Anormalidades cognitivas no uso da cannabis

The role of sleep in the link between cannabis use and memory function: evidence from a cross-sectional study

Background: It is known that cannabis use affects memory and sleep problems independently. However, to date, how memory and sleep problems may interact as a result of cannabis use remains unknown.Objectives: We performed a secondary analysis of existing data to determine whether sleep quality mediates the association between cannabis use and memory and whether sex moderated these effects.Methods: A total of 141 adults with cannabis use disorder (CUD) (83 men) and 87 without CUD (39 men) participated in this study. Outcome measures included self-reported sleep problems from the past 7 days (Marijuana Withdrawal Checklist), learning and memory performance via the short visual object learning task (sVOLT), short visual object learning task delayed (sVOLTd), and verbal memory via the N-back. Bootstrapped mediation and moderated mediation analyses were run to test if sleep quality mediated the association between cannabis use and memory outcomes and whether sex moderated these effects, respectively.Results: Sleep quality mediated the effect of group (i.e. adults with and without CUD) on sVOLT efficiency scores (indirect effect ß = -.08, 95% CI [-0.14, -0.04]) and sVOLTd efficiency scores (indirect effect ß = -.09, 95% CI [-0.14, -0.04]), where greater sleep difficulties was associated with poorer memory performance (decreased efficiency scores). Sex did not moderate these relationships.Conclusion: These initial findings of a mediating role of sleep in the association between CUD and visual learning memory highlight potential critical downstream effects of disrupted sleep in those with CUD and suggest the importance of investigating sleep in CUD.

Electrophysiological and behavioral correlates of cannabis use disorder

Current research indicates deficits in cognitive function together with widespread changes in brain activity following long-term cannabis use. In particular, cannabis use has been associated with excessive spectral power of the alpha rhythm (8-12 Hz), which is also known to be modulated during attentional states. Recent neuroimaging studies have linked heavy cannabis use with structural and metabolic changes in the brain; however, the functional consequences of these changes are still not fully characterized. This study investigated the electrophysiological and behavioral correlates of cannabis dependence by comparing patients with a cannabis use disorder (CUD; N = 24) with cannabis nonuser controls (N = 24), using resting state electroencephalogram (EEG) source-imaging. In addition to evaluating mean differences between groups, we also explored whether particular EEG patterns were associated with individual cognitive-behavioral measures. First, we replicated historical findings of elevated levels of (relative) alpha rhythm in CUD patients compared with controls and located these abnormalities to mainly prefrontal cortical regions. Importantly, we observed a significant negative correlation between alpha spectral power in several cortical regions and individual attentional performance in the Go/NoGo task. Because such relationship was absent in the nonuser control group, our results suggest that reduced prefrontal cortical activation (indexed by increased relative alpha power) could be partly responsible for the reported cognitive impairments in CUD. Our findings support the use of electroencephalography as a noninvasive and cost-effective tool for biomarker discovery in substance abuse and have the potential of directly informing future intervention strategies.

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.

Adolescent cannabinoid exposure interacts with other risk factors in schizophrenia: A review of the evidence from animal models

Many factors and their interaction are linked to the aetiology of schizophrenia, leading to the development of animal models of multiple risk factors and adverse exposures. Differentiating between separate and combined effects for each factor could better elucidate schizophrenia pathology, and drive development of preventative strategies for high-load risk factors. An epidemiologically valid risk factor commonly associated with schizophrenia is adolescent cannabis use. The aim of this review is to evaluate how early-life adversity from various origins, in combination with adolescent cannabinoid exposure interact, and whether these interactions confer main, synergistic or protective effects in animal models of schizophrenia-like behavioural, cognitive and morphological alterations. Patterns emerge regarding which models show consistent synergistic or protective effects, particularly those models incorporating early-life exposure to maternal deprivation and maternal immune activation, and sex-specific effects are observed. It is evident that more research needs to be conducted to better understand the risks and alterations of interacting factors, with particular interest in sex differences, to better understand the translatability of these preclinical models to humans.

Perseverative Responding in Nigerian Chronic Alcohol and Marijuana Users

Background: Chronic consumption of alcohol and marijuana, especially when initiated at an early age, has been implicated in cognitive alterations in the domain of executive functioning. Despite the robustness of this finding in Western populations, its generalizability to other cultural contexts is largely unknown. In this study, we examined whether the regular use of alcohol or marijuana use relates to impaired executive functioning in male students of a Nigerian university. Methods: Chronic alcohol users (n = 39), chronic marijuana users (n = 35) and drug-abstinent control participants (n = 40) recruited through snow-ball sampling technique completed a computerized version of the Wisconsin Card Sorting Test (cWCST). As an established measure of executive functioning, the cWCST allows for the simultaneous assessment of three distinct executive processes: set shifting, rule inference, and set maintenance. Results revealed a selective set-shifting deficit in both alcohol and marijuana users. Results: Both groups committed significantly more perseverative errors than the control group, and group differences were significantly stronger on this indicator of set shifting than on indicators of rule inference or set maintenance. Conclusions: Our findings support the generalizability of drug-related deficits in executive functioning and contribute to the characterization of executive dysfunction in non-Western populations. Future longitudinal studies are required to clarify whether executive dysfunction is an antecedent or consequence of alcohol and marijuana use in young Nigerians.

Reward, Control & Decision-Making in Cannabis Use Disorder: Insights from Functional MRI

The recreational consumption of cannabis has increased significantly across the world with an estimated 180 million people currently using. In the United States, 4.1 million are currently diagnosed with cannabis use disorder. Cannabis dependence and abuse was combined into a single entity as a behavioral disorder with a problematic pattern of cannabis use and termed cannabis use disorder by the Diagnostic and Statistical Manual of Mental Disorders. Chronic use of cannabis has been linked with region-specific effects across the brain mediating reward processing, cognitive control and decision-making that are central to understanding addictive behaviors. This review presents a snapshot of the current literature assessing the effects of chronic cannabis use on human brain function via functional MRI. Studies employing various paradigms and contrasting cognitive activation amongst cannabis users and non-users were incorporated. The effects of trans-del-ta-9-tetrahydrocannabinol (Δ9-THC) in marijuana and other preparations of cannabis are mediated by the endocannabinoid system, which is also briefly introduced.Much variation exists in the current literature regarding the functional changes associated with chronic cannabis use. One possible explanation for this variation is the heterogeneity in study designs, with little implementation of standardized diagnostic criteria when selecting chronic users, distinct time points of participant assessment, differing cognitive paradigms and imaging protocols. As such, there is an urgent requirement for future investigations that further characterize functional changes associated with chronic cannabis use.

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.

Beneficial and deleterious effects of cannabinoids in the brain: the case of ultra-low dose THC

This article reviews the neurocognitive advantages and drawbacks of cannabinoid substances, and discusses the possible physiological mechanisms that underlie their dual activity. The article further reviews the neurocognitive effects of ultra-low doses of ∆9-tetrahydrocannabinol (THC; 3-4 orders of magnitude lower than the conventional doses) in mice, and proposes such low doses of THC as a possible remedy for various brain injuries and for the treatment of age-related cognitive decline.

Does social context matter? An ecological momentary assessment study of marijuana use among college students

INTRODUCTION

Past research has shown that marijuana use occurs commonly in social situations for young adults, though few studies have examined the association between immediate social context and marijuana use patterns and associated problems. The current study examined the impact of demographics, marijuana use and problem use, alcohol use, craving, and social context on the likelihood of using marijuana with others via ecological momentary assessment (EMA).

METHODS

College-student marijuana users (N=56) were recruited and completed a baseline assessment and training on the two-week signal-contingent EMA protocol. Participants were sent text messages three times per day randomly for two weeks.

RESULTS

Of the 1131 EMA instances during which participants reported using marijuana, 862 (76.22%) were labeled as being with others. Forty-five participants (80.36%) reported marijuana use with others present during at least half of the times they used marijuana. Findings from a multilevel logistic regression model showed a significant positive association between the probability of using with others and minutes spent using marijuana (b=0.047, p<0.001), social facilitation (b=0.138, p<0.001), and DSM-IV diagnosis (dependence versus no diagnosis, b=1.350, p=0.047).

CONCLUSIONS

Cannabis dependence, more time using marijuana in the moment, and using for social facilitation purposes were positively associated with using marijuana in the context of being with others. Daily users had more variability in terms of the social context of their use. This study illustrates the complex relationship between social context and marijuana use.

Verbal Memory Performance and Reduced Cortical Thickness of Brain Regions Along the Uncinate Fasciculus in Young Adult Cannabis Users

Introduction: Memory impairment is one of the most commonly reported effects of cannabis use, especially among those who initiate use earlier, perhaps due to the effects of delta-9- tetrahydrocannabinol on cannabinoid (CB1) receptors in the brain. Studies have increasingly investigated whether cannabis use is associated with impairments in verbal memory, and with alterations in brain structures underlying verbal memory. The uncinate fasciculus (UF), a long-range white matter tract, connects regions with densely localized CB1 receptors that are important in verbal memory. This study investigated the impact of cannabis use on UF structures and its association with memory performance in young adult cannabis users (CU) and non-using controls (CON).

Materials and Methods: Nineteen CU and 22 CON completed a verbal memory task and a neuroimaging protocol, in which diffusion tensor imaging and structural scans were collected. We compared memory performance, diffusion and tractography measures of the UF, and cortical thickness of regions connected by the UF, between CU and CON. In regions showing a significant group effect, we also examined associations between verbal memory performance, cortical thickness, and age of onset of cannabis use.

Results: Compared to non-users, CU had worse memory performance, decreased fiber bundle length in the UF, and decreased cortical thickness of brain regions along the UF such as the entorhinal cortex and fusiform gyrus. Verbal memory performance was significantly associated with age of onset of cannabis use, indicating that those who initiated cannabis use at an earlier age performed worse. Cortical thickness of the entorhinal cortex was significantly correlated with age of first use and memory performance.

Conclusion: This study provides evidence that cannabis use, especially when initiated at a young age, may be associated with worse verbal memory and altered neural development along the UF. Reductions in cortical thickness in regions implicated in memory processes may underlie weaknesses in verbal memory performance.

Marijuana and Alcohol Use as Predictors of Academic Achievement: A Longitudinal Analysis Among Youth in the COMPASS Study

BACKGROUND

We tested the effect of initiating marijuana and alcohol use at varying frequencies on academic indices.

METHODS

In a sample of 26,475 grade 9-12 students with at least 2 years of linked longitudinal data from year 1 (Y1: 2012-2013), year 2 (Y2: 2013-2014), and year 3 (Y3: 2014-2015) of the COMPASS study, separate multinomial generalized estimating equations models tested the likelihood of responses to measures of academic goals, engagement, preparedness, and performance when shifting from never using alcohol or marijuana at baseline to using them at varying frequencies at follow -up.

RESULTS

Students who began using alcohol or marijuana were less likely to attend class regularly, complete their homework, achieve high marks, and value good grades, relative to their abstaining peers. Changing from abstaining to rare/sporadic-to-weekly drinking or rare/sporadic marijuana use predicted aspirations to continue to all levels of higher education, and initiating weekly marijuana use increased the likelihood of college ambitions, while more regular marijuana use reduced the likelihood of wanting to pursue graduate/professional degrees, over high school.

CONCLUSIONS

The importance of delaying or preventing substance use is evident in associations with student performance and engagement. The influence on academic goals varied by substance and frequency of initiated use.

Parental Substance Abuse As an Early Traumatic Event. Preliminary Findings on Neuropsychological and Personality Functioning in Young Drug Addicts Exposed to Drugs Early

Parental substance use is a major risk factor for child development, heightening the risk of drug problems in adolescence and young adulthood, and exposing offspring to several types of traumatic events. First, prenatal drug exposure can be considered a form of trauma itself, with subtle but long-lasting sequelae at the neuro-behavioral level. Second, parents' addiction often entails a childrearing environment characterized by poor parenting skills, disadvantaged contexts and adverse childhood experiences (ACEs), leading to dysfunctional outcomes. Young adults born from/raised by parents with drug problems and diagnosed with a Substance Used Disorder (SUD) themselves might display a particularly severe condition in terms of cognitive deficits and impaired personality function. This preliminary study aims to investigate the role of early exposure to drugs as a traumatic event, capable of affecting the psychological status of young drug addicts. In particular, it intends to examine the neuropsychological functioning and personality profile of young adults with severe SUDs who were exposed to drugs early in their family context. The research involved three groups, each consisting of 15 young adults (aged 18–24): a group of inpatients diagnosed with SUDs and exposed to drugs early, a comparison group of non-exposed inpatients and a group of non-exposed youth without SUDs. A neuropsychological battery (Esame Neuropsicologico Breve-2), an assessment procedure for personality disorders (Shedler-Westen Assessment Procedure-200) and the Symptom CheckList-90-Revised were administered. According to present preliminary results, young drug addicts exposed to drugs during their developmental age were characterized by elevated rates of neuropsychological impairments, especially at the expense of attentive and executive functions (EF); personality disorders were also common but did not differentiate them from non-exposed youth with SUDs. Alternative multi-focused prevention and intervention programs are needed for children of drug-misusing parents, addressing EF and adopting a trauma-focused approach.

The effects of cannabis on memory function in users with and without a psychotic disorder: findings from a combined meta-analysis

BACKGROUND

Effect of cannabis use on memory function is a contentious issue, with effects being different in healthy individuals and patients with psychosis.

METHOD

Employing a meta-analytic approach we investigated the effects of cannabis use on memory function in patients with psychosis and healthy individuals, and the effect of diagnosis, memory dimension and moderating factors. A total of 88 studies were identified through a systematic literature search, investigating healthy (n = 7697) and psychotic (n = 3261) individuals. Standardized mean differences between the cannabis user and non-user groups on memory tasks were estimated using random-effects models and the effect-size statistic Cohen's d. Effects of potential moderating factors were tested using mixed-effects models and subgroup analyses.

RESULTS

We found that cannabis use was associated with significantly (p ⩽ 0.05) impaired global (d = 0.27) and prospective memory (d = 0.61), verbal immediate (d = 0.40) and delayed (d = 0.36) recall as well as visual recognition (d = 0.41) in healthy individuals, but a better global memory (d = -0.11), visual immediate recall (d = -0.73) and recognition (d = -0.42) in patients. Lower depression scores and younger age appeared to attenuate the effects of cannabis on memory. Cannabis-using patients had lower levels of depression and were younger compared with non-using patients, whilst healthy cannabis-users had higher depression scores than age-matched non-users. Longer duration of abstinence from cannabis reduced the effects on memory in healthy and patient users.

CONCLUSIONS

These results suggest that cannabis use is associated with a significant domain-specific impairment in memory in healthy individuals but not in cannabis-using patients, suggesting that they may represent a less developmentally impaired subgroup of psychotic patients.

The impact of initiation: Early onset marijuana smokers demonstrate altered Stroop performance and brain activation

Marijuana (MJ) use is on the rise, particularly among teens and emerging adults. This poses serious public health concern, given the potential deleterious effects of MJ on the developing brain. We examined 50 chronic MJ smokers divided into early onset (regular MJ use prior to age 16; n=24) and late onset (age 16 or later; n=26), and 34 healthy control participants (HCs). All completed a modified Stroop Color Word Test during fMRI. Results demonstrated that MJ smokers exhibited significantly poorer performance on the Interference subtest of the Stroop, as well as altered patterns of activation in the cingulate cortex relative to HCs. Further, early onset MJ smokers exhibited significantly poorer performance relative to both HCs and late onset smokers. Additionally, earlier age of MJ onset as well as increased frequency and magnitude (grams/week) of MJ use were predictive of poorer Stroop performance. fMRI results revealed that while late onset smokers demonstrated a more similar pattern of activation to the control group, a different pattern was evident in the early onset group. These findings underscore the importance of assessing age of onset and patterns of MJ use and support the need for widespread education and intervention efforts among youth.

Safety and Toxicology of Cannabinoids

There is extensive research on the safety, toxicology, potency, and therapeutic potential of cannabis. However, uncertainty remains facilitating continued debate on medical and recreational cannabis policies at the state and federal levels. This review will include a brief description of cannabinoids and the endocannabinoid system; a summary of the acute and long-term effects of cannabis; and a discussion of the therapeutic potential of cannabis. The conclusions about safety and efficacy will then be compared with the current social and political climate to suggest future policy directions and general guidelines.

Marijuana use, craving, and academic motivation and performance among college students: An in-the-moment study

INTRODUCTION

Marijuana is the most commonly used illicit substance in the U.S., with high rates among young adults in the state of Colorado. Chronic, heavy marijuana use can impact cognitive functioning, which has the potential to influence academic performance of college students. It is possible that craving for marijuana may further contribute to diminished cognitive and affective functioning, thus leading to poor outcomes for students.

METHODS

College student marijuana users (n=57) were recruited based on heavy use and completed ecological momentary assessment (EMA) via text-messaging. The association between marijuana use and craving in a college setting was explored, as well as how these variables might relate to academic motivation, effort and success. The participants were sent text messages for two weeks, three times per day at random times.

RESULTS

A temporal association between craving and marijuana use was found, where momentary craving positively predicted greater marijuana use. Similarly, as craving levels increased, the number of minutes spent studying decreased at the next assessment point. A negative association between momentary craving for marijuana and academic motivation was found in the same moment. Greater academic self-efficacy positively predicted cumulative GPA, while average minutes spent smoking marijuana was negatively related.

CONCLUSIONS

Using EMA, marijuana craving and use were significantly related. These findings provide further evidence that heavy marijuana use is negatively associated with academic outcomes.

A positive association between anxiety disorders and cannabis use or cannabis use disorders in the general population--a meta-analysis of 31 studies

BACKGROUND

The aim of the current study was to investigate the association between anxiety and cannabis use/cannabis use disorders in the general population.

METHODS

A total of N = 267 studies were identified from a systematic literature search (any time- March 2013) of Medline and PsycInfo databases, and a hand search. The results of 31 studies (with prospective cohort or cross-sectional designs using non-institutionalised cases) were analysed using a random-effects meta-analysis with the inverse variance weights. Lifetime or past 12-month cannabis use, anxiety symptoms, and cannabis use disorders (CUD; dependence and/or abuse/harmful use) were classified according to DSM/ICD criteria or scores on standardised scales.

RESULTS

There was a small positive association between anxiety and either cannabis use (OR = 1.24, 95% CI: 1.06-1.45, p = .006; N = 15 studies) or CUD (OR = 1.68, 95% CI: 1.23-2.31, p = .001; N = 13 studies), and between comorbid anxiety + depression and cannabis use (OR = 1.68, 95% CI: 1.17-2.40, p = .004; N = 5 studies). The positive associations between anxiety and cannabis use (or CUD) were present in subgroups of studies with ORs adjusted for possible confounders (substance use, psychiatric illness, demographics) and in studies with clinical diagnoses of anxiety. Cannabis use at baseline was significantly associated with anxiety at follow-up in N = 5 studies adjusted for confounders (OR = 1.28, 95% CI: 1.06-1.54, p = .01). The opposite relationship was investigated in only one study. There was little evidence for publication bias.

CONCLUSION

Anxiety is positively associated with cannabis use or CUD in cohorts drawn from some 112,000 non-institutionalised members of the general population of 10 countries.

Worth the wait: effects of age of onset of marijuana use on white matter and impulsivity

RATIONALE

Marijuana (MJ) use continues to rise, and as the perceived risk of using MJ approaches an all-time historic low, initiation of MJ use is occurring at even younger ages. As adolescence is a critical period of neuromaturation, teens and emerging adults are at greater risk for experiencing the negative effects of MJ on the brain. In particular, MJ use has been shown to be associated with alterations in frontal white matter microstructure, which may be related to reports of increased levels of impulsivity in this population.

OBJECTIVES

The aim of this study was to examine the relationship between age of onset of MJ use, white matter microstructure, and reported impulsivity in chronic, heavy MJ smokers.

METHODS

Twenty-five MJ smokers and 18 healthy controls underwent diffusion tensor imaging and completed the Barratt Impulsiveness Scale. MJ smokers were also divided into early onset (regular use prior to age 16) and late onset (age 16 or later) groups in order to clarify the impact of age of onset of MJ use on these variables.

RESULTS

MJ smokers exhibited significantly reduced fractional anisotropy (FA) relative to controls, as well as higher levels of impulsivity. Earlier MJ onset was also associated with lower levels of FA. Interestingly, within the early onset group, higher impulsivity scores were correlated with lower FA, a relationship that was not observed in the late onset smokers.

CONCLUSIONS

MJ use is associated with white matter development and reported impulsivity, particularly in early onset smokers.

Chronic effects of cannabis use on the auditory mismatch negativity

BACKGROUND

Cannabis use is associated with the development of psychotic symptoms and increased risk for schizophrenia. The mismatch negativity (MMN) is a brain event-related potential marker of change detection thought to index glutamatergic N-methyl-D-aspartate receptor-mediated neurotransmission, which is known to be deficient in schizophrenia. This study examined auditory MMN in otherwise healthy chronic cannabis users compared with nonuser control subjects.

METHODS

Forty-two chronic cannabis users and 44 nonuser healthy control subjects completed a multi-feature MMN paradigm, which included duration, frequency, and intensity deviants (deviants 6%; standards 82%). The MMN was compared between users and control subjects as well as between long- and short-term users and age- and gender-matched control subjects. Associations between MMN, cannabis use measures, and symptoms were examined.

RESULTS

The MMN amplitude was significantly reduced to frequency but not duration or intensity deviants in overall cannabis users relative to control subjects. Frequency MMN was similarly attenuated in short- and long-term users relative to control subjects. Long-term users also exhibited reduced duration MMN relative to control subjects and short-term users and this was correlated with increased duration of exposure to cannabis and increased psychotic-like experiences during intoxication. In short-term users, a younger age of onset of regular cannabis use and greater frequency of use were associated with greater psychotic-like experiences and symptomatic distress.

CONCLUSIONS

These results suggest impaired sensory memory that might reflect N-methyl-D-aspartate receptor dysfunction in chronic cannabis users. The pattern of MMN alterations in cannabis users differed from that typically observed in patients with schizophrenia, indicating overlapping but distinct underlying pathology.

Cannabis use and cognitive functions in at-risk mental state and first episode psychosis

BACKGROUND

Meta-analyses suggest that schizophrenia patients with a history of cannabis use have less impaired cognitive functioning compared to patients without cannabis use.

AIMS

The objective of this study was to assess the association between recency and frequency of cannabis use and cognitive functioning in at-risk mental state for psychosis (ARMS) and first episode psychosis (FEP) individuals.

METHODS

One hundred thirty-six participants completed a cognitive test battery and were assessed for current and past cannabis use. Analyses of covariance models were applied to evaluate the main effects of cannabis use and patient group (ARMS vs. FEP) as well as their interactions on cognitive functioning.

RESULTS

No differences were observed in cognitive performance between current, former, and never users, and there were no significant interactions between cannabis use and patient group. Furthermore, within the group of current cannabis users, the frequency of cannabis use was not significantly associated with cognitive functioning.

CONCLUSION

The results of the present study do not support the notion that FEP patients and ARMS individuals with a history of cannabis use have less impaired cognitive functioning compared to those without cannabis use.

Working memory and impulsivity predict marijuana-related problems among frequent users

BACKGROUND

Although marijuana is the most commonly used illicit substance in the US, only a small portion of users go on to develop dependence, suggesting that there are substantial individual differences in vulnerability to marijuana-related problems among users. Deficits in working memory and high trait impulsivity are two factors that may place marijuana users at increased risk for experiencing related problems.

METHODS

Using baseline data from an experimental study that recruited 104 frequent marijuana users (M=71.86% of prior 60 days, SD=22%), we examined the associations of working memory and trait impulsivity with marijuana-related problems.

RESULTS

Lower working memory, as measured by Trail Making Test B, but not short-term memory capacity, predicted more marijuana-related problems. Higher trait impulsivity scores were independently associated with greater number of problems.

CONCLUSIONS

Results suggest that marijuana users with reduced executive cognitive ability are more susceptible to developing problems related to their use. Trait impulsivity and executive working memory appear to be independent risk factors for experiencing marijuana-related problems.

Effects of cannabis on neurocognitive functioning: recent advances, neurodevelopmental influences, and sex differences

Decades of research have examined the effects of cannabis on neurocognition. Recent advances in this field provide us with a better understanding of how cannabis use influences neurocognition both acutely (during intoxication) and non-acutely (after acute effects subside). Evidence of problems with episodic memory is one of the most consistent findings reported; however, several other neurocognitive domains appear to be adversely affected by cannabis use under various conditions. There is significant variability in findings across studies, thus a discussion of potential moderators is increasingly relevant. The purpose of this review was to 1) provide an update on research of cannabis' acute and non-acute effects on neurocognition, with a focus on findings since 2007 and 2) suggest and discuss how neurodevelopmental issues and sex differences may influence cannabis effects on neurocognition. Finally we discuss how future investigations may lead to better understanding of the complex interplay among cannabis, stages of neurodevelopment, and sex on neurocognitive functioning.

Delayed preattentional functioning in early psychosis patients with cannabis use

RATIONALE

Cannabis use is prevalent among the early psychosis (EP) population. The event-related potentials, mismatch negativity (MMN) and P3a are reduced in EP. Cannabinoids have been shown to modulate N-methyl-D-aspartate receptors which are involved in MMN generation.

OBJECTIVES

This study is the first to investigate the effects of cannabis use on MMN/P3a in EP.

METHODS

EP was defined as a history of psychosis or psychotic symptoms with no progression to date to chronic schizophrenia. Twenty-two EP patients with cannabis use (EP + CANN), 22 non-cannabis-using EP patients (EP-CANN) and 21 healthy controls participated in this study. MMN/P3a was elicited using a two-tone, auditory paradigm with 8% duration deviants.

RESULTS

As expected, EP-CANN showed marked reductions in MMN/P3a amplitudes compared to controls. However, EP + CANN showed evidence of a different pattern of neurophysiological expression of MMN/P3a compared to non-using patients, most notably in terms of delayed frontal MMN/P3a latencies.

CONCLUSIONS

This study provides further evidence that MMN/P3a deficits are present during early psychosis and suggests that this biomarker may have utility in differentiating substance- from non-substance-related psychoses.

Adolescent exposure to cannabis as a risk factor for psychiatric disorders

Adolescence represents a critical period for brain development and the endocannabinoid system plays a crucial role in the regulation of neuronal refinement during this period. Cannabis is the most consumed drug among adolescent people and its heavy use may affect maturational refinement by disrupting the regulatory role of the endocannabinoid system. In animals, adolescent cannabinoid exposure has been reported to cause long-term impairment in specific components of learning and memory and to differentially affect emotional reactivity with milder effects on anxiety behaviour and more pronounced effects on depression-like behaviour. Moreover, adolescent exposure to cannabinoids might represent a risk factor for developing psychotic-like symptoms at adulthood. Also epidemiological studies suggest that heavy adolescent cannabis use may increase the risk of cognitive abnormalities, psychotic illness, mood disorders and other illicit substance use later in life. In conclusion, the available data point to the hypothesis that heavy cannabis use in adolescence could increase the risk of developing psychiatric disorders, especially in people who already have a vulnerability to develop a psychiatric syndrome. Only few papers have investigated the neurobiological substrates of this vulnerability, thus further studies are needed to clarify the molecular mechanisms underlying the effect of cannabis on the adolescent brain.

Verbal learning and memory in adolescent cannabis users, alcohol users and non-users

RATIONALE

Long-term heavy cannabis use can result in memory impairment. Adolescent users may be especially vulnerable to the adverse neurocognitive effects of cannabis.

OBJECTIVES AND METHODS

In a cross-sectional and prospective neuropsychological study of 181 adolescents aged 16-20 (mean 18.3 years), we compared performance indices from one of the most widely used measures of learning and memory--the Rey Auditory Verbal Learning Test--between cannabis users (n=52; mean 2.4 years of use, 14 days/month, median abstinence 20.3 h), alcohol users (n=67) and non-user controls (n=62) matched for age, education and premorbid intellectual ability (assessed prospectively), and alcohol consumption for cannabis and alcohol users.

RESULTS

Cannabis users performed significantly worse than alcohol users and non-users on all performance indices. They recalled significantly fewer words overall (p<0.001), demonstrating impaired learning (p<0.001), retention (p<0.001) and retrieval (p<0.05) (Cohen's d 0.43-0.84). The degree of impairment was associated with the duration, quantity, frequency and age of onset of cannabis use, but was unrelated to alcohol exposure or other drug use. No gender effects were detected and the findings remained after controlling for premorbid intellectual ability. An earlier age of onset of regular cannabis use was associated with worse memory performance after controlling for extent of exposure to cannabis.

CONCLUSIONS

Despite relatively brief exposure, adolescent cannabis users relative to their age-matched counterparts demonstrated similar memory deficits to those reported in adult long-term heavy users. The results indicate that cannabis adversely affects the developing brain and reinforce concerns regarding the impact of early exposure.

Vulnerability Factors for the Psychiatric and Behavioral Effects of Cannabis

Cogent evidence shows that cannabis plays a variable role on behavioral regulation and the pathophysiology of most psychiatric conditions. Accordingly, cannabis has been alternatively shown to exacerbate or ameliorate mental symptoms, depending on its composition and route of consumption, as well as specific individual and contextual characteristics. The vulnerability to the psychological effects of cannabis is influenced by a complex constellation of genetic and environmental factors. In the present article, we will review the current evidence on the pharmacological, individual and situational factors that have been documented to affect the behavioral and psychiatric effects of cannabinoids.