Neurophysiological functioning of occasional and heavy cannabis users during THC intoxication

Identifying standardised neuropsychological test measures sensitive to cannabis consumption: A systematic review

BACKGROUND

While numerous studies have indicated acute neurocognitive changes following the administration of Δ9-tetrahydrocannabinol (THC; the psychoactive component of cannabis), the standardised neuropsychological tests most sensitive to THC are yet to be identified. As such, this systematic review analysed scientific evidence (since 2000) on the effects of THC on standardised neuropsychological test measures.

METHODS

This review was conducted in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Studies were eligible for inclusion if they utilised a between or within-subjects design in testing for differences in standardised neuropsychological test performance following the consumption of THC.

RESULTS/DISCUSSION

Sufficient data were identified to examine 8 standardised neuropsychological test measures, with 12 studies being eligible for inclusion in the review. It was identified that the Cambridge Neuropsychological Test Automated Battery (CANTAB) subtest Spatial Working Memory, Hopkins Verbal Learning Test, Prose Recall and Rey Auditory Verbal Learning Test were sensitive to cannabis consumption.

LIMITATIONS

However, due to substantial variability observed across studies, the data could not be quantitatively analysed. It was noted that few studies employed standardised neuropsychological measures in assessing the effects of THC.

CONCLUSION

Overall, the findings highlight the need for further research examining the effects of cannabis on standardised and validated measures of neurocognitive function. Such an approach can be considered an important first step towards developing behavioural measures of impairment.

Does the stop-signal P3 reflect inhibitory control?

The ability to stop already-initiated actions is paramount to adaptive behavior. In psychology and neuroscience alike, action-stopping is a popular model behavior to probe inhibitory control - the underlying cognitive control process that is purportedly vital to regulating thoughts and actions. Starting with seminal work in the 1990s, the frontocentral stop-signal P3 - an event-related potential derived from scalp EEG - has been proposed as a neurophysiological index of inhibitory control during action-stopping. However, this association has been challenged repeatedly over recent years. Here, we perform a critical review of both the evidence in support of the association between this P3 index and inhibitory control, as well as its documented criticisms. We first comprehensively review literature from the past three decades that suggested a link between stop-signal P3 and inhibitory control. Second, we then replicate the key empirical patterns reported in that body of literature in a uniquely large stop-signal task EEG dataset (N = 255). Third, we then examine the criticisms raised against the view of P3 as an index of inhibitory control and evaluate the evidence supporting these arguments. Finally, we present an updated view of the process(es) reflected in the stop-signal P3. Specifically, we propose that the stop-signal P3 indexes a specific, selective inhibitory control process that critically contributes to action-stopping. This view is motivated by recent two-stage models of inhibitory control and emerging empirical data. Together, we hope to clarify the process(es) reflected in the stop-signal P3 and resolve the ongoing debates regarding its utility as an index of inhibitory control during action-stopping.

The acute effects of cannabis with and without cannabidiol in adults and adolescents: A randomised, double-blind, placebo-controlled, crossover experiment

BACKGROUND AND AIMS

Long-term harms of cannabis may be exacerbated in adolescence, but little is known about the acute effects of cannabis in adolescents. We aimed to (i) compare the acute effects of cannabis in adolescent and adult cannabis users and (ii) determine if cannabidiol (CBD) acutely modulates the effects of delta-9-tetrahydocannabinol (THC).

DESIGN

Randomised, double-blind, placebo-controlled, crossover experiment. The experiment was registered on ClinicalTrials.gov (NCT04851392).

SETTING

Laboratory in London, United Kingdom.

PARTICIPANTS

Twenty-four adolescents (12 women, 16- to 17-year-olds) and 24 adults (12 women, 26- to 29-year-olds) who used cannabis 0.5-3 days/week and were matched on cannabis use frequency (mean = 1.5 days/week).

INTERVENTION

We administered three weight-adjusted vaporised cannabis flower preparations: 'THC' (8 mg THC for 75 kg person); 'THC + CBD' (8 mg THC and 24 mg CBD for 75 kg person); and 'PLA' (matched placebo).

MEASUREMENTS

Primary outcomes were (i) subjective 'feel drug effect'; (ii) verbal episodic memory (delayed prose recall); and (iii) psychotomimetic effect (Psychotomimetic States Inventory).

FINDINGS

Compared with 'PLA', 'THC' and 'THC + CBD' significantly (P < 0.001) increased 'feel drug effect' (mean difference [MD] = 6.3, 95% CI = 5.3-7.2; MD = 6.8, 95% CI = 6.0-7.7), impaired verbal episodic memory (MD = -2.7, 95% CI = -4.1 to -1.4; MD = -2.9, 95% CI = -4.1 to -1.7) and increased psychotomimetic effects (MD = 7.8, 95% CI = 2.8-12.7; MD = 10.8, 95% CI = 6.2-15.4). There was no evidence that adolescents differed from adults in their responses to cannabis (interaction P ≥ 0.4). Bayesian analyses supported equivalent effects of cannabis in adolescents and adults (Bayes factor [BF01 ] >3). There was no evidence that CBD significantly modulated the acute effects of THC.

CONCLUSIONS

Adolescent cannabis users are neither more resilient nor more vulnerable than adult cannabis users to the acute psychotomimetic, verbal memory-impairing or subjective effects of cannabis. Furthermore, in adolescents and adults, vaporised cannabidiol does not mitigate the acute harms caused by delta-9-tetrahydocannabinol.

Novel Topical Anandamide Formulation for Alleviating Peripheral Neuropathic Pain

Peripheral neuropathy (PN) is a condition of peripheral nerve damage leading to severe pain. The first line therapies are associated with adverse psychotropic effects (PSE) and second line therapies are not efficient enough to relieve pain. There is an unmet drug need for relieving pain effectively without PSE in PN. Anandamide, an endocannabinoid activates cannabinoid receptors to relieve the pain due to peripheral neuropathy (PN). Anandamide has a very short biological half-life as they are extensively metabolized by fatty acid amide hydrolase enzyme (FAAH). Regional delivery of safe FAAH inhibitor (FI) with anandamide would be beneficial for PN without psychotropic effects. The objective of the study is to identify a safe FAAH inhibitor and deliver the anandamide in combination with the FAAH inhibitor topically for the management of PN. The FAAH inhibition potential of silymarin constituents was evaluated by molecular docking and in vitro studies. The topical gel formulation was developed to deliver anandamide and FI. The formulation was assessed in chemotherapeutic agent-induced peripheral neuropathy rat models to relieve mechanical-allodynia and thermal-hyperalgesia. The molecular docking studies demonstrated that the Prime MM-GBSA free energy of silymarin constituents were in the order of silybin > isosilybin > silychristin > taxifolin > silydianin. In in vitro studies, silybin 20 µM inhibited >61.8% of FAAH activity and increased the half-life of anandamide. The developed formulation increased permeation of anandamide and silybin across the porcine skin. Furthermore, on the application of anandamide and anandamide-silybin gel to rat paws, there was a significant increase in the pain threshold for allodynic and hyperalgesic stimulus up to 1 h and 4 h, respectively. The topical anandamide with silybin delivery approach could serve to alleviate peripheral neuropathy efficiently and thus could minimize unwanted CNS side effects of synthetic or natural cannabinoids in patients.

Cannabinoid-mediated targeting of mitochondria on the modulation of mitochondrial function and dynamics

Mitochondria play a critical role in the regulation of several biological processes (e.g., programmed cell death, inflammation, neurotransmission, cell differentiation). In recent years, accumulating findings have evidenced that cannabinoids, a group of endogenous and exogenous (synthetic and plant-derived) psychoactive compounds that bind to cannabinoid receptors, may modulate mitochondrial function and dynamics. As such, mitochondria have gained increasing interest as central mediators in cannabinoids' pharmacological and toxicological signatures. Here, we review the mechanisms underlying the cannabinoids' modulation of mitochondrial activity and dynamics, as well as the potential implications of such mitochondrial processes' disruption on cell homeostasis and disease. Interestingly, cannabinoids may target different mitochondrial processes (e.g., regulation of intracellular calcium levels, bioenergetic metabolism, apoptosis, and mitochondrial dynamics, including mitochondrial fission and fusion, transport, mitophagy, and biogenesis), by modulating multiple and complex signaling pathways. Of note, the outcome may depend on the experimental models used, as well as the chemical structure, concentration, and exposure settings to the cannabinoid, originating equivocal data. Notably, this interaction seems to represent not only an important feature of cannabinoids' toxicological signatures, with potential implications for the onset of distinct pathological conditions (e.g., cancer, neurodegenerative diseases, metabolic syndromes), but also an opportunity to develop novel therapeutic strategies for such pathologies, which is also discussed in this review.

Driving under the influence of cannabis: perceptions from Canadian youth

BACKGROUND

Cannabis legalization is intended to protect the public from potential harm by restricting access and promoting greater awareness of cannabis-related risks. Youth are at a greater risk for experiencing road-related harms due to their own or others' use of cannabis. This qualitative research explored youths' perceptions about cannabis and road safety.

METHODS

A qualitative study using focus groups (FG) was conducted with youth (age 13-18) and young adults (age 19-25) who resided in Newfoundland and Labrador. Using semi-structured interview questions, the facilitator asked participants to share their opinions about cannabis and road safety. All sessions were hosted virtually using Zoom with recruitment until saturation was met. All sessions were audio recorded, de-identified, and transcribed. Analysis utilized an inductive thematic approach informed by Braun and Clarke's (2006) method and inductive coding was facilitated using NVivo.

RESULTS

Six youth (n = 38) and five young adult (n = 53) FG were conducted. Five prominent themes emerged throughout discussions across both age groups including: a) normalization of driving under the influence of cannabis, b) knowledge and awareness, c) perceptions of risk, d) modes of transportation, and e) detection. Variation in perceptions appeared to be influenced by lack of awareness of the impact of cannabis on driving ability, residence in urban versus rural locations, type of vehicle driven (e.g., car vs. off-road vehicles), and gender.

CONCLUSION

The themes uncovered from this research will help inform future enhancement of cannabis policy to ensure the safety of all citizens. These findings will also support the inclusion of youth-focused education that will equip youth with informed decision-making strategies regarding road safety. Furthermore, these findings can be utilized to inform the refinement of cannabis driving policies to ensure the safety of all citizens on or off the road.

Effect of Lipid Vehicles on Solubility, Stability, and Topical Permeation of Delta-9-Tetrahydrocannabinol

Delta-9-tetrahydrocannabinol (THC) is one of the most effective antinociceptive agents used in the treatment of peripheral neuropathy. THC is highly lipophilic and susceptible to thermal and oxidative degradation. Identifying appropriate solvents in which THC is stable as well as adequately solubilized is crucial in developing topical dosage forms. Lipid solvent systems are of utmost utility and relevance for formulating highly lipophilic drugs. Hence, the objective of this project was to screen the solubility of THC in lipidic excipients, monitor THC content in the selected vehicles during stability, and study the influence of these excipients on permeation of THC across skin. The solubility of THC in liquid lipid excipients was in the range of 421 to 500 mg/g. The solubility of THC in solid lipid excipients was in the range of 250 to 750 mg/g. THC in its neat form was poorly stable, but when dissolved in lipid-based excipients, its stability improved significantly. THC in lipid excipients was more stable at 4 ± 3°C compared to samples stored at 25 ± 2°C. The antioxidants (butylated hydroxytoluene and ascorbyl palmitate) used in the excipients further improved the stability of THC. The results demonstrated that the liquid and solid lipid excipients used in the study could solubilize THC freely and mitigate the degradation of THC significantly. The binary combination of lipid excipients enhanced THC skin permeation and retention, demonstrating the potential for topical formulation development of THC.

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.

Neuroscience Outside the Box: From the Laboratory to Discussing Drug Abuse at Schools

One of the effects of the current COVID-19 pandemic is that low-income countries were pushed further into extreme poverty, exacerbating social inequalities and increasing susceptibility to drug use/abuse in people of all ages. The risks of drug abuse may not be fully understood by all members of society, partly because of the taboo nature of the subject, and partly because of the considerable gap between scientific production/understanding and communication of such knowledge to the public at large. Drug use is a major challenge to social development and a leading cause of school dropout rates worldwide. Some public policies adopted in several countries in recent decades failed to prevent drug use, especially because they focused on imposing combative or coercive measures, investing little or nothing in education and prevention. Here we highlight the role of neuroscience education as a valid approach in drug use education and prevention. We propose building a bridge between schools and scientists by promoting information, student engagement and honest dialogue, and show evidence that public policy regulators should be persuaded to support such science-based education programs in their efforts to effect important positive changes in society.

Psychotomimetic symptoms after a moderate dose of a synthetic cannabinoid (JWH-018): implications for psychosis

BACKGROUND

Synthetic cannabinoids (SCs) are the largest class of novel psychoactive substances (NPS) and are associated with an increased risk of overdosing and adverse events such as psychosis. JWH-018 is one of the earliest SCs and still widely available in large parts of the world. Controlled studies to assess the safety and behavioural profiles of SCs are extremely scarce.

AIM

The current study was designed to assess the psychotomimetic effects of a moderate dose of JWH-018.

METHODS

Twenty-four healthy participants (10 males, 14 females) entered a placebo-controlled, double blind, within-subjects trial and inhaled vapour of placebo or 75μg/kg bodyweight JWH-018. To ascertain a minimum level of intoxication, a booster dose of JWH-018 was administered on an as-needed basis. The average dose of JWH-018 administered was 5.52 mg. Subjective high, dissociative states (CADSS), psychedelic symptoms (Bowdle), mood (POMS) and cannabis reinforcement (SCRQ) were assessed within a 4.5-h time window after drug administration.

RESULTS

JWH-018 caused psychedelic effects, such as altered internal and external perception, and dissociative effects, such as amnesia, derealisation and depersonalisation and induced feelings of confusion.

CONCLUSION

Overall, these findings suggest that a moderate dose of JWH-018 induces pronounced psychotomimetic symptoms in healthy participants with no history of mental illness, which confirms that SCs pose a serious risk for public health.

Use of a Novel EEG-Based Objective Test, the Cognalyzer®, in Quantifying the Strength and Determining the Action Time of Cannabis Psychoactive Effects and Factors that May Influence Them Within an Observational Study Framework

INTRODUCTION

Current methods to detect recent delta-9-tetrahydrocannabinol (THC) use cannot objectively quantify its psychoactive effects (PE). The Cognalyzer®, an electroencephalography (EEG)-based method, detects and quantifies the strength of THC-induced PE on a scale from 0 to 100%. This study assesses the relationship between the magnitude of Cognalyzer® PE predictions and reported subjective drug effects for 4-h post-cannabis inhalation.

METHODS

Seventy-five participants were enrolled in the study. Prior to ad libitum cannabis inhalation, an EEG recording episode was completed. Immediately after inhalation, the Drug Effects Questionnaire (DEQ) was administered and another EEG recording performed. For 25 participants, the study ended. For 50 participants, assessments were repeated at 30-min intervals for 4 h. EEG files were blinded and analyzed using two versions of the Cognalyzer® algorithm. The relationship between the Cognalyzer® PE level results and the DEQ was assessed using generalized linear models and multiple regression.

RESULTS

There were significant PE increases from pre-cannabis for up to 3.5 h. Mean reports of feeling drug effects were > 0 at all post-inhalation time points (p ≤ 0.024). Furthermore, there were significant relationships between the Cognalyzer® PE and self-reported perception of drug effects (p ≤ 0.001). Subgroup analysis showed that Cognalyzer® PE levels were impacted by cannabis use history, subjective ratings of drug effects, oral fluid THC concentration and the cannabis product inhaled.

CONCLUSION

The findings show that the Cognalyzer® can be used to objectively determine the strength of cannabis psychoactive effects that cannabis products create on consumers and how it changes depending on their experience with cannabis. The Cognalyzer® can be used to conduct scientific consumer research to generate trustworthy informational material about the psychoactive experience of cannabis products. For clinical research, the Cognalyzer® can be used to study the pharmacodynamics of cannabinoids or delivery systems, such as nano-emulsifications.

Lateral habenula cannabinoid CB1 receptor involvement in drug-associated impulsive behavior

Animal and human studies show that cannabis or its derivatives can increase relapse to cocaine seeking following withdrawal. Moreover, cannabis use in humans is associated with impulse control deficits and animal studies implicate endogenous cannabinoids (eCB) in several impulsivity constructs. However, the brain areas where cannabinoids might control impulsivity or cocaine seeking are largely unknown. Here, we assess Lateral Habenula (LHb) involvement on performance in the 5-choice serial reaction time task (5CSRTT) in rats and investigate whether LHb cannabinoid CB1 receptors (CB1R) are involved in these effects. Systemic cocaine increased premature responding, a measure of impulsivity, at a dose (5 mg/kg) that did not alter other measures of task performance. Intra-LHb infusion of the CB1R antagonist AM251 blocked this effect. Systemic injection of the psychoactive constituent of cannabis, Δ⁹-tetrahydrocannabinol (Δ⁹-THC, 1 mg/kg), also increased 5CSRTT premature responding at a dose that did not otherwise disrupt task performance. This was blocked by intra-LHb infusion of AM251 in a subgroup of rats showing the largest increases in Δ⁹-THC-evoked premature responses. Systemic Δ⁹-THC also prompted impulsive cocaine seeking in a Go/NoGo cocaine self-administration task and this was blocked by intra-LHb AM251. These data show that LHb CB1Rs are involved in deficits in impulse control initiated by cocaine and Δ⁹-THC, as assessed by the 5CSRTT, and play a role in impulsive cocaine seeking during cocaine self-administration. This suggests that the LHb eCB system contributes to the control of impulsive behavior, and thus represents a potential target for therapeutic treatment of substance use disorders (SUDs) in humans.

Intoxication by a synthetic cannabinoid (JWH-018) causes cognitive and psychomotor impairment in recreational cannabis users

BACKGROUND

Smoking mixtures containing synthetic cannabinoids (SCs) have become very popular over the last years but pose a serious risk for public health. Limited knowledge is, however, available regarding the acute effects of SCs on cognition and psychomotor performance. Earlier we demonstrated signs of impairment in healthy volunteers after administering one of the first SCs, JWH-018, even though subjective intoxication was low. In the current study, we aimed to investigate the acute effects of JWH-018 on several cognitive and psychomotor tasks in participants who are demonstrating representative levels of acute intoxication.

METHODS

24 healthy cannabis-experienced participants took part in this placebo-controlled, cross-over study. Participants inhaled the vapor of 75 μg JWH-018/kg body weight and were given a booster dose if needed to induce a minimum level of subjective high. They were subsequently monitored for 4 h, during which psychomotor and cognitive performance, vital signs, and subjective experience were measured, and serum concentrations were determined.

RESULTS

Maximum subjective high (average 64%) was reached 30 min after administration of JWH-018, while the maximum blood concentration was shown after 5 min (8 ng/mL). JWH-018 impaired motor coordination (CTT), attention (DAT and SST), memory (SMT), it lowered speed-accuracy efficiency (MFFT) and slowed down response speed (DAT).

CONCLUSION

In accordance with our previous studies, we demonstrated acute psychomotor and cognitive effects of a relatively low dose of JWH-018.

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.

The Behavioral Sequelae of Cannabis Use in Healthy People: A Systematic Review

Background: Cannabis is known to have a broad range of effects on behavior, including experiencing a "high" and tranquility/relaxation. However, there are several adverse behavioral sequalae that can arise from cannabis use, depending on frequency of use, potency (e.g., THC content), age of onset, and cumulative exposure. This systematic review examined evidence for cannabis-related adverse behavioral sequalae in otherwise healthy human subjects. Methods: Following PRISMA guidelines, we conducted a systematic review of cross-sectional and longitudinal studies from 1990 to 2020 that identified cannabis-related adverse behavioral outcomes in subjects without psychiatric and medical co-morbidities from PubMed and PsychInfo searches. Key search terms included "cannabis" OR "tetrahydrocannabinol" OR "cannabidiol" OR "marijuana" AND "anxiety" OR "depression" OR "psychosis" OR "schizophrenia" "OR "IQ" OR "memory" OR "attention" OR "impulsivity" OR "cognition" OR "education" OR "occupation". Results: Our search detected a total of 2,870 studies, from which we extracted 124 relevant studies from the literature on cannabis effects in the non-clinical population. Effects of cannabis on several behavioral sequelae including cognition, motivation, impulsivity, mood, anxiety, psychosis intelligence, and psychosocial functioning were identified. The preponderance of the evidence suggests that frequency of cannabis use, THC (but not CBD) content, age of onset, and cumulative cannabis exposure can all contribute to these adverse outcomes in individuals without a pre-existing medical condition or psychiatric disorder. The strongest evidence for the negative effects of cannabis are for psychosis and psychosocial functioning. Conclusions: Although more research is needed to determine risk factors for development of adverse behavioral sequelae of cannabis use, these findings underline the importance of understanding vulnerability to the adverse effects of cannabis, which has implications for prevention and treatment of problematic cannabis use.

The short-term and long-term effects of cannabis on cognition: recent advances in the field

The aim of this review is to discuss the most recent evidence for the short-term and long-term effects of cannabis on cognition. The evidence that cannabis intoxication is associated with short-term impairment across several basal cognitive domains, including learning and (episodic) memory, attentional control, and motor inhibition is increasing. However, evidence regarding the effects of long-term heavy cannabis use on cognition remains equivocal. Cannabis research suffers from difficulties in measuring cannabis exposure history, poor control over potential subacute effects, and heterogeneity in cognitive measures and sample composition. Multidisciplinary collaborations and investment in studies that help overcome these difficulties should be prioritized.

Blunted highs: Pharmacodynamic and behavioral models of cannabis tolerance

Acute exposure to cannabis comes with neurocognitive impairment, leading to increased risk of human error and injury. Evidence however indicates that such acute effects are less prominent in chronic users, suggesting cannabis tolerance. Models of cannabis tolerance stress the importance of neurobiological or behavioral adaptations following repeated cannabis exposure. The pharmacodynamic model relates neuroadaptive changes in the brain to a blunted response to cannabis. Downregulation of CB1 receptors in chronic cannabis users has been associated with a normalization of dopaminergic output from the ventral tegmental area to the mesolimbic circuit, and a reduction of impairment during acute cannabis exposure. Such neuroadaptions are absent in occasional users, who show strong increments of dopamine and glutamate levels in the striatum, a loss of functional connectivity within the mesolimbic circuit and neurocognitive impairments when exposed to cannabis. Evidence for a behavioral model of cannabis tolerance that poses that users can have volitional control to overcome functional impairment during cannabis intoxication is relatively weak, and at best shows limited control over a limited number of behavioral functions. Cannabis tolerance is most likely to occur in users that consume high doses of cannabis continuously, at a high pace, for a prolonged period of time. Knowledge on frequency, dose and duration of cannabis use that is needed to achieve, maintain or lessen tolerance however is very limited, but will be of importance in the context of cannabis therapeutics and in legal settings when evaluating the impact of cannabis exposure on human function.

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

AIMS

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Daily patterns of substance use and violence among a high-risk urban emerging adult sample: Results from the Flint Youth Injury Study

OBJECTIVE

Interpersonal violence is a significant public health problem, with substance use a key risk factor. Intensive longitudinal methods (ILMs) provide data on daily patterns/relationships between substance use and violence, informing prevention. Prior daily research has not focused on these relationships among urban minority samples.

METHODS

Within an RCT comparing ILM assessment/schedule methods, 162-participants completed daily IVR (n = 81) or SMS (n = 81) assessments measuring 19 substance use and violence (partner/non-partner) behaviors daily for 90-days. GLMMs characterized between- and within-person predictors of daily violence.

RESULTS

Participants [48.7%-female; age = 24.4; 62.3%-African-American; 66.7%-public assistance] completed an average of 46.5 daily reports [SD = 26.7]. Across 90-days, alcohol was characterized by episodic weekend use (average = 10 days-of-use, 34.4% drinking-days involved binge-drinking), while marijuana use was continuous (average = 27 days-of-use; 1.7 times/day), with no weekend differences. Among 118-violent conflicts, 52.5% occurred on weekends; 57.6% were with non-partners/peers; 61.0% involved perpetration/57.6% victimization; and 52.5% involved severe violence. For violence conflicts, 27.1% were preceded by alcohol/22.9% preceded by drug use. Between-person predictors of daily violence included retaliatory attitudes (AOR = 3.2) and anxiety (AOR = 1.1). Within-person predictors included weekends (AOR = 1.6), binge drinking (AOR = 1.9), non-medical prescription opioid use (AOR = 3.5) and illicit drug use (AOR = 8.1).

CONCLUSION

Among a high-risk urban minority sample, we found that higher baseline retaliatory attitudes and anxiety, as well as same-day binge drinking, non-medical prescription opioid use, and illicit drug use were associated with daily violence, likely reflecting both pharmacological and socio-contextual factors. Addressing substance use and retaliatory violence with tailored prevention efforts may aid in decreasing negative interpersonal violence outcomes.

Cannabis induced increase in striatal glutamate associated with loss of functional corticostriatal connectivity

Cannabis is the most commonly used illicit drug and is known to alter state of consciousness and impair neurocognitive function. However, the mechanisms underlying these effects have yet to be fully elucidated. Rodent studies suggest that Δ9-tetrahydrocannabinol (THC) activates dopaminergic neurons in the limbic system, subsequently enhancing dopamine, which is implicated in the rewarding effects of cannabis. Additional evidence suggests that THC may act indirectly on dopamine firing by modulating GABA and glutamate release. This double-blind, placebo-controlled study assessed the acute influence of two doses of THC on brain kinetics of glutamate, GABA, and dopamine, in relation to behavioral outcomes, by using magnetic resonance spectroscopy and functional magnetic resonance imaging. Twenty occasional cannabis users received acute doses of cannabis (300 µg/kg THC) and placebo, in one of two dose regimes (full dose and divided dose), during two separate testing days. Administration of THC increased striatal glutamate concentrations, and dopamine as indicated by a reduction in functional connectivity (FC) between the nucleus accumbens (NAc) and cortical areas. Alterations in glutamate and FC were dose dependent and evident in the full dose group where THC serum concentrations exceeded 2 ng/ml at T-max. Average glutamate changes correlated strongly with FC alterations. Additionally, THC induced changes in FC correlated with feelings of subjective high and decreased performance on an attention task. Taken together, this suggests that THC elicits subjective and cognitive alterations via increased striatal dopaminergic activity and loss of corticostriatal connectivity, which is associated with an increase in striatal glutamate.

Impaired Recent Verbal Memory in Pornography-Addicted Juvenile Subjects

We aimed to find the differences in memory capabilities between pornography-addicted and nonaddicted juveniles. We enrolled 30 juveniles (12-16 y) consisting of 15 pornography addiction and 15 nonaddiction subjects. We used Rey Auditory Verbal Learning Test (RAVLT) to measure verbal memory, Rey-Osterrieth Complex Figure Test (ROCFT) for visual memory, along with Trail Making Test A and B (TMT-A and TMT-B) for attention. We found a significant reduction in the RAVLT A6 result of the addiction group (nonaddiction vs addiction: 13.47 ± 2.00 vs 11.67 ± 2.44, MD = -1.80, p=0.04), but not in ROCFT or attention tests. Analysis in sex subgroups yielded no sex-specific difference. We concluded that pornography addiction may be associated with impaired recent verbal memory in juveniles, regardless of sex and without association to attention.

Cannabis use as a risk factor for causing motor vehicle crashes: a prospective study

AIM

We conducted a responsibility analysis to determine whether drivers injured in motor vehicle collisions who test positive for Δ-9-tetrahydrocannabinol (THC) or other drugs are more likely to have contributed to the crash than those who test negative.

DESIGN

Prospective case-control study.

SETTING

Trauma centres in British Columbia, Canada.

PARTICIPANTS

Injured drivers who required blood tests for clinical purposes following a motor vehicle collision.

MEASUREMENTS

Excess whole blood remaining after clinical use was obtained and broad-spectrum toxicology testing performed. The analysis quantified alcohol and THC and gave semiquantitative levels of other impairing drugs and medications. Police crash reports were analysed to determine which drivers contributed to the crash (responsible) and which were 'innocently involved' (non-responsible). We used unconditional logistic regression to determine the likelihood (odds ratio: OR) of crash responsibility in drivers with 0 < THC < 2 ng/ml, 2 ng/ml ≤ THC < 5 ng/ml and THC ≥ 5 ng/ml (all versus THC = 0 ng/ml). Risk estimates were adjusted for age, sex and presence of other impairing substances.

FINDINGS

We obtained toxicology results on 3005 injured drivers and police reports on 2318. Alcohol was detected in 14.4% of drivers, THC in 8.3%, other drugs in 8.9% and sedating medications in 19.8%. There was no increased risk of crash responsibility in drivers with THC < 2 ng/ml or 2 ≤ THC < 5 ng/ml. In drivers with THC ≥ 5 ng/ml, the adjusted OR was 1.74 [95% confidence interval (CI) = 0.59-6.36; P = 0.35]. There was significantly increased risk of crash responsibility in drivers with blood alcohol concentration (BAC) ≥ 0.08% (OR = 6.00;95% CI = 3.87-9.75; P < 0.01), other recreational drugs detected (OR = 1.82;95% CI = 1.21-2.80; P < 0.01) or sedating medications detected (OR = 1.45; 95%CI = 1.11-1.91; P < 0.01).

CONCLUSIONS

In this sample of non-fatally injured motor vehicle drivers in British Columbia, Canada, there was no evidence of increased crash risk in drivers with Δ-9-tetrahydrocannabinol < 5 ng/ml and a statistically non-significant increased risk of crash responsibility (odds ratio = 1.74) in drivers with Δ-9-tetrahydrocannabinol ≥ 5 ng/ml.

A Survey of Cannabis Acute Effects and Withdrawal Symptoms: Differential Responses Across User Types and Age

Objectives: There is a rapidly evolving legal and medical culture around cannabis, with corresponding changes in the demographics of users. For instance, the percentage of the aging population accessing cannabis is growing substantially, outpacing other age groups. The goals of this study were to describe the acute effects of cannabis, subjective experiences of withdrawal, and beliefs around the addictiveness of cannabis, as well as to determine whether these effects differ as a function of age or reason for use (medical vs. recreational use). It was hypothesized that medical users and younger users would report fewer adverse effects.

Subjects: Survey responses from 2905 cannabis users were analyzed.

Results: Hierarchical logistic regression analyses were used to compare group percentages after statistically controlling for confounding differences in their demographic and cannabis use characteristics. The most commonly endorsed acute effects were improved sleep, more calm/peaceful, desire to eat, more creative, and dry mouth; while the most commonly endorsed withdrawal symptoms were irritability, insomnia, and anxiety. Relative to recreational users, medical users were less likely to report undesirable acute effects but were more likely to report undesirable withdrawal symptoms. Older (50+) individuals reported fewer undesirable acute effects and withdrawal symptoms compared with younger users (18–29). Only 17% of the total sample reported believing that cannabis is addictive, and this did not vary as a function of reason for use.

Conclusions: Older people and medical users appear to experience acute and withdrawal effects of cannabis differently than recreational and younger users, perhaps because these groups benefit more from the medicinal properties of cannabis. These data can provide descriptive information to help inform health care providers and potential consumers about effects of cannabis use.

Chronic Δ9-THC in Rhesus Monkeys: Effects on Cognitive Performance and Dopamine D2/D3 Receptor Availability

Cannabis-related impairments to cognitive function may represent novel therapeutic targets for cannabis-use disorder, although the nature, persistence, and reversibility of such deficits remain unclear. Adult male rhesus monkeys (N = 6) responded in the morning on tasks designed to assess different cognitive domains using the Cambridge Neuropsychological Test Automated Battery (CANTAB) touchscreens followed by responding maintained under a fixed-ratio (FR) 10 schedule of food presentation in different operant chambers. First, the acute effects of Δ⁹-tetrahydrocannabinol (THC; 0.01-0.56 mg/kg, i.v.) on cognitive performance, FR responding, and body temperature were determined. Next, THC (1.0-2.0 mg/kg, s.c.) was administered daily after FR 10 sessions for 12 weeks, during which the residual effects of THC (i.e., 22 hours after administration) on cognition were examined and the acute effects of THC were redetermined. In a subgroup of monkeys, dopamine D2/D3 receptor availability was assessed after 4 weeks of chronic THC exposure and compared with drug-naive controls using positron emission tomography and [¹¹C]-raclopride (N = 4/group). Acute THC pretreatments dose-dependently decreased FR responding and body temperature, and impairment to cognitive performance was task specific. During chronic treatment, THC produced persistent residual impairment only to working memory; tolerance differentially developed to acute cognitive impairments. There was recovery from residual cognitive impairments to working memory within 2 weeks of abstinence. Compared with controls, D2/D3 receptor availability was not altered during chronic THC treatment. In conclusion, THC-induced disruptions in cognition were task-specific, as was tolerance development, and not related to changes in D2/D3 receptor availability. Intervention strategies for cannabis-use disorder that enhance working memory performance may facilitate positive treatment outcomes.

Longitudinal changes in cognition in young adult cannabis users

INTRODUCTION

Adolescent cannabis use (CU) is associated with impaired attention, executive function, and verbal learning/memory. These associations are generally observed in cross-sectional studies. Longitudinal studies of cannabis users are lacking.

METHOD

The present study examines associations between CU and cognition over time in chronic daily adolescent-onset CUs, as compared to nonusing controls. Both groups completed a neuropsychological battery at study intake and again 2 years later.

RESULTS

Baseline group differences have been published and indicated deficits in verbal learning and memory, motivated decision-making, planning, and working memory in CUs. In this follow-up report, the longitudinal performance of users is compared to that of sustained nonusers using the same battery. At follow-up, the majority of CUs continued to report regular and heavy cannabis use. Relative impairments in the domains of working memory, planning and verbal memory remained stable, suggesting that these are enduring vulnerabilities associated with continued CU during young adulthood. Improvements in motivated decision-making were evident in both groups. In addition, CUs demonstrated relatively better performance on short-duration speeded tasks. An earlier age of CU onset was associated with poorer verbal learning and memory and planning performance over time.

CONCLUSIONS

Verbal learning and memory and planning processes, as well as their neural correlates, merit further scrutiny within etiological models of cannabis-induced cognitive impairments.

Effects of cannabis use and subclinical depression on the P3 event-related potential in an emotion processing task

The effects of residual cannabis use on emotional expression recognition and the P3 event-related potential in participants who scored highly for subclinical depression were investigated. Comparisons were made between participants who were classified as depressed or nondepressed cannabis users, depressed non-cannabis users and controls who neither used cannabis nor were characterized as being depressed. In an emotional expression recognition task, participants were asked to respond to faces depicting happy, angry, fearful, and neutral faces either implicitly, explicitly, or empathically. Residual cannabis use and mood was shown to modulate the P3 event related potential during the task. There was a significant reduction in the P3 amplitude between depressed and nondepressed participants. Residual cannabis use further reduced the P3 amplitude with the greatest deficits being associated with cannabis users who scored highly for subclinical depression. These effects were greatest for explicit and empathic processing of faces depicting negative emotions. We conclude from our study that cannabis and mood state interact to reduce the amplitude of the P3 which has been associated with attention to emotion.

Evaluation of divided attention psychophysical task performance and effects on pupil sizes following smoked, vaporized and oral cannabis administration

Establishing science-based driving per se blood Δ⁹ -tetrahydrocannabinol (THC) limits is challenging, in part because of prolonged THC detection in chronic, frequent users. Therefore, documenting observable signs of impairment is important for driving under the influence of drugs. We evaluated frequent and occasional cannabis smokers' performance on the modified Romberg balance, one leg stand (OLS), and walk and turn (WAT) tasks, and pupil size effects following controlled placebo (0.001% THC), smoked, vaporized and oral (6.9% [~50.4 mg] THC) cannabis administration. Significant effects following inhaled doses were not observed due to delayed tasks administration 1.5 and 3.5 h post-dose, but significant impairment was observed after oral dosing (blood THC concentrations peaked 1.5-3.5 h post-dose). Occasional smokers' odds of exhibiting ≥2 clues on the OLS or WAT following oral dosing were 6.4 (95% CI 2.3-18.4) times higher than after placebo, with THC and 11-hydroxy-THC blood concentrations individually producing odds ratios of 1.3 (1.1-1.5) and 1.5 (1.3-1.8) for impairment in these tasks, respectively. Pupil sizes after oral dosing under the direct lighting condition were significantly larger than after placebo by mean (SE, 95% CI) 0.4 (0.1, 0.2-0.6) mm at 1.5 h and 0.5 (0.2, 0.2-0.8) mm at 3.5 h among all participants. Oral cannabis administration impaired occasional cannabis users' performance on the OLS and WAT tasks compared to placebo, supporting other reports showing these tasks are sensitive to cannabis-related impairment. Occasional smokers' impairment was related to blood THC and 11-hydroxy-THC concentrations. These are important public health policy findings as consumption of edible cannabis products increases. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.

Acute effects of cocaine and cannabis on response inhibition in humans: an ERP investigation

Substance abuse has often been associated with alterations in response inhibition in humans. Not much research has examined how the acute effects of drugs modify the neurophysiological correlates of response inhibition, or how these effects interact with individual variation in trait levels of impulsivity and novelty seeking. This study investigated the effects of cocaine and cannabis on behavioural and event-related potential (ERP) correlates of response inhibition in 38 healthy drug using volunteers. A double-blind placebo-controlled randomized three-way crossover design was used. All subjects completed a standard Go/NoGo task after administration of the drugs. Compared with a placebo, cocaine yielded improved accuracy, quicker reaction times and an increased prefrontal NoGo-P3 ERP. Cannabis produced opposing results; slower reaction times, impaired accuracy and a reduction in the amplitude of the prefrontal NoGo-P3. Cannabis in addition decreased the amplitude of the parietally recorded P3, while cocaine did not affect this. Neither drugs specifically affected the N2 component, suggesting that pre-motor response inhibitory processes remain unaffected. Neither trait impulsivity nor novelty seeking interacted with drug-induced effects on measures of response inhibition. We conclude that acute drug effects on response inhibition seem to be specific to the later, evaluative stages of response inhibition. The acute effects of cannabis appeared less specific to response inhibition than those of cocaine. Together, the results show that the behavioural effects on response inhibition are reflected in electrophysiological correlates. This study did not support a substantial role of vulnerability personality traits in the acute intoxication stage.

Cannabis and alcohol use, affect and impulsivity in psychiatric out-patients' daily lives

BACKGROUND AND AIMS

Cannabis and alcohol are the most commonly used (il)licit drugs world-wide. We compared the effects of cannabis and alcohol use on within-person changes in impulsivity, hostility and positive affect at the momentary and daily levels, as they occurred in daily life.

DESIGN

Observational study involving ecological momentary assessments collected via electronic diaries six random times a day for 28 consecutive days.

SETTING

Out-patients' everyday life contexts in Columbia, MO, USA.

PARTICIPANTS

Ninety-three adult psychiatric out-patients (85% female; mean = 30.9 years old) with borderline personality or depressive disorders, who reported using only cannabis (n = 3), only alcohol (n = 58) or both (n = 32) at least once during the study period.

MEASUREMENTS

Real-time, standard self-report measures of impulsivity, hostility and positive affect, as impacted by momentary reports of cannabis and alcohol use.

FINDINGS

Cannabis use was associated with elevated feelings of impulsivity at the day level [b = 0.83, 95% confidence interval (CI) = 0.17-1.49] and increased hostility at the momentary (b = 0.07, 95% CI = 0.01-0.12) and person (b = 0.81, 95% CI = 0.15-1.47) level. Alcohol use was associated with elevated feelings of impulsivity at the momentary (b = 0.42, 95% CI = 0.13-0.71) and day levels (b = 0.82, 95% CI = 0.22-1.41) and increased positive affect at the momentary (b = 0.12, 95% CI = 0.06-0.18) and day (b = 0.33, 95% CI = 0.16-0.49) levels.

CONCLUSIONS

Cannabis and alcohol use are associated with increases in impulsivity (both), hostility (cannabis) and positive affect (alcohol) in daily life, and these effects are part of separate processes that operate on different time-scales (i.e. momentary versus daily).

Attentional dysfunction in abstinent long-term cannabis users with and without schizophrenia

Long-term cannabis use may confer cognitive deficits and increased risk of psychosis. However, the relationship between cannabis use and schizophrenia is complex. In particular, little is known about the effects of chronic cannabis use on the attention-related electric brain response in schizophrenia. We investigated auditory novelty and oddball P300 evoked potentials in a mixed sample of first-episode and chronic schizophrenic patients and healthy controls with (SZCA, n = 20; COCA, n = 20, abstinence ≥28 days) or without (SZ, n = 20; CO, n = 20) chronic cannabis use. Duration of regular cannabis use was 8.3 ± 5.6 (SZCA) and 9.1 ± 7.1 (COCA) years. In general, schizophrenic patients showed reduced P300 amplitudes. Cannabis use was associated with both a reduced early and late left-hemispheric novelty P300. There was a significant 'diagnosis × cannabis' interaction for the left-hemispheric late novelty P300 in that cannabis use was associated with a reduced amplitude in the otherwise healthy but not in the schizophrenic group compared with their relative control groups (corrected p < 0.02; p > 0.9, respectively). The left-hemispheric late novelty P300 in the otherwise healthy cannabis group correlated inversely with amount and duration of cannabis use (r = -0.50, p = 0.024; r = -0.57, p = 0.009, respectively). Our study confirms attentional deficits with chronic cannabis use. However, cannabis use may lead to different cognitive sequelae in patients with schizophrenia and in healthy controls, possibly reflecting preexisting alterations in the endocannabinoid system in schizophrenia.

Drug Recognition Expert (DRE) examination characteristics of cannabis impairment

BACKGROUND

The Drug Evaluation and Classification Program (DECP) is commonly utilized in driving under the influence (DUI) cases to help determine category(ies) of impairing drug(s) present in drivers. Cannabis, one of the categories, is associated with approximately doubled crash risk. Our objective was to determine the most reliable DECP metrics for identifying cannabis-driving impairment.

METHODS

We evaluated 302 toxicologically-confirmed (blood Δ(9)-tetrahydrocannabinol [THC] ≥1μg/L) cannabis-only DECP cases, wherein examiners successfully identified cannabis, compared to normative data (302 non-impaired individuals). Physiological measures, pupil size/light reaction, and performance on psychophysical tests (one leg stand [OLS], walk and turn [WAT], finger to nose [FTN], Modified Romberg Balance [MRB]) were included.

RESULTS

Cases significantly differed from controls (p<0.05) in pulse (increased), systolic blood pressure (elevated), and pupil size (dilated). Blood collection time after arrest significantly decreased THC concentrations; no significant differences were detected between cases with blood THC <5μg/L versus ≥5μg/L. The FTN best predicted cannabis impairment (sensitivity, specificity, positive/negative predictive value, and efficiency ≥87.1%) utilizing ≥3 misses as the deciding criterion; MRB eyelid tremors produced ≥86.1% for all diagnostic characteristics. Other strong indicators included OLS sway, ≥2 WAT clues, and pupil rebound dilation. Requiring ≥2/4 of: ≥3 FTN misses, MRB eyelid tremors, ≥2 OLS clues, and/or ≥2 WAT clues produced the best results (all characteristics ≥96.7%).

CONCLUSIONS

Blood specimens should be collected as early as possible. The frequently-debated 5μg/L blood THC per se cutoff showed limited relevance. Combined observations on psychophysical and eye exams produced the best cannabis-impairment indicators.

Cannabis and tolerance: acute drug impairment as a function of cannabis use history

Cannabis use history as predictor of neurocognitive response to cannabis intoxication remains subject to scientific and policy debates. The present study assessed the influence of cannabis on neurocognition in cannabis users whose cannabis use history ranged from infrequent to daily use. Drug users (N = 122) received acute doses of cannabis (300 μg/kg THC), cocaine HCl (300 mg) and placebo. Cocaine served as active control for demonstrating neurocognitive test sensitivity. Executive function, impulse control, attention, psychomotor function and subjective intoxication were significantly worse after cannabis administration relative to placebo. Cocaine improved psychomotor function and attention, impaired impulse control and increased feelings of intoxication. Acute effects of cannabis and cocaine on neurocognitive performance were similar across cannabis users irrespective of their cannabis use history. Absence of tolerance implies that that frequent cannabis use and intoxication can be expected to interfere with neurocognitive performance in many daily environments such as school, work or traffic.

Occipital event-related potentials to addiction-related stimuli in detoxified patients with alcohol dependence, and their association with three-month relapse

BACKGROUND

Understanding the biological underpinnings of relapse in alcohol dependency is a major issue in addiction research. Based on recent evidence regarding the relevance of occipital visual evoked response potentials (ERPs) in addiction research, and its significance for relapse research, we assessed occipital ERPs to alcohol- and non-alcohol-related stimuli in recently detoxified patients and controls.

METHODS

Thirty recently detoxified patients with alcohol addiction, and 31 healthy control subjects, were assessed in a Go and a NoGo condition, each using three visual stimuli: tea, juice and beer. In the "Go" condition, subjects had to respond to the juice (12.5 %) and the beer stimulus (12.5 %), and ignore the tea picture (75 %). In the "NoGo" condition, subjects had to respond to the tea picture (75 %) and ignore the juice and the beer picture (12.5 % each). The subjects' EEGs were analyzed with regard to the occipital P100 and N170 ERP components. Patients were then evaluated for relapse 3 months after this initial assessment.

RESULTS

P100 amplitudes differed between conditions and between stimuli, and we found a condition x electrode interaction. However, none of these P100 results involved group or relapse-status effects. N170 amplitudes in patients were elevated as compared to controls. Additionally, patients' heightened N170 amplitudes in response to the alcohol-related (beer) stimulus were found only under the NoGo condition, where subjects had to react to the frequent tea stimulus and ignore the beer and the juice stimuli, thus resulting in a condition x stimulus x group interaction. Patients reporting relapse in a 3-month follow-up assessment showed larger NoGo N170 alcohol cue-related ERP amplitudes and increased depression scores as compared to patients who stayed abstinent. Depression was related to shortened P100 latencies in patients, but unrelated to the N170 NoGo cue-reactivity effect.

CONCLUSIONS

Our results indicate a sensitivity of occipital ERPs to addiction-related stimuli when these act as non-targets. Recently detoxified patients may be vulnerable to addiction-related cues when these occur outside the focus of directed attention, thereby circumventing intentional control processes. Furthermore, ERPs to addiction-related stimuli may be useful as a predictor of abstinence success in recently detoxified patients.

An Event-Related Potential Study on the Effects of Cannabis on Emotion Processing

The effect of cannabis on emotional processing was investigated using event-related potential paradigms (ERPs). ERPs associated with emotional processing of cannabis users, and non-using controls, were recorded and compared during an implicit and explicit emotional expression recognition and empathy task. Comparisons in P3 component mean amplitudes were made between cannabis users and controls. Results showed a significant decrease in the P3 amplitude in cannabis users compared to controls. Specifically, cannabis users showed reduced P3 amplitudes for implicit compared to explicit processing over centro-parietal sites which reversed, and was enhanced, at fronto-central sites. Cannabis users also showed a decreased P3 to happy faces, with an increase to angry faces, compared to controls. These effects appear to increase with those participants that self-reported the highest levels of cannabis consumption. Those cannabis users with the greatest consumption rates showed the largest P3 deficits for explicit processing and negative emotions. These data suggest that there is a complex relationship between cannabis consumption and emotion processing that appears to be modulated by attention.

Dose-dependent effects of cannabis on the neural correlates of error monitoring in frequent cannabis users

Cannabis has been suggested to impair the capacity to recognize discrepancies between expected and executed actions. However, there is a lack of conclusive evidence regarding the acute impact of cannabis on the neural correlates of error monitoring. In order to contribute to the available knowledge, we used a randomized, double-blind, between-groups design to investigate the impact of administration of a low (5.5 mg THC) or high (22 mg THC) dose of vaporized cannabis vs. placebo on the amplitudes of the error-related negativity (ERN) and error positivity (Pe) in the context of the Flanker task, in a group of frequent cannabis users (required to use cannabis minimally 4 times a week, for at least 2 years). Subjects in the high dose group (n=18) demonstrated a significantly diminished ERN in comparison to the placebo condition (n=19), whereas a reduced Pe amplitude was observed in both the high and low dose (n=18) conditions, as compared to placebo. The results suggest that a high dose of cannabis may affect the neural correlates of both the conscious (late), as well as the initial automatic processes involved in error monitoring, while a low dose of cannabis might impact only the conscious (late) processing of errors.

Smoked cannabis' psychomotor and neurocognitive effects in occasional and frequent smokers

Δ9-Tetrahydrocannabinol (THC), the primary psychoactive constituent in cannabis, impairs psychomotor performance, cognition and driving ability; thus, driving under the influence of cannabis is a public safety concern. We documented cannabis' psychomotor, neurocognitive, subjective and physiological effects in occasional and frequent smokers to investigate potential differences between these smokers. Fourteen frequent (≥4x/week) and 11 occasional (<2x/week) cannabis smokers entered a secure research unit ∼19 h prior to smoking one 6.8% THC cigarette. Cognitive and psychomotor performance was evaluated with the critical tracking (CTT), divided attention (DAT), n-back (working memory) and Balloon Analog Risk (BART) (risk-taking) tasks at -1.75, 1.5, 3.5, 5.5 and 22.5 h after starting smoking. GLM (General Linear Model) repeated measures ANOVA was utilized to compare scores. Occasional smokers had significantly more difficulty compensating for CTT tracking error compared with frequent smokers 1.5 h after smoking. Divided attention performance declined significantly especially in occasional smokers, with session × group effects for tracking error, hits, false alarms and reaction time. Cannabis smoking did not elicit session × group effects on the n-back or BART. Controlled cannabis smoking impaired psychomotor function, more so in occasional smokers, suggesting some tolerance to psychomotor impairment in frequent users. These data have implications for cannabis-associated impairment in driving under the influence of cannabis cases.

Medical marijuana for cancer

Answer questions and earn CME/CNE Marijuana has been used for centuries, and interest in its medicinal properties has been increasing in recent years. Investigations into these medicinal properties has led to the development of cannabinoid pharmaceuticals such as dronabinol, nabilone, and nabiximols. Dronabinol is best studied in the treatment of nausea secondary to cancer chemotherapy and anorexia associated with weight loss in patients with acquired immune deficiency syndrome, and is approved by the US Food and Drug Administration for those indications. Nabilone has been best studied for the treatment of nausea secondary to cancer chemotherapy. There are also limited studies of these drugs for other conditions. Nabiximols is only available in the United States through clinical trials, but is used in Canada and the United Kingdom for the treatment of spasticity secondary to multiple sclerosis and pain. Studies of marijuana have concentrated on nausea, appetite, and pain. This article will review the literature regarding the medical use of marijuana and these cannabinoid pharmaceuticals (with emphasis on indications relevant to oncology), as well as available information regarding adverse effects of marijuana use.

Effects of marijuana use on impulsivity and hostility in daily life

BACKGROUND

Marijuana use is increasingly prevalent among young adults. While research has found adverse effects associated with marijuana use within experimentally controlled laboratory settings, it is unclear how recreational marijuana use affects day-to-day experiences in users. The present study sought to examine the effects of marijuana use on within-person changes in impulsivity and interpersonal hostility in daily life using smartphone administered assessments.

METHODS

Forty-three participants with no substance dependence reported on their alcohol consumption, tobacco use, recreational marijuana use, impulsivity, and interpersonal hostility over the course of 14 days. Responses were analyzed using multilevel modeling.

RESULTS

Marijuana use was associated with increased impulsivity on the same day and the following day relative to days when marijuana was not used, independent of alcohol use. Marijuana was also associated with increased hostile behaviors and perceptions of hostility in others on the same day when compared to days when marijuana was not used. These effects were independent of frequency of marijuana use or alcohol use. There were no significant effects of alcohol consumption on impulsivity or interpersonal hostility.

CONCLUSIONS

Marijuana use is associated with changes in impulse control and hostility in daily life. This may be one route by which deleterious effects of marijuana are observed for mental health and psychosocial functioning. Given the increasing prevalence of recreational marijuana use and the potential legalization in some states, further research on the potential consequences of marijuana use in young adults' day-to-day life is warranted.

Effects of cannabis on impulsivity: a systematic review of neuroimaging findings

We conducted a systematic review to assess the evidence for specific effects of cannabis on impulsivity, disinhibition and motor control. The review had a specific focus on neuroimaging findings associated with acute and chronic use of the drug and covers literature published up until May 2012. Seventeen studies were identified, of which 13 met the inclusion criteria; three studies investigated acute effects of cannabis (1 fMRI, 2 PET), while six studies investigated non-acute functional effects (4 fMRI, 2 PET), and four studies investigated structural alterations. Functional imaging studies of impulsivity studies suggest that prefrontal blood flow is lower in chronic cannabis users than in controls. Studies of acute administration of THC or marijuana report increased brain metabolism in several brain regions during impulsivity tasks. Structural imaging studies of cannabis users found differences in reduced prefrontal volumes and white matter integrity that might mediate the abnormal impulsivity and mood observed in marijuana users. To address the question whether impulsivity as a trait precedes cannabis consumption or whether cannabis aggravates impulsivity and discontinuation of usage more longitudinal study designs are warranted.

Cannabis and creativity: highly potent cannabis impairs divergent thinking in regular cannabis users

RATIONALE

Cannabis users often claim that cannabis has the potential to enhance their creativity. Research suggests that aspects of creative performance might be improved when intoxicated with cannabis; however, the evidence is not conclusive.

OBJECTIVE

The aim of this study was to investigate the acute effects of cannabis on creativity.

METHODS

We examined the effects of administering a low (5.5 mg delta-9-tetrahydrocannabinol [THC]) or high (22 mg THC) dose of vaporized cannabis vs. placebo on creativity tasks tapping into divergent (Alternate Uses Task) and convergent (Remote Associates Task) thinking, in a population of regular cannabis users. The study used a randomized, double-blind, between-groups design.

RESULTS

Participants in the high-dose group (n = 18) displayed significantly worse performance on the divergent thinking task, compared to individuals in both the low-dose (n = 18) and placebo (n = 18) groups.

CONCLUSIONS

The findings suggest that cannabis with low potency does not have any impact on creativity, while highly potent cannabis actually impairs divergent thinking.

Deficits in behavioural inhibition in substance abuse and addiction: a meta-analysis

AIMS

Deficits in behavioural inhibitory control are attracting increasing attention as a factor behind the development and maintenance of substance dependence. However, evidence for such a deficit is varied in the literature. Here, we synthesised published results to determine whether inhibitory ability is reliably impaired in substance users compared to controls.

METHODS

The meta-analysis used fixed-effects models to integrate results from 97 studies that compared groups with heavy substance use or addiction-like behaviours with healthy control participants on two experimental paradigms commonly used to assess response inhibition: the Go/NoGo task, and the Stop-Signal Task (SST). The primary measures of interest were commission errors to NoGo stimuli and stop-signal reaction time in the SST. Additionally, we examined omission errors to Go stimuli, and reaction time in both tasks. Because inhibition is more difficult when inhibition is required infrequently, we considered papers with rare and equiprobable NoGo stimuli separately.

RESULTS

Inhibitory deficits were apparent for heavy use/dependence on cocaine, MDMA, methamphetamine, tobacco, and alcohol (and, to a lesser extent, non-dependent heavy drinkers), and in pathological gamblers. On the other hand, no evidence for an inhibitory deficit was observed for opioids or cannabis, and contradictory evidence was observed for internet addiction.

CONCLUSIONS

The results are generally consistent with the view that substance use disorders and addiction-like behavioural disorders are associated with impairments in inhibitory control. Implications for treatment of substance use are discussed, along with suggestions for future research arising from the limitations of the extant literature.

Cannabis use and neurocognitive functioning in a non-clinical sample of users

OBJECTIVE

With the recent debates over marijuana legalization and increases in use, it is critical to examine its role in cognition. While many studies generally support the adverse acute effects of cannabis on neurocognition, the non-acute effects remain less clear. The current study used a cross-sectional design to examine relationships between recent and past cannabis use on neurocognitive functioning in a non-clinical adult sample.

METHOD

One hundred and fifty-eight participants were recruited through fliers distributed around local college campuses and the community. All participants completed the Brief Drug Use History Form, the Structured Clinical Interview for DSM-IV Disorders, and neurocognitive assessment, and underwent urine toxicology screening. Participants consisted of recent users (n=68), past users (n=41), and non-users (n=49).

RESULTS

Recent users demonstrated significantly (p<.05) worse performance than non-users across cognitive domains of attention/working memory (M=42.4, SD=16.1 vs. M=50.5, SD=10.2), information processing speed (M=44.3, SD=7.3 vs. M=52.1, SD=11.0), and executive functioning (M=43.6, SD=13.4 vs. M=48.6, SD=7.2). There were no statistically significant differences between recent users and past users on neurocognitive performance. Frequency of cannabis use in the last 4 weeks was negatively associated with global neurocognitive performance and all individual cognitive domains. Similarly, amount of daily cannabis use was negatively associated with global neurocognitive performance and individual cognitive domains.

CONCLUSIONS

Our results support the widespread adverse effects of cannabis use on neurocognitive functioning. Although some of these adverse effects appear to attenuate with abstinence, past users' neurocognitive functioning was consistently lower than non-users.

Event-related potentials in substance use disorders: a narrative review based on articles from 1984 to 2012

Mechanisms that mediate the transition from occasional, controlled, drug use to the impaired control that characterizes severe dependence are still a matter of investigation. The etiology of substance use disorders (SUDs) is complex, and in this context of complexity, the concept of "endophenotype," has gained extensive popularity in recent years. The main aim of endophenotypes is to provide a simpler, more proximal target to discover the biological underpinnings of a psychiatric syndrome. In this view, neurocognitive and neurophysiological impairments that suggest functional impairments associated with SUDs have been proposed as possible endophenotypes. Because of its large amplitude and relatively easy elicitation, the most studied of the cognitive brain event-related potentials (ERPs), the P300 component, has been proposed as one possible candidate. However, if a P300 amplitude alteration is a common finding in SUDs, it is also observable in other psychiatric afflictions, suggesting that the associations found may just reflect a common measure of brain dysfunction. On this basis, it has been proposed that a multivariate endophenotype, based on a weighted combination of electrophysiological features, may provide greater diagnostic classification power than any single endophenotype. The rationale for investigating multiple features is to show that combining them provides extra useful information that is not available in the individual features, leading ultimately to a multivariate phenotype.The aim of the present article is to outline the potential usefulness of this kind of "combined electrophysiological procedure" applied to SUDs. We present a review of ERP studies, combining data from people with SUD, family members, and normal control subjects, to verify whether the combination of 4ERPs (P50, MMN, P300, and N400) may produce profiles of cortical anomalies induced by different types of SUD (alcohol vs cocaine vs cannabis vs heroin).