric disorders who used cannabis, including two studies on depression, one on bipolar disorder, one on anxiety and one on PTSD were reviewed. No studies were considered high in risk of bias. Overall, there is a paucity of research on the treatment of comorbid adolescent mental health disorders and cannabis use, which limits the ability to draw evidence-based treatment recommendations.

Cannabis use and neurocognitive performance at 13-14 Years-Old: Optimizing assessment with hair toxicology in the Adolescent brain cognitive development (ABCD) study

OBJECTIVE

Cannabis is widely used, including in early adolescence, with prevalence rates varying by measurement method (e.g., toxicology vs. self-report). Critical neurocognitive development occurs throughout adolescence. Given conflicting prior brain-behavior results in cannabis research, improved measurement of cannabis use in younger adolescents is needed.

METHODS

Data from the Adolescent Brain Cognitive Development (ABCD) Study Year 4 follow-up (participant age: 13-14 years-old) included hair samples assessed by LC-MS/MS and GC-MS/MS, quantifying THCCOOH (THC metabolite), THC, and cannabidiol concentrations, and the NIH Toolbox Cognitive Battery. Youth whose hair was positive for cannabinoids or reported past-year cannabis use were included in a Cannabis Use (CU) group (n = 123) and matched with non-using Controls on sociodemographics (n = 123). Standard and nested ANCOVAs assessed group status predicting cognitive performance, controlling for family relationships. Follow-up correlations assessed cannabinoid hair concentration, self-reported cannabis use, and neurocognition.

RESULTS

CU scored lower on Picture Memory (p = .03) than Controls. Within the CU group, THCCOOH negatively correlated with Picture Vocabulary (r = -0.20, p = .03) and Flanker Inhibitory Control and Attention (r = -0.19, p = .04), and past-year cannabis use was negatively associated with List Sorting Working Memory (r = -0.33, p = .0002) and Picture Sequence Memory (r = -0.19, p = .04) performances.

CONCLUSIONS

Youth who had used cannabis showed lower scores on an episodic memory task, and more cannabis use was linked to poorer performances on verbal, inhibitory, working memory, and episodic memory tasks. Combining hair toxicology with self-report revealed more brain-behavior relationships than self-report data alone. These youth will be followed to determine long-term substance use and neurocognition trajectories.

[Cannabis use in adolescents : Narrative Review and Position paper of the "Addiction Disorders in Adolescents" task force of the Austrian Society for Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy (ÖGKJP)]

BACKGROUND

Cannabis is the illegal drug most frequently used by Minors in Austria. Due to the gradual decriminalization and legalization that has taken place in many European countries in recent years, the ÖGKJP would like to take a balanced and scientifically based stand on the complex issue of cannabis use and abuse among young people.

METHODS

The authors searched the medline for current studies using searches tailored to each specific subtopic. Furthermore, recognized compendiums were quoted.

RESULTS

While occasional recreational use of cannabis in adults with completed brain maturation and no risk profile for mental disorders is likely to be relatively harmless, early initiation of use with regular use and the increasingly available, highly potent cannabis varieties can lead to explicit and sometimes irreversible neurocognitive brain dysfunction.

CONCLUSION

Legalisation of cannabis consumption for minors needs to be objected to due to the risks of the expected damage in the area of brain development. At the same time, however, it is important to establish sensible legal regulations in order to be able to adequately counteract the fact that over 30% of all European young people occasionally consume cannabis. We are also clearly recommending to not criminalize cannabis users and provide necessary support to vulnerable and addicted cannabis users.

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.

Towards a New Dynamic Interaction Model of Adolescent CUD Manifestation, Prevention, and Treatment: A Narrative Review

Background

Cannabis is one of the most popular drugs of the 21st century, especially among adolescents and young adults. Evidence of a variety of lasting neuropsychological deficits as a result of chronic cannabis use has increased. Furthermore, regular cannabis use is found to be a predictor of mental health problems, less motivation in school, and school dropout.

Aim

Our goal is to propose a theoretical model of adolescent cannabis use disorder (CUD) based on Zinberg's drug, set, and setting model and explicated by a review of the literature on adolescent cannabis use to improve the prevention and treatment of CUD for adolescents.

Methods

PubMed and Web of Science were searched for relevant publications as part of a hypothesis-based and model-generating review.

Results

Individual (set) and environmental (setting) risk factors play important roles in the development of CUD in adolescents. School performance, motivation, and attendance can be negatively influenced by persistent cannabis use patterns and adolescent brain development can consequently be impaired. Thus, cannabis use can be understood as both being the cause of poor school performance but also the consequence of poor school performance. To prevent and reduce adolescent CUD the drug, set, and setting must all be considered. It is important to notice that the multiple feedback loops (indicated in our dynamic interaction model) are not mutually exclusive, but offer important intervention focus points for social workers, addiction professionals, parents, and other care takers.

Conclusion

We argue that the three dimensions of drug, set, and setting contribute significantly to the eventual manifestation of CUD. Based on our dynamic interaction model, recommendations are made for possible preventive and therapeutic interventions for the treatment of adolescents and young adults with CUD.

Effects of combined use of alcohol and delta-9-tetrahydrocannibinol on working memory in Long Evans rats

The increase in social acceptance and legalization of cannabis over the last several years is likely to increase the prevalence of its co-use with alcohol. In spite of this, the potential for effects unique to co-use of these drugs, especially in moderate doses, has been studied relatively infrequently. We addressed this in the current study using a laboratory rat model of voluntary drug intake. Periadolescent male and female Long-Evans rats were allowed to orally self-administer ethanol, Δ9-tetrahydrocannibinol (THC), both drugs, or their vehicle controls from postnatal day (P) 30 to P47. They were subsequently trained and tested on an instrumental behavior task that assesses attention, working memory and behavioral flexibility. Similar to previous work, consumption of THC reduced both ethanol and saccharin intake in both sexes. Blood samples taken 14 h following the final self-administration session revealed that females had higher levels of the THC metabolite THC-COOH. There were modest effects of THC on our delayed matching to position (DMTP) task, with females exhibiting reduced performance compared to their control group or male, drug using counterparts. However, there were no significant effects of co-use of ethanol or THC on DMTP performance, and drug effects were also not apparent in the reversal learning phase of the task when non-matching to position was required as the correct response. These findings are consistent with other published studies in rodent models showing that use of these drugs in low to moderate doses does not significantly impact memory or behavioral flexibility following a protracted abstinence period.

[Analysis of the psychological causes of early substance use among adolescents in school and university settings]

Experimentation with psychoactive substances (PAS), such as alcohol, tobacco or cannabis, is common in adolescence, and continues to pose a public health issue that can lead to failure at school and university. Most of the work on these issues focuses on addiction-related aspects, and little on the underlying causes of addiction. This article sheds psycho-social theoretical light on the causes of first-time use of APS, and cannabis in particular. It is particularly aimed at school nurses and university preventive medicine nurses.

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.

Effects of combined use of alcohol and delta-9-tetrahydrocannibinol on working memory in Long Evans rats

The increase in social acceptance and legalization of cannabis over the last several years is likely to increase the prevalence of its co-use with alcohol. In spite of this, the potential for effects unique to co-use of these drugs, especially in moderate doses, has been studied relatively infrequently. We addressed this in the current study using a laboratory rat model of voluntary drug intake. Periadolescent male and female Long-Evans rats were allowed to orally self-administer ethanol, Î" 9 -tetrahydrocannibinol (THC), both drugs, or their vehicle controls from postnatal day (P) 30 to P47. They were subsequently trained and tested on an instrumental behavior task that assesses attention, working memory and behavioral flexibility. Similar to previous work, consumption of THC reduced both ethanol and saccharin intake in both sexes. Blood samples taken 14h following the final self-administration session revealed that females had higher levels of the THC metabolite THC-COOH. There were modest effects of THC on our delayed matching to position (DMTP) task, with females exhibiting reduced performance compared to their control group or male, drug using counterparts. However, there were no significant effects of co-use of ethanol or THC on DMTP performance, and drug effects were also not apparent in the reversal learning phase of the task when non-matching to position was required as the correct response. These findings are consistent with other published studies in rodent models showing that use of these drugs in low to moderate doses does not significantly impact memory or behavioral flexibility following a protracted abstinence period.

Regular recreational Cannabis users exhibit altered neural oscillatory dynamics during attention reorientation

BACKGROUND

Cannabis is the most widely used illicit drug in the United States and is often associated with changes in attention function, which may ultimately impact numerous other cognitive faculties (e.g. memory, executive function). Importantly, despite the increasing rates of cannabis use and widespread legalization in the United States, the neural mechanisms underlying attentional dysfunction in chronic users are poorly understood.

METHODS

We used magnetoencephalography (MEG) and a modified Posner cueing task in 21 regular cannabis users and 32 demographically matched non-user controls. MEG data were imaged in the time-frequency domain using a beamformer and peak voxel time series were extracted to quantify the oscillatory dynamics underlying use-related aberrations in attentional reorienting, as well as the impact on spontaneous neural activity immediately preceding stimulus onset.

RESULTS

Behavioral performance on the task (e.g. reaction time) was similar between regular cannabis users and non-user controls. However, the neural data indicated robust theta-band synchronizations across a distributed network during attentional reorienting, with activity in the bilateral inferior frontal gyri being markedly stronger in users relative to controls (p's < 0.036). Additionally, we observed significantly reduced spontaneous theta activity across this distributed network during the pre-stimulus baseline in cannabis users relative to controls (p's < 0.020).

CONCLUSIONS

Despite similar performance on the task, we observed specific alterations in the neural dynamics serving attentional reorienting in regular cannabis users compared to controls. These data suggest that regular cannabis users may employ compensatory processing in the prefrontal cortices to efficiently reorient their attention relative to non-user controls.

Investigating the "two-hit hypothesis": Effects of prenatal maternal immune activation and adolescent cannabis use on neurodevelopment in mice

Prenatal exposure to maternal immune activation (MIA) and chronic adolescent cannabis use are both risk factors for neuropsychiatric disorders. However, exposure to a single risk factor may not result in major mental illness, indicating that multiple exposures may be required for illness onset. Here, we examine whether combined exposure to prenatal MIA and adolescent delta-9-tetrahydrocannabinol (THC), the main psychoactive component of cannabis, lead to enduring neuroanatomical and behavioural changes in adulthood. Mice were prenatally exposed to viral mimetic, poly I:C (5 mg/kg), or vehicle at gestational day (GD) 9, and postnatally exposed to chronic THC (5 mg/kg, intraperitoneal) or vehicle during adolescence (postnatal day [PND]28-45). Longitudinal magnetic resonance imaging (MRI) was performed pre-treatment, PND 25, post-treatment, PND 50, and in adulthood, PND85, followed by behavioural tests for anxiety-like, social, and sensorimotor gating. Post-mortem assessment of cannabinoid (CB)1 and 2 receptor expressing cells was performed in altered regions identified by MRI (anterior cingulate and somatosensory cortices, striatum, and hippocampus). Subtle deviations in neurodevelopmental trajectory and subthreshold anxiety-like behaviours were observed in mice exposed to both risk factors. Sex-dependent effects were observed in patterns of shared brain-behaviour covariation, indicative of potential sex differences in response to MIA and THC. Density of CB1 and CB2 receptor positive cells was significantly decreased in all mice exposed to MIA, THC, or both. These findings suggest that there may be a cumulative effect of risk factor exposure on gross neuroanatomical development, and that the endocannabinoid system may be sensitive to both prenatal MIA, adolescent THC, or the combination.

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.

Substance abuse and susceptibility to false memory formation: a systematic review and meta-analysis

Background

Substance abuse has an impact on various cognitive domains, including memory. Even though this impact has been extensively examined across different subdomains, false memory has been sparsely studied. This systematic review and meta-analysis seek to synthesize the current scientific data concerning false memory formation in individuals with a history of substance abuse.

Methods

PubMed, Scopus, the Cochrane Library, Web of Science, and PsycINFO were searched to identify all experimental and observational studies in English, Portuguese, and Spanish. Studies were then examined by four independent reviewers and, if they met the inclusion criteria, assessed for their quality. The Cochrane Risk of Bias Tool for randomized controlled trials (RCT) and the Joanna Briggs Institute (JBI) critical appraisal checklists for quasi-experimental and analytic cross-sectional studies were used to assess the risk of bias.

Results

From the 443 screened studies, 27 (and two more from other sources) were considered eligible for full-text review. A final 18 studies were included in the present review. Of these, 10 were conducted with alcoholics or heavy drinkers, four focused on ecstasy/polydrug users, three were done with cannabis users and one focused on methadone maintenance patients with current cocaine dependence. Regarding false memory type, 15 studies focused on false recognition/recall, and three on provoked confabulation.

Conclusions

None but one of the studies considering false recognition/recall of critical lures found any significant differences between individuals with a history of substance abuse and healthy controls. However, most of the studies taking into account false recognition/recall of related and unrelated events found that individuals with a history of substance abuse showed significantly higher rates of false memories than controls. Future research should continue to consider different types of false memories as well as their potential association with relevant clinical variables.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=266503, identifier: CRD42021266503.

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.

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.

Assessment of Withdrawal, Mood, and Sleep Inventories After Monitored 3-Week Abstinence in Cannabis-Using Adolescents and Young Adults

Introduction: Among adolescents and young adults, cannabis use is prevalent. Prior studies characterizing withdrawal effects in this age range have primarily included treatment seeking or comorbid psychiatric samples; these studies have identified several affected domains, especially sleep, mood, and anxiety. The present study compared a community (i.e., nontreatment seeking) sample of cannabis-using and control participants on mood, anxiety, sleep, and withdrawal inventories during the course of a monitored 3-week cannabis abstinence period. Materials and Methods: Seventy-nine adolescent and young adult participants (cannabis-using group=37 and control group=42) were recruited from the community to undergo 3 weeks of confirmed abstinence (i.e., urine and sweat patch toxicology) and completion of Cannabis Withdrawal Symptom Criteria, State-Trait Anxiety Inventory, Beck's Depression Inventory, and Pittsburgh Sleep Quality Index across the study period. Repeated measures and cross-sectional regressions were used to examine main effects of group and interactions with time (where appropriate), while accounting for recent alcohol use and cotinine levels. Results: Cannabis-using participants reported higher mood (p=0.006), overall withdrawal (p=0.009), and sleep-related withdrawal (p<0.001) symptoms across abstinence compared to controls. Overall withdrawal severity (p=0.04) and sleep-related withdrawal symptoms (p=0.02) demonstrated a quadratic trajectory across the monitored abstinence periods, with an increase from baseline and subsequent decreases in symptom severity. No differences of anxiety scores (p=0.07) or trajectories (p=0.18) were observed. By study completion, groups did not differ among sleep quality components (all p's>.05). Conclusions: These findings revealed that nontreatment-seeking cannabis-using adolescents and young adults reported heightened total withdrawal symptoms during a 3-week sustained abstinence period relative to controls. Cannabis-using participants demonstrated an increase in withdrawal symptom trajectory during the first week followed by decreased symptoms from weeks 2 to 3, which contrasts with prior linear decreases observed in cannabis-using adolescent and young adults. More mood symptoms were observed in the cannabis-using group even while excluding for comorbid psychopathologies-along with significantly more sleep problems during the abstinence period. Implications include the necessity to provide psychoeducation for recreational, nontreatment-seeking cannabis-using individuals about cannabis withdrawal, mood symptoms, and sleep quality difficulties when cannabis cessation is attempted, to improve likelihood of long-term sustained abstinence.

Effects of 28 days of cannabis abstinence on cognition in major depressive disorder: A pilot study

BACKGROUND AND OBJECTIVES

Cannabis is a widely used substance that may impair select cognitive domains, including attention and memory. Problematic cannabis use is a common clinical problem among patients with major depressive disorder (MDD). Few studies have investigated the effects of cannabis abstinence on cognition in MDD. Thus, our study aimed to determine whether a 28-day period of cannabis abstinence is associated with improvements in cognition in patients with MDD and comorbid cannabis use disorder (CUD).

METHODS

We evaluated the effects of 28 days of cannabis abstinence on cognition in MDD patients with comorbid CUD facilitated by contingency management, motivational interviewing, psychoeducation, and coping-skills training (N = 11). Primary outcomes included Baseline to Day 28 changes in verbal memory and learning, while secondary outcomes included Baseline to Day 28 changes in working memory, visuospatial working memory (VSWM), visual search speed, mental flexibility, response inhibition, attention, manual dexterity, and fine motor movement.

RESULTS

Eight participants (72.7%) met the pre-specified criteria for cannabis abstinence and three participants significantly reduced their cannabis use (≥90%). Visual search speed, selective attention, and VSWM improved over the study period. These improvements were not associated with changes in cannabis metabolite levels from baseline to endpoint.

DISCUSSION AND CONCLUSIONS

Our findings suggest that 28 days of cannabis abstinence may improve select cognitive domains in patients with MDD and comorbid CUD.

SCIENTIFIC SIGNIFICANCE

This is the first study to longitudinally examine the effects of cannabis on cognition in MDD.

CLINICAL TRIAL

Effects of Cannabis Abstinence on Symptoms and Cognition in Depression (NCT03624933; https://www.

CLINICALTRIALS

gov).

Cannabis smoking increases the risk of suicide ideation and suicide attempt in young individuals of 11-21 years: A systematic review and meta-analysis

BACKGROUND

Cannabis is the most frequently consumed drug around the world. Its use has been associated with increased suicide behaviors; nonetheless, the association of cannabis smoking and suicide behaviors in adolescents has not yet been established. The aim of this systematic review and meta-analysis was to evaluate the risk of suicide attempt, suicidal ideation or suicide planning in individuals of 11-21 years of age who smoke cannabis.

METHODS

We performed an online searched using PubMed, EBSCO and Science Direct databases, up to July 2021. We calculated odds ratio with 95% confidence intervals to evaluate the association between suicide attempt, suicidal ideation or suicide planning and cannabis smoking in individuals of 11-21 years of age.

RESULTS

Twenty studies reported suicide attempts in 34,859 young individuals, suicidal ideation in 26, 937 individuals, and suicide planning in 9054 young individuals. We found an increased risk of suicide attempt in cannabis smokers than in non-cannabis users (OR: 2.33; 95% CI: 1.78-3.05; Z p value; <0.0001; I² = 97.12%), as well as a significant association between cannabis smoking and suicidal ideation (OR: 2.04; 95%CI: 1.64-2.53; Z p value: <0.001; I²: 94.88) and suicide planning (OR: 1.674; 95% CI: 1.554-1.804; Z p value: 0.000; I²: 92.609). Subgroup analyses showed that American teens have an increased risk of suicidal ideation; the meta-regression analysis revealed that age was negatively associated with the risk of suicide attempt.

CONCLUSIONS

This meta-analysis shows that cannabis smoking increased the risk of suicide attempt, suicidal ideation and suicide planning in young individuals of 11-21 years of age. The high risk of suicide behaviors could vary depending on the population studied; therefore, more studies are necessary to corroborate the risk of presenting suicide behaviors in individuals of 11-21 years of age who smoke cannabis.

Remote detection of Cannabis-related impairments in performance?

RATIONALE

Researchers have traditionally studied the effects of psychoactive drugs such as Cannabis in controlled laboratory settings or relied on retrospective self-reports to measure impairment. However, advances in technology afford opportunities to conduct assessments remotely.

OBJECTIVES

We considered whether objective click-stream data (time and number of clicks spent on a webpage) during an online survey could supplement self-reports of substance use problems.

METHODS

The clickstream data of participants (n = 236) were examined as they completed an online study which included validated psychometric tests (Cannabis Use Disorders Identification Test-Revised, Grit-O, Kessler Psychological Distress Scale, and Brief Self Control Scale). Clickstream data were compared to self-reported Cannabis use.

RESULTS

People reporting Cannabis use within the last 4 weeks required more time and more clicks to complete the online survey, and this was specifically associated with reported frequency of use, duration of impairment, and problems with memory and concentration. Longer amounts of time and more clicks on the online questionnaire were associated with more recent Cannabis use rather than demographic factors or stimulant use.

CONCLUSIONS

These results imply clickstream data remotely detected indecision or other deficits associated with previous Cannabis use.

Evidence on the acute and residual neurocognitive effects of cannabis use in adolescents and adults: a systematic meta-review of meta-analyses

BACKGROUND

Cannabis is among the most consumed psychoactive substances world-wide. Considering changing policy trends regarding the substance, it is crucial to understand more clearly its potential acute and residual adverse effects from a public health viewpoint. Cognitive function is one of the targeted areas with conflicting findings. This meta-review measured the magnitude of acute and residual effects of cannabis on cognition in adolescents and adults provided by meta-analyses and evaluated quality of evidence.

METHODS

A systematic search was performed in PubMed, PsycINFO, Web of Science and Google Scholar. Meta-analyses were included if they quantitatively examined the performances of users from the general population on cognitive tasks.

RESULTS

The search retrieved 10 eligible meta-analyses (71 effects sizes, n = 43 761) with evidence ranging from low to moderate quality, which were categorized into domains of cognitive functions: executive functions (k = 7), learning and memory (k = 5), attention (k = 4), processing speed (k = 5), perceptual motor function (k = 2) and language (k = 2). Verbal learning and memory displayed the most robust evidence and were most impaired by acute cannabis intoxication that persisted after intoxication passed. Small-to-moderate acute and residual   adverse effects were reported for executive functioning. Cannabis use led to small deficits in inhibitory processes and flexibility, whereas small-to-moderate deficits were reported for working memory and decision-making. Evidence regarding processing speed and attention has shown that cannabis administration induced small-to-moderate adverse effects and residual neurocognitive deficits were observed in heavy cannabis-using youths. Results showed no significant difference between cannabis users and non-users on language, and small-to-moderate effects for simple motor skills.

CONCLUSION

Meta-analytical data on the acute effects of cannabis use on neurocognitive function have shown that cannabis intoxication leads to small to moderate deficits in several cognitive domains. These acute impairments accord with documented residual effects, suggesting that the detrimental effects of cannabis persist beyond acute intake.

Resting-state EEG, Substance use and Abstinence After Chronic use: A Systematic Review

Resting-state EEG reflects intrinsic brain activity and its alteration represents changes in cognition that are related to neuropathology. Thereby, it provides a way of revealing the neurocognitive mechanisms underpinning chronic substance use. In addition, it is documented that some neurocognitive functions can recover following sustained abstinence. We present a systematic review to synthesize how chronic substance use is associated with resting-state EEG alterations and whether these spontaneously recover from abstinence. A literature search in Medline, PsycINFO, Embase, CINAHL, Web of Science, and Scopus resulted in 4088 articles, of which 57 were included for evaluation. It covered the substance of alcohol (18), tobacco (14), cannabis (8), cocaine (6), opioids (4), methamphetamine (4), and ecstasy (4). EEG analysis methods included spectral power, functional connectivity, and network analyses. It was found that long-term substance use with or without substance use disorder diagnosis was associated with broad intrinsic neural activity alterations, which were usually expressed as neural hyperactivation and decreased neural communication between brain regions. Some studies found the use of alcohol, tobacco, cocaine, cannabis, and methamphetamine was positively correlated with these changes. These alterations can partly recover from abstinence, which differed between drugs and may reflect their neurotoxic degree. Moderating factors that may explain results inconsistency are discussed. In sum, resting-state EEG may act as a potential biomarker of neurotoxic effects of chronic substance use. Recovery effects awaits replication in larger samples with prolonged abstinence. Balanced sex ratio, enlarged sample size, advanced EEG analysis methods, and transparent reporting are recommended for future studies.

Adolescents are more sensitive than adults to acute behavioral and cognitive effects of THC

Increased cannabis availability has contributed to increased use with concomitant incidence of adverse effects. One risk factor for adverse drug reactions may be age. There is preclinical evidence that acute effects of delta-9-tetrahydrocannabinol (THC), the primary active constituent of cannabis, are greater during adolescence, but this has not been fully studied in humans. The present study sought to determine whether adolescent men and women are more sensitive than adults to acute THC. Adolescents aged 18-20 (N = 12) and adults aged 30-40 (N = 12), with less than 20 total lifetime uses of THC-containing products, received capsules of THC (7.5, 15 mg) and placebo across three study sessions in randomized order under double blind conditions. During each session, subjective, cardiovascular, behavioral, and EEG measures were obtained. Behavioral measures included Simple Reaction Time, Stop Task, Time Production and N-back and EEG measures included P300 amplitudes during an auditory oddball task and eyes-closed resting state. THC affected subjective state and heart rate similarly in both age groups. However, adolescents were more sensitive to performance impairing effects, exhibiting dose-dependent impairments on reaction time, response accuracy, and time perception. On EEG measures, THC dose-dependently decreased P300 amplitude in adolescents but not adults. Adolescents were more sensitive to behavioral and cognitive effects of THC, but not to cardiovascular effects or subjective measures. Thus, at doses that produce comparable ratings of intoxication, adolescents may exhibit greater cognitive impairment and alterations in brain function.

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.

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

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

Early Age of Cannabis Initiation and Its Association With Suicidal Behaviors

Background:

Suicide rates in the U.S. have continued to rise over the last 2 decades. The increased availability and broader legalization of cannabis is a public health concern, particularly among adolescents. The objective of this study was to examine the association between the age of cannabis initiation and lifetime suicidal ideations and attempts in a sample of adults aged 18 or older.

Methods:

Data are from the Collaborative Psychiatric Epidemiology Surveys (CPES), 2001 to 2003 (N = 15 238). The primary objective of the CPES was to collect data about the prevalence of mental disorders, impairments associated with these disorders, and their treatment patterns from representative samples of majority and minority adult populations in the U.S. Logistic regression analyses were conducted to test the association between cannabis initiation age (early ⩽14 years old; later >14 years old) and outcomes of lifetime suicide ideation and attempts. Cigarette use, cannabis use, gender, income, race, education, and age were controlled for the analyses.

Results:

Overall, 12.5% of participants reported suicide ideation, while 4.2% reported attempt. Early cannabis use was associated with a higher risk of suicide ideation (AOR = 3.32, 95% CI [2.75, 3.80]) than later cannabis use (AOR = 2.15, 95% CI [1.92, 2.39]). Early cannabis use was associated with a higher risk of suicide attempt (AOR = 4.38, 95% CI [3.48, 5.52]) than later cannabis use (AOR = 2.56, 95% CI [2.14, 3.06]). Wald chi-squared tests revealed significant differences between the early and late initiation for both ideation (χ2 = 26.99; P < .001) and attempts (χ2 = 26.02; P < .001).

Conclusions:

Significant associations were found between early initiation of cannabis and suicide behaviors. As suicide rates continue to rise, it is recommended that clinicians, treatment providers, and other professionals consider the use of cannabis at an early age as a risk for subsequent suicide behaviors.

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

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

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.

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.

Preliminary Evidence for Cannabis and Nicotine Urinary Metabolites as Predictors of Verbal Memory Performance and Learning Among Young Adults

OBJECTIVE

Verbal memory deficits are linked to cannabis use. However, self-reported episodic use does not allow for assessment of variance from other factors (e.g., cannabis potency, route of consumption) that are important for assessing brain-behavior relationships. Further, co-occurring nicotine use may moderate the influence of cannabis on cognition. Here we utilized objective urinary measurements to assess the relationship between metabolites of cannabis, 11-nor-9-carboxy-∆9-tetrahydrocannabinol (THCCOOH), and nicotine (cotinine) on verbal memory in young adults.

METHOD

Adolescents and young adults (n = 103) aged 16-22 completed urinary drug testing and verbal memory assessment (RAVLT). Linear regressions examined the influence of THCCOOH and cotinine quantitative concentrations, and their interaction, on RAVLT scores, controlling for demographics and alcohol. Cannabis intake frequency was also investigated. Secondary analyses examined whether past month or recency of use related to performance, while controlling for THCCOOH and cotinine concentrations.

RESULTS

THCCOOH concentration related to both poorer total learning and long delay recall. Cotinine concentration related to poorer short delay recall. Higher frequency cannabis use status was associated with poorer initial learning and poorer short delay. When comparing to self-report, THCCOOH and cotinine concentrations were negatively related to learning and memory performance, while self-report was not.

CONCLUSIONS

Results confirm the negative relationship between verbal memory and cannabis use, extending findings with objective urinary THCCOOH, and cotinine concentration measurements. No moderating relationship with nicotine was found, though cotinine concentration independently associated with negative short delay performance. Findings support the use of both urinary and self-report metrics as complementary methods in substance use research.

Differential Cognitive Performance in Females and Males with Regular Cannabis Use

OBJECTIVES

Preclinical and clinical studies suggest that males and females may be differentially affected by cannabis use. This study evaluated the interaction of cannabis use and biological sex on cognition, and the association between observed cognitive deficits and features of cannabis use.

METHODS

Cognitive measures were assessed in those with regular, ongoing, cannabis use (N = 40; 22 female) and non-using peers (N = 40; 23 female). Intelligence, psychomotor speed, and verbal working memory were measured with the Wechsler Abbreviated Scale of Intelligence, Digit Symbol Test, and Digit Span and Hopkins Verbal Learning Test, respectively. Associations between cognitive measures and cannabis use features (e.g., lifetime cannabis use, age of initiation, time since last use of cannabis, recent high-concentration tetrahydrocannabinoid exposure) were also evaluated.

RESULTS

No main effects of group were observed across measures. Significant interactions between group and biological sex were observed on measures of intelligence, psychomotor speed, and verbal learning, with greatest group differences observed between males with and without regular cannabis use. Psychomotor performance was negatively correlated with lifetime cannabis exposure. Female and male cannabis use groups did not differ in features of cannabis use.

CONCLUSIONS

Findings suggest that biological sex influences the relationship between cannabis and cognition, with males potentially being more vulnerable to the neurocognitive deficits related to cannabis use.

The Alerting and Orienting Systems of Attention Are Modified by Cannabis Dependence

Attention allows us to select relevant information from the background. Although several studies have described that cannabis use induces deleterious effects on attention, it remains unclear if cannabis dependence affects the attention network systems differently.

OBJECTIVES

To evaluate whether customary consumption of cannabis or cannabis dependence impacts the alerting, orienting, and executive control systems in young adults; to find out whether it is related to tobacco or alcohol dependence and if cannabis use characteristics are associated with the attention network systems.

METHOD

One-hundred and fifty-four healthy adults and 102 cannabis users performed the Attention Network Test (ANT) to evaluate the alerting, orienting, and executive control systems.

RESULTS

Cannabis use enhanced the alerting system but decreased the orienting system. Moreover, those effects seem to be associated with cannabis dependence. Out of all the cannabis-using variables, only the age of onset of cannabis use significantly predicted the efficiency of the orienting and executive control systems.

CONCLUSION

Cannabis dependence favors tonic alertness but reduces selective attention ability; earlier use of cannabis worsens the efficiency of selective attention and resolution of conflicts.

Naturalistic exploratory study of the associations of substance use on ADHD outcomes and function

BACKGROUND

Although Attention Deficit Hyperactivity Disorder (ADHD) is associated with an increased risk of substance use disorder (SUD), existing literature on how SUD interacts with ADHD outcomes is limited. This study investigates whether SUD among individuals with ADHD is associated with worse ADHD outcomes and prognosis, and the association between overall functioning and SUD. In addition, we seek to understand whether heavy cannabis use is a better predictor of poorer outcomes compared to SUD status alone.

METHOD

We conducted a retrospective analysis on 50 ADHD patient charts, which were allocated based on SUD status. Subgroup analysis was performed on the total sample population, with allocation based on heavy cannabis use. Mann-Whitney and Chi-Square tests were used for both the primary and subgroup analyses.

RESULTS

SUD status highly correlated with more ADHD-related cognitive impairments and poorer functional outcomes at the time of diagnosis. ADHD patients with comorbid ADHD-SUD scored significantly lower (p = < 0.0001) on objective cognitive testing (Integrated Auditory and Visual Continuous Performance Test (IVA/CPT)) than ADHD patients without SUD. The correlation with poorer ADHD outcomes was more pronounced when groups were allocated based on heavy cannabis use status; in addition to significantly lower IVA/CPT scores (p = 0.0011), heavy cannabis use was associated with more severe fine motor hyperactivity and self-reported hyperactivity/impulsivity scores (p = 0.0088 and 0.0172, respectively).

CONCLUSION

Future research is needed to determine how substance abuse can be a barrier to improved ADHD outcomes, and the effect cannabis and other substances have on cognitive function and pharmacotherapy of ADHD.

Distinct patterns of prefrontal cortical disengagement during inhibitory control in addiction: A meta-analysis based on population characteristics

Prefrontal cortical dysfunctions underlying inhibitory control deficits in addiction are complex and likely dependent on population characteristics. Here, we conducted a meta-analysis to examine alterations in brain activations during response inhibition in addicted individuals. We characterized imaging findings based on substance use status, diagnosis, substance classes, and task performance. Results revealed in those with active drug addiction hypoactivation of the left dorsal anterior cingulate cortex (dACC) and right middle frontal gyrus (MFG), compared with healthy controls. Weakening of the dACC and MFG activations was particularly pronounced in nicotine users, respectively. Impaired task performance was also associated with diminished MFG activation. In contrast, abstinent users did not exhibit any significant differences compared with healthy controls. Those with behavioral addictions were characterized by higher midcingulate cortical activation. Thus, the neural disengagement during response inhibition in active drug addiction was limited to a small number of prefrontal cortical regions and dependent on population characteristics. Finally, the evidence for potential normalization of hypofrontality following substance use cessation highlights the benefits of abstinence in restoring cerebral functions.

A longitudinal study of the impact of marijuana on adult memory function: Prenatal, adolescent, and young adult exposures

More Americans are using marijuana than in previous decades but there are concerns over its long-term impact on cognitive functioning, especially memory. The literature on marijuana use and cognitive functioning is mixed, with some studies showing recovery of functioning upon abstinence from the drug and others showing long-term effects that persist. The latter seems especially true for individuals who initiate marijuana at a younger age and engage in more chronic patterns of use. The goal of the current study is to use prospectively collected data on young adults from a prenatal cohort to determine if there is an effect of early and/or current marijuana use on young adult memory, controlling for prenatal exposure to marijuana use, childhood memory deficits, and other significant covariates of memory functioning. At the 22-year follow-up phase of the Maternal Health Practices and Child Development (MHPCD) study, 524 young adults (58% Black, 42% White, 52% female) completed the Wechsler Memory Scale-III. Multiple regression analyses and structural equation modeling were used to determine the effect of marijuana exposure during gestation, early adolescence, and young adulthood on young adult memory function. Results indicated that initiating marijuana use before age 15 placed young adults at greater risk of memory deficits, even after controlling for childhood memory and current marijuana use. First trimester marijuana exposure also indirectly predicted young adult memory function via childhood memory deficits and early initiation of marijuana. These findings highlight the risk of prenatal marijuana exposure and early initiation of marijuana for long-term memory function in adulthood.

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.

Cannabis and Cognitive Functioning: From Acute to Residual Effects, From Randomized Controlled Trials to Prospective Designs

In recent years, several jurisdictions have revised their regulation policy toward both medical and recreational use of cannabis. These changes have elicited concerns regarding how legalization impacts academic achievement and work performance. This review evaluates the acute and long-term (residual) association between cannabis use and cognitive functioning that underlies poor academic and work performance. Relative to other reviews, this article focuses on cross-over randomized controlled trials and prospective designs given that they allow to test the impairing effects of cannabis exposure at the within-subject level. Acute cannabis cognitive effects are discussed separately for known confounding factors such as levels of delta-9-tetrahydrocannabinol (Δ⁹-THC), Δ⁹-THC:cannabidiol ratio, previous cannabis use and, comorbidity with psychosis-spectrum disorders. The cognitive residual effects of cannabis are detailed in relation to duration of abstinence, frequency of use, comorbidity with psychosis-spectrum disorders, types of cognitive domains assessed, and age of cannabis use initiation. Moreover, considering the fact that adequate longitudinal studies can make inferences about causality between cannabis use and impaired cognitive functioning when disentangling between-subject from within-subject variation, proofs for the three main non-mutually exclusive hypotheses about this relationship will be presented: i) the cognitive vulnerability hypothesis as part of the more general common antecedent hypothesis, ii) the concurrent cannabis impairing hypothesis, and iii) the neurotoxic hypothesis of cannabis. Current research provides evidence for mild to moderate acute cannabis effects on episodic and working memory, processing speed, and executive functions. Mild residual impairing effects were also observed in these exact same cognitive domains, suggesting that adverse effects following cannabis intoxication persist at least days or weeks following cannabis abstinence. Relative to adult-onset, adolescent-onset cannabis use seems to explain the dose-response relationship and is associated with longer lasting residual effects even in mild users (<weekly). The association between cannabis and cognition is likely explained by common antecedents, such that genetic and shared environment factors predispose individuals to both cannabis use and cognitive deficits, and to a lesser degree, neurotoxic effects.

Investigating the Residual Effects of Chronic Cannabis Use and Abstinence on Verbal and Visuospatial Learning

Rationale: Regular cannabis users have been shown to differ from non-using controls in learning performance. It is unclear if these differences are specific to distinct domains of learning (verbal, visuospatial), exacerbate with extent of cannabis exposure and dissipate with sustained abstinence. Objective: This study examines different domains of learning (verbal, visuospatial) in current and abstaining cannabis users, and the role of chronicity of use. Methods: In a cross-sectional design, we examined 127 psychiatrically healthy participants (65 female) with mean aged of 34 years. Of these, 69 individuals were current regular cannabis users (mean 15 years use), 12 were former cannabis users abstinent for ~2.5 yrs (after a mean of 16 years use), and 46 were non-cannabis using controls. Groups were compared on verbal learning performance assessed via the California Verbal Learning Test (CVLT-II) and for visuospatial learning measured with the Brown Location Test (BLT). We explored the association between CVLT/BLT performance and cannabis use levels in current and former users. Results: Current cannabis use compared to non-use was associated with worse performance on select aspects of verbal learning (Long Delay Cued Recall) and of visuospatial learning (Retroactive Interference and LD Rotated Recall). Prolonged abstinence was associated with altered verbal learning but intact visuospatial learning. There were non-significant correlations between distinct cannabis use measures, age and learning in both current and former users. Conclusions: Our findings suggest cannabis use status (current use, former use) affects different domains of learning (verbal and visuospatial) in a distinct fashion. These findings might be accounted for in the design of cognitive interventions aimed to support abstinence in cannabis users.

Cognition and Cortical Thickness in Heavy Cannabis Users

INTRODUCTION

Acute and long-term adverse effects of heavy cannabis use (HCU) on neurocognitive function have been suggested, as much as regional changes of brain volume. However, little is known about the relationship between impaired cognition and brain structure in individuals with HCU.

OBJECTIVE

Here, we investigated associations between cognition and cortical thickness (CT) in males with HCU and male controls.

METHODS

Twenty-six individuals with HCU and 20 controls were examined using a comprehensive neuropsychological test battery and high-resolution structural MRI at 3T. CT was calculated using the Computational Anatomy Toolbox (CAT12).

RESULTS

Individuals with HCU differed from controls with respect to verbal learning performance and verbal working memory only. Individuals with HCU showed reduced CT in medial temporal, orbitofrontal, and cingulate regions, as well as in areas of the middle temporal and fusiform cortex (peak voxel family-wise error-corrected p < 0.001, followed by empirically determined correction for spatial extent) compared to HC. Verbal learning performance was associated with right entorhinal and left orbitofrontal CT reductions. Entorhinal CT was also significantly associated with amount and frequency of current weekly cannabis use.

CONCLUSIONS

The data support the notion of domain-specific cognitive impairment in individuals with HCU and provide a neuromechanistic understanding of such deficits, particularly with respect to abnormal CT in brain areas associated with long-term memory processing.

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.

Implications of Medical and Recreational Marijuana Laws for Neuroscience Research: a Review

Purpose of Review

Review of US medical and recreational marijuana laws (MML and RML), their effects on cannabis potency, prevalence of non-medical cannabis use and cannabis use disorder (CUD) in adolescents and adults, and implications for neuroscience research, given what is known about the relationship of cannabis to neurocognitive impairments and underlying brain functioning.

Recent Findings

Cannabis potency may be increasing faster in states with MML or RML than in other states. MML and RML have not impacted prevalence in adolescents but have consistently been shown to increase rates of adult non-medical use and CUD.

Summary

Recent neurocognitive or neuroimaging studies may be more impacted by cannabis than studies conducted when MML and RML were less common. Neurocognitive or neuroimaging studies conducted in MML or RML states should carefully test potential participants for recent cannabis use. More research is needed on cannabis and cognition in medical marijuana patients.

Impact of 2 Weeks of Monitored Abstinence on Cognition in Adolescent and Young Adult Cannabis Users

OBJECTIVES

Previous research suggests recovery from cannabis-related deficits in verbal learning and memory functioning after periods of cannabis abstinence in adolescents. Here, we examine how cannabis cessation affects cognitive performance over 2 weeks of monitored abstinence compared to controls in adolescents and young adults.

METHODS

Seventy-four participants (35 cannabis users) aged 16-26 ceased all cannabis, alcohol, and other illicit substance consumption for a 2-week period; abstinence was monitored via weekly urinalysis, breath, and sweat patch testing. Starting at baseline, participants completed weekly abbreviated neuropsychological batteries. Measures included tests of attention, inhibition, verbal working memory, and learning. Repeated measures assessed within and between subject effects for time and group status, while controlling for past year alcohol and nicotine use.

RESULTS

Cannabis users showed increased performance compared to controls on sustained attention tasks after 2 weeks of cannabis use.

CONCLUSIONS

Deficits in attention, but not verbal learning and memory, recovered after 2 weeks of monitored abstinence. This differs from previous literature, suggesting that other cognitive domains may show signs of recovery after periods of cannabis cessation in adolescents and young adults.

ADHD Is Highly Prevalent in Patients Seeking Treatment for Cannabis Use Disorders

Objective: To estimate the prevalence of ADHD and determine an effective screening test for ADHD in a population-seeking treatment for cannabis use disorders. Method: The Conners Adult ADHD Diagnostic Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV; CAADID) was used to generate sensitivity and specificity data for ADHD screening tests, which were then administered to 99 participants seeking treatment for cannabis use disorders to estimate ADHD prevalence. Results: The prevalence estimated from the Wender Utah Rating Scale (WURS) was 45% (sensitivity = 0.88, sensitivity of 0.75), from the Conners Adult ADHD Rating Scale (CAARS) 34% (sensitivity = 0.80, specificity = 0.91), from the WURS + CAARS 36% (sensitivity = 0.71, specificity = 0.95), and from the Adult ADHD Self-Report Scale (ASRS) 46% (sensitivity = 0.61, specificity = 0.86). Conclusion: The prevalence of ADHD in adults seeking treatment for cannabis use disorders is estimated to be between 34% and 46%. The WURS paired with the CAARS provides excellent sensitivity and specificity for the diagnosis of ADHD in this population.

Marijuana use and major depressive disorder are additively associated with reduced verbal learning and altered cortical thickness

Marijuana (MJ) use and major depressive disorder (MDD) have both been associated with deficits in verbal learning and memory as well as structural brain abnormalities. It is not known if MJ use by those with MDD confers additional impairment. The goal of this study was to examine unique and combined effects of MDD and MJ use on verbal memory and brain structure. Young adults (n=141) aged 18-25 years with MJ use and no lifetime MDD (MJ, n=46), MDD and no MJ use (MDD, n=23), MJ use and lifetime MDD (MDD+MJ, n=24), and healthy controls without MDD or MJ use (CON, n=48) were enrolled. Participants completed the California Verbal Learning Test, Second Edition (CVLT-II), a measure of verbal learning and memory. A sub-sample of 82 participants also underwent a structural magnetic resonance imaging (MRI) scan. Group differences in CVLT-II performance, cortical thickness, and hippocampal volume were assessed. We found an additive effect of MDD and MJ on memory recall. Only MDD, but not MJ, was associated with poorer initial learning, fewer words recalled, more intrusion errors, and lower percent retention. There was also an additive effect of MDD and MJ use on reduced cortical thickness in the middle temporal gyrus. Findings indicate that MJ use and MDD have additive adverse associations with verbal recall and cortical thickness in the middle temporal gyrus, suggesting that MJ use among those with MDD may be contraindicated. Prospective studies are warranted to determine whether this association may be causal.