Neurophysiological and subjective profile of marijuana with varying concentrations of cannabinoids

A critical assessment of the abuse, dependence and associated safety risks of naturally occurring and synthetic cannabinoids

Various countries and US States have legalized cannabis, and the use of the psychoactive1 and non-psychoactive cannabinoids is steadily increasing. In this review, we have collated evidence from published non-clinical and clinical sources to evaluate the abuse, dependence and associated safety risks of the individual cannabinoids present in cannabis. As context, we also evaluated various synthetic cannabinoids. The evidence shows that delta-9 tetrahydrocannabinol (Δ9-THC) and other psychoactive cannabinoids in cannabis have moderate reinforcing effects. Although they rapidly induce pharmacological tolerance, the withdrawal syndrome produced by the psychoactive cannabinoids in cannabis is of moderate severity and lasts from 2 to 6 days. The evidence overwhelmingly shows that non-psychoactive cannabinoids do not produce intoxicating, cognitive or rewarding properties in humans. There has been much speculation whether cannabidiol (CBD) influences the psychoactive and potentially harmful effects of Δ9-THC. Although most non-clinical and clinical investigations have shown that CBD does not attenuate the CNS effects of Δ9-THC or synthetic psychoactive cannabinoids, there is sufficient uncertainty to warrant further research. Based on the analysis, our assessment is cannabis has moderate levels of abuse and dependence risk. While the risks and harms are substantially lower than those posed by many illegal and legal substances of abuse, including tobacco and alcohol, they are far from negligible. In contrast, potent synthetic cannabinoid (CB1/CB2) receptor agonists are more reinforcing and highly intoxicating and pose a substantial risk for abuse and harm. 1 "Psychoactive" is defined as a substance that when taken or administered affects mental processes, e.g., perception, consciousness, cognition or mood and emotions.

Vaporized D-limonene selectively mitigates the acute anxiogenic effects of Δ9-tetrahydrocannabinol in healthy adults who intermittently use cannabis

BACKGROUND

Cannabis contains hundreds of chemical constituents beyond delta-9-tetrahydrocannabinol (THC), which is believed to drive most of its acute pharmacodynamic effects. The entourage effect theory asserts that non-THC constituents can impact acute cannabis effects, but few empirical studies have systematically evaluated this theory in humans. This study assessed whether the cannabis terpenoid d-limonene mitigates the acute anxiogenic effects of THC.

METHODS

Twenty healthy adults completed nine, double-blind outpatient sessions in which they inhaled vaporized THC alone (15mg or 30mg), d-limonene alone (1mg or 5mg), the same doses of THC and d-limonene together, or placebo; a subset of participants (n=12) completed a tenth session in which 30mg THC+15mg d-limonene was administered. Outcomes included subjective drug effects, cognitive/psychomotor performance, vital signs, and plasma THC and d-limonene concentrations.

RESULTS

When d-limonene was administered alone, pharmacodynamic outcomes did not differ from placebo. Administration of 15mg and 30mg THC alone produced subjective, cognitive, and physiological effects typical of acute cannabis exposure. Ratings of anxiety-like subjective effects qualitatively decreased as d-limonene dose increased and concurrent administration of 30mg THC+15mg d-limonene significantly reduced ratings of "anxious/nervous" and "paranoid" compared with 30mg THC alone. Other pharmacodynamic effects were unchanged by d-limonene. D-limonene plasma concentrations were dose orderly, and concurrent administration of d-limonene did not alter THC pharmacokinetics.

CONCLUSIONS

D-limonene selectively attenuated THC-induced anxiogenic effects, suggesting this terpenoid could increase the therapeutic index of THC. Future research should determine whether this effect extends to oral dose formulations and evaluate the interactions between other cannabis terpenoids or cannabinoids and THC.

Nabilone Impairs Spatial and Verbal Working Memory in Healthy Volunteers

Background: Memory impairments and psychosis-like experiences can be adverse effects of cannabis use. However, reports on the cognitive impact of cannabis use are not consistent. There are also limited studies on the psychotomimetic effects of cannabinoid compounds to reveal the association between cannabis and psychosis. Therefore, we investigated the effect of acute cannabinoid intoxication on verbal working memory (VWM) and spatial working memory (SWM) following oral doses of the synthetic cannabinoid agonist, nabilone (1-2 mg, oral). We further investigated the effect of nabilone on psychosis-like experiences (schizotypy scores) and associations of schizotypy with VWM and SWM. Methods: Healthy participants (n=28) completed spatial and digit span tasks across different delay conditions (0, 6, 12, and 18 sec) after receiving nabilone (1-2 mg, PO) or placebo in a randomized, double-blind, counterbalanced, crossover manner. A subset of participants completed a short battery of schizotypy measures (n=25). Results: Nabilone impaired VWM (p=0.03, weak effect size η2=0.02) and SWM (p=0.00016, η2=0.08). Nabilone did not significantly change overall schizotypy scores. Schizotypy scores were negatively correlated with working memory (WM) averaged across all delays and both modalities, under placebo (ρ=-0.41, p=0.04). In addition, there were significant negative correlations between occasions of cannabis use and overall WM averaged scores across drug treatments (ρ=-0.49, p=0.007) and under placebo (ρ=-0.45, p=0.004). The results showed that the drug effect in the less frequent cannabis users was more pronounced on the SWM (p<0.01) and VWM (p<0.01), whereas there appeared to be little drug effect in the frequent cannabis users. Conclusion: Low doses of synthetic cannabinoid impaired SWM and VWM, indicating that exogenous activation of the cannabinoid system influences cognitive performance. Further, the results replicated previous findings that schizotypy is correlated with deficits in WM. Clinical Trial Registry Name: Nabilone and caffeine effects on the perceptions of visually, auditory, tactile and multimodal illusions in healthy volunteers. Clinical Trial Registration Number: CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry).

Pharmacokinetics of Oral Minor Cannabinoids in Blood and Brain

Introduction: Minor cannabinoids are increasingly being consumed in oral formulations (i.e., edibles, tinctures) for medical and nonmedical purposes. This study examined the pharmacokinetics (PKs) of cannabinoids tetrahydrocannabivarin (THCV), cannabichromene (CBC), cannabinol (CBN), and delta-8-tetrahydrocannabinol (D8-THC) after the first and last oral dose during a 14-day administration period. Materials and Methods: Sprague-Dawley rats (N=6 animals/dose, 50% female) were given an assigned dose of one of four cannabinoids (THCV=3.2-100 mg/kg, CBC=3.2-100 mg/kg, CBN=1-100 mg/kg, or D8-THC=0.32-10 mg/kg) or vehicle (medium-chain triglyceride oil) through oral gavage once daily for 14 days. Blood was collected 45 min and 1.5, 3, and 24 h following the first dose (day 1) and the last dose (day 14) of repeated oral cannabinoid treatment for PK analysis. Outcomes of interest included time to maximum concentration (Tmax), maximum concentration (Cmax), and area under the concentration versus time curve (AUClast). Dose-normalized (DN) Cmax and DN AUClast were also calculated. Brain tissue was collected 24 h post-administration of the first (day 1) and the last (day 14) dose of each cannabinoid to determine concentrations in brain. Results: All cannabinoids tested were detectable in plasma after single and 14-day repeated dosing. DN Cmax and DN AUClast were highest for D8-THC, followed by CBC, CBN, and THCV. There was no sex difference observed in cannabinoid kinetics. Accumulation of D8-THC in plasma was observed after 14 days of administration. THCV levels in plasma were lower on day 14 compared to day 1, indicating potential adaptation of metabolic pathways and increased drug elimination. Cannabinoids were detected in brain tissue 24 h post-administration of the first and the last dose of 17-100 mg/kg THCV, 3.2-100 mg/kg CBC, 10-100 mg/kg CBN, and 10 mg/kg D8-THC. Conclusions: THCV, CBC, CBN, and D8-THC produced detectable levels in plasma and translocated to brain tissue after the first dose (day 1) and the last dose (day 14) of repeated oral dosing. Examination of PKs of these minor cannabinoids in blood and brain provides a critical step for informing target dose ranges and dosing schedules in future studies that evaluate the potential effects of these compounds.

Women are Taking the Hit: Examining the Unique Consequences of Cannabis Use Across the Female Lifespan

Cannabis use has risen dramatically in recent years due to global decriminalization and a resurgence in the interest of potential therapeutic benefits. While emerging research is shaping our understanding of the benefits and harms of cannabis, there remains a paucity of data specifically focused on how cannabis affects the female population. The female experience of cannabis use is unique, both in the societal context and because of the biological ramifications. This is increasingly important given the rise in cannabis potency, as well as the implications this has for the prevalence of Cannabis Use Disorder (CUD). Therefore, this scoping review aims to discuss the prevalence of cannabis use and CUD in women throughout their lifespan and provide a balanced prospective on the positive and negative consequences of cannabis use. In doing so, this review will highlight the necessity for continued research that goes beyond sex differences.

The Relationship Between Cannabinoids and Neural Oscillations: How Cannabis Disrupts Sensation, Perception, and Cognition

Disruptions in neural oscillations are believed to be one critical mechanism by which cannabinoids, such as delta-9-tetrahyrdrocannabinol (THC; the primary psychoactive constituent of cannabis), perturbs brain function. Here we briefly review the role of synchronized neural activity, particularly in the gamma (30-80 Hz) and theta (4-7 Hz) frequency range, in sensation, perception, and cognition. This is followed by a review of clinical studies utilizing electroencephalography (EEG) which have demonstrated that both chronic and acute cannabinoid exposure disrupts neural oscillations in humans. We also offer a hypothetical framework through which endocannabinoids modulate neural synchrony at the network level. This also includes speculation on how both chronic and acute cannabinoids disrupt functionally relevant neural oscillations by altering the fine tuning of oscillations and the inhibitory/excitatory balance of neural circuits. Finally, we highlight important clinical implications of such oscillatory disruptions, such as the potential relationship between cannabis use, altered neural synchrony, and disruptions in sensation, perception, and cognition, which are perturbed in disorders such as schizophrenia.

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.

Interaction of sex and cannabis in adult in vivo brain imaging studies: A systematic review

Cannabis has been shown to cause structural and functional neurocognitive changes in heavy users. Cannabis use initiation aligns with brain development trajectories; therefore, it is imperative that the potential neurological implications of cannabis use are understood. Males and females reach neurodevelopmental milestones at different rates making it necessary to consider biological sex in all cannabis and brain-based research. Through use of a systamatic review in accordance with PRISMA guidelines, we aimed to understand the interaction between biological sex and cannabis use on brain-based markers. In total, 18 articles containing a sex-based analysis of cannabis users were identified. While the majority of studies (n = 11) reported no sex by cannabis use interactions on brain-based markers, those that reported findings (n = 8) suggest females may be more susceptible to cannabis’ neurotoxic effects. Unfortunately, a large portion of the literature was excluded due to no sex-based analysis. In addition, studies that reported no sex differences often contained a reduced number of females which may result in some studies being underpowered for sex-based analyses, making it difficult to draw firm conclusions. Suggestions to improve cannabis and sex-based reseach are proposed.

Synthetic cannabinoid JWH-073 alters both acute behavior and in vivo/vitro electrophysiological responses in mice

JWH-073 is a synthetic cannabinoid (SCB) that is illegally marketed within an "herbal blend", causing psychoactive effects more intense than those produced by Cannabis. Users report that JWH-073 causes less harmful effects than other SCBs, misrepresenting it as a "safe JWH-018 alternative", which in turn prompts its recreational use. The present study is aimed to investigate the in vivo pharmacological activity on physiological and neurobehavioral parameters in male CD-1 mice after acute 1 mg/kg JWH-073 administration. To this aim we investigate its effect on sensorimotor (visual, acoustic, and tactile), motor (spontaneous motor activity and catalepsy), and memory functions (novel object recognition; NOR) in mice coupling behavioral and EEG data. Moreover, to clarify how memory function is affected by JWH-073, we performed in vitro electrophysiological studies in hippocampal preparations using a Long-Term Potentiation (LTP) stimulation paradigm. We demonstrated that acute administration of JWH-073 transiently decreased motor activity for up to 25 min and visual sensorimotor responses for up to 105 min, with the highest effects at 25 min (~48 and ~38%, respectively), while the memory function was altered up to 24 h (~33%) in treated-mice as compared to the vehicle. EEG in the somatosensory cortex showed a maximal decrease of α (~23%) and γ (~26%) bands at 15 min, β (~26%) band at 25 min, a maximal increase of θ (~14%) band at 25 min and δ (~35%) band at 2 h, and a significant decrease of θ (~18%), α (~26%), and β (~10%) bands during 24 h. On the other hand, EEG in the hippocampus showed a significant decrease of all bands from 10 min to 2 h, with the maximal effect at 30 min for θ (~34%) and γ (~26%) bands and 2 h for α (~36%), β (~29%), and δ (~15%) bands. Notably, the δ band significant increase both at 5 min (~12%) and 24 h (~19%). Moreover, in vitro results support cognitive function impairment (~60% of decrease) by interfering with hippocampal synaptic transmission and LTP generation. Our results suggest that JWH-073 deeply alters brain electrical responsiveness with minor behavioral symptoms. Thus, it poses a subtle threat to consumers who mistakenly consider it safer than other SCBs.

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

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

Endocannabinoids, cannabinoids and the regulation of anxiety

Cannabis has been used for hundreds of years, with its ability to dampen feelings of anxiety often reported as a primary reason for use. Only recently has the specific role cannabinoids play in anxiety been thoroughly investigated. Here we discuss the body of evidence describing how endocannabinoids and exogenous cannabinoids are capable of regulating the generation and termination of anxiety states. Disruption of the endogenous cannabinoid (eCB) system following genetic manipulation, pharmacological intervention or stress exposure reliably leads to the generation of an anxiety state. On the other hand, upregulation of eCB signaling is capable of alleviating anxiety-like behaviors in multiple paradigms. When considering exogenous cannabinoid administration, cannabinoid receptor 1 (CB1) agonists have a biphasic, dose-dependent effect on anxiety such that low doses are anxiolytic while high doses are anxiogenic, a phenomenon that is evident in both rodent models and humans. Translational studies investigating a loss of function mutation in the gene for fatty acid amide hydrolase, the enzyme responsible for metabolizing AEA, have also shown that AEA signaling regulates anxiety in humans. Taken together, evidence reviewed here has outlined a convincing argument for cannabinoids being powerful regulators of both the manifestation and amelioration of anxiety symptoms, and highlights the therapeutic potential of targeting the eCB system for the development of novel classes of anxiolytics. This article is part of the special issue on 'Cannabinoids'.

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

BACKGROUND

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

METHODS

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

RESULTS

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

DISCUSSION

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

Cannabidiol normalizes resting-state functional connectivity in treatment-resistant epilepsy

OBJECTIVE

Resting-state (rs) network dysfunction is a contributing factor to treatment resistance in epilepsy. In treatment-resistant epilepsy (TRE), pharmacological and nonpharmacological therapies have been shown to improve such dysfunction. In this study, our goal was to prospectively evaluate the effect of highly purified plant-derived cannabidiol (CBD; Epidiolex®) on rs functional magnetic resonance imaging (fMRI) functional connectivity (rs-FC). We hypothesized that CBD would change and potentially normalize the rs-FC in TRE.

METHODS

Twenty-two of 27 participants with TRE completed all study procedures including longitudinal pre-/on-CBD rs-fMRI (8M/14F, mean age = 36.2 ± 15.9 years, TRE duration = 18.3 ± 12.6 years); there were no differences in age (p = 0.99) or sex (p = 0.15) between groups. Assessments collected included seizure frequency (SF), Chalfont Seizure Severity Scale (CSSS), Columbia Suicide Severity Rating Scale (C-SSRS), Adverse Events Profile (AEP), and Profile of Mood States (POMS). Twenty-three healthy controls (HCs) received rs-fMRI and POMS once.

RESULTS

Participants with TRE showed average decrease of 71.7% in SF (p < 0.0001) and improved CSSS, AEP, and POMS confusion, depression, and fatigue subscores (all p < 0.05) on-CBD with POMS scores becoming similar to those of HCs. Paired t-tests showed significant pre-/on-CBD changes in rs-FC in cerebellum, frontal areas, temporal areas, hippocampus, and amygdala with some of them correlating with improvement in behavioral measures. Significant differences in rs-FC between pre-CBD and HCs were found in cerebellum, frontal, and occipital regions. After controlling for changes in SF with CBD, these differences were no longer present when comparing on-CBD to HCs.

SIGNIFICANCE

This study indicates that highly purified CBD modulates and potentially normalizes rs-FC in the epileptic brain. This effect may underlie its efficacy. This study provides Class III evidence for CBD's normalizing effect on rs-FC in TRE.

Effects of ∆9-tetrahydrocannabinol on aversive memories and anxiety: a review from human studies

BACKGROUND

Posttraumatic stress disorder (PTSD) may stem from the formation of aberrant and enduring aversive memories. Some PTSD patients have recreationally used Cannabis, probably aiming at relieving their symptomatology. However, it is still largely unknown whether and how Cannabis or its psychotomimetic compound Δ⁹-tetrahydrocannabinol (THC) attenuates the aversive/traumatic memory outcomes. Here, we seek to review and discuss the effects of THC on aversive memory extinction and anxiety in healthy humans and PTSD patients.

METHODS

Medline, PubMed, Cochrane Library, and Central Register for Controlled Trials databases were searched to identify peer-reviewed published studies and randomized controlled trials in humans published in English between 1974 and July 2020, including those using only THC and THC combined with cannabidiol (CBD). The effect size of the experimental intervention under investigation was calculated.

RESULTS

At low doses, THC can enhance the extinction rate and reduce anxiety responses. Both effects involve the activation of cannabinoid type-1 receptors in discrete components of the corticolimbic circuitry, which could couterbalance the low "endocannabinoid tonus" reported in PTSD patients. The advantage of associating CBD with THC to attenuate anxiety while minimizing the potential psychotic or anxiogenic effect produced by high doses of THC has been reported. The effects of THC either alone or combined with CBD on aversive memory reconsolidation, however, are still unknown.

CONCLUSIONS

Current evidence from healthy humans and PTSD patients supports the THC value to suppress anxiety and aversive memory expression without producing significant adverse effects if used in low doses or when associated with CBD. Future studies are guaranteed to address open questions related to their dose ratios, administration routes, pharmacokinetic interactions, sex-dependent differences, and prolonged efficacy.

Receptors and Channels Possibly Mediating the Effects of Phytocannabinoids on Seizures and Epilepsy

Epilepsy contributes to approximately 1% of the global disease burden. By affecting especially young children as well as older persons of all social and racial variety, epilepsy is a present disorder worldwide. Currently, only 65% of epileptic patients can be successfully treated with antiepileptic drugs. For this reason, alternative medicine receives more attention. Cannabis has been cultivated for over 6000 years to treat pain and insomnia and used since the 19th century to suppress epileptic seizures. The two best described phytocannabinoids, (−)-trans-Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD) are claimed to have positive effects on different neurological as well as neurodegenerative diseases, including epilepsy. There are different cannabinoids which act through different types of receptors and channels, including the cannabinoid receptor 1 and 2 (CB₁, CB₂), G protein-coupled receptor 55 (GPR55) and 18 (GPR18), opioid receptor µ and δ, transient receptor potential vanilloid type 1 (TRPV1) and 2 (TRPV2), type A γ-aminobutyric acid receptor (GABA_AR) and voltage-gated sodium channels (VGSC). The mechanisms and importance of the interaction between phytocannabinoids and their different sites of action regarding epileptic seizures and their clinical value are described in this review.

Barriers to the wider adoption of medicinal Cannabis

The use of Cannabis-based preparations for medicinal use has waxed and waned in the multi-millennial history of human co-existence with the plant and its cultivation. Recorded use of preparations from Cannabis is effectively as old as recorded history with examples from China, India and Ancient Egypt. Prohibition and restriction of availability allowed a number of alternatives to take the place of Cannabis preparations. However, there has been a worldwide resurgence in medicinal Cannabis advocacy from the public. Media interest has been piqued by particular evocative cases. Altogether, therefore, there is pressure on healthcare professionals to prescribe and dispense Cannabis-based preparations. This review enunciates some of the barriers which are slowing the wider adoption of medicinal Cannabis.

Effects of Cannabidiol and Delta-9-Tetrahydrocannabinol on Emotion, Cognition, and Attention: A Double-Blind, Placebo-Controlled, Randomized Experimental Trial in Healthy Volunteers

The two main phytocannabinoids-delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD)-have been extensively studied, and it has been shown that THC can induce transient psychosis. At the same time, CBD appears to have no psychotomimetic potential. On the contrary, emerging evidence for CBD's antipsychotic properties suggests that it may attenuate effects induced by THC. Thus, we investigated and compared the effects of THC and CBD administration on emotion, cognition, and attention as well as the impact of CBD pre-treatment on THC effects in healthy volunteers. We performed a placebo-controlled, double-blind, experimental trial (GEI-TCP II; ClinicalTrials.gov identifier: NCT02487381) with 60 healthy volunteers randomly allocated to four parallel intervention groups, receiving either placebo, 800 mg CBD, 20 mg THC, or both cannabinoids. Subjects underwent neuropsychological tests assessing working memory (Letter Number Sequencing test), cognitive processing speed (Digit Symbol Coding task), attention (d2 Test of Attention), and emotional state (adjective mood rating scale [EWL]). Administration of CBD alone did not influence the emotional state, cognitive performance, and attention. At the same time, THC affected two of six emotional categories-more precisely, the performance-related activity and extraversion-, reduced the cognitive processing speed and impaired the performance on the d2 Test of Attention. Interestingly, pre-treatment with CBD did not attenuate the effects induced by THC. These findings show that the acute intake of CBD itself has no effect per se in healthy volunteers and that a single dose of CBD prior to THC administration was insufficient to mitigate the detrimental impact of THC in the given setting. This is in support of a complex interaction between CBD and THC whose effects are not counterbalanced by CBD under all circumstances.

Changing landscape of cannabis: novel products, formulations, and methods of administration

Laws regulating cannabis have changed radically in the U.S. and abroad. Historically, users smoked dried cannabis flowers that contained Δ9-tetrahydrocannabinol (THC), the primary psychoactive component of cannabis, as the principal product constituent. Coincident with cannabis legalization and increased interest in medicinal use of the plant, there is now an expansive retail cannabis marketplace with novel cannabis products, formulations, and methods of administration. In this review, we describe emergent cannabis product chemotypes (e.g. THC-dominant, CBD-dominant, balanced or 'hybrid' with high concentrations of THC and CBD), product formulations (e.g. edibles, concentrates), and methods of administration (e.g. smoked, vaporized, orally ingested). Psychologists can play a pivotal role in studying the health impact of cannabis legalization and conducting research to inform product regulation.

Cannabichromene is a cannabinoid CB2 receptor agonist

BACKGROUND AND PURPOSE

Cannabichromene (CBC) is one of the most abundant phytocannabinoids in Cannabis spp. It has modest antinociceptive and anti-inflammatory effects and potentiates some effects of Δ⁹ -tetrahydrocannabinol in vivo. How CBC exerts these effects is poorly defined and there is little information about its efficacy at cannabinoid receptors. We sought to determine the functional activity of CBC at cannabinoid CB₁ and CB₂ receptors.

EXPERIMENTAL APPROACH

AtT20 cells stably expressing haemagglutinin-tagged human CB₁ and CB₂ receptors were used. Assays of cellular membrane potential and loss of cell surface receptors were performed.

KEY RESULTS

CBC activated CB₂ but not CB₁ receptors to produce hyperpolarization of AtT20 cells. This activation was inhibited by a CB₂ receptor antagonist AM630, and sensitive to Pertussis toxin. Application of CBC reduced activation of CB₂ , but not CB₁ , receptors by subsequent co-application of CP55,940, an efficacious CB₁ and CB₂ receptor agonist. Continuous CBC application induced loss of cell surface CB₂ receptors and desensitization of the CB₂ receptor-induced hyperpolarization.

CONCLUSIONS AND IMPLICATIONS

CBC is a selective CB₂ receptor agonist displaying higher efficacy than tetrahydrocannabinol in hyperpolarizing AtT20 cells. CBC can also recruit CB₂ receptor regulatory mechanisms. CBC may contribute to the potential therapeutic effectiveness of some cannabis preparations, potentially through CB₂ receptor-mediated modulation of inflammation.

Absence of Entourage: Terpenoids Commonly Found in Cannabis sativa Do Not Modulate the Functional Activity of Δ9-THC at Human CB1 and CB2 Receptors

Introduction: Compounds present in Cannabis sativa such as phytocannabinoids and terpenoids may act in concert to elicit therapeutic effects. Cannabinoids such as Δ9-tetrahydrocannabinol (Δ9-THC) directly activate cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2); however, it is not known if terpenoids present in Cannabis also affect cannabinoid receptor signaling. Therefore, we examined six common terpenoids alone, and in combination with cannabinoid receptor agonists, on CB1 and CB2 signaling in vitro. Materials and Methods: Potassium channel activity in AtT20 FlpIn cells transfected with human CB1 or CB2 receptors was measured in real time using FLIPR® membrane potential dye in a FlexStation 3 plate reader. Terpenoids were tested individually and in combination for periods up to 30 min. Endogenous somatostatin receptors served as a control for direct effects of drugs on potassium channels. Results: α-Pinene, β-pinene, β-caryophyllene, linalool, limonene, and β-myrcene (up to 30-100 μM) did not change membrane potential in AtT20 cells expressing CB1 or CB2, or affect the response to a maximally effective concentration of the synthetic cannabinoid CP55,940. The presence of individual or a combination of terpenoids did not affect the hyperpolarization produced by Δ9-THC (10 μM): (CB1: control, 59%±7%; with terpenoids (10 μM each) 55%±4%; CB2: Δ9-THC 16%±5%, with terpenoids (10 μM each) 17%±4%). To investigate possible effect on desensitization of CB1 responses, all six terpenoids were added together with Δ9-THC and signaling measured continuously over 30 min. Terpenoids did not affect desensitization, after 30 min the control hyperpolarization recovered by 63%±6% in the presence of the terpenoids recovery was 61%±5%. Discussion: None of the six of the most common terpenoids in Cannabis directly activated CB1 or CB2, or modulated the signaling of the phytocannabinoid agonist Δ9-THC. These results suggest that if a phytocannabinoid-terpenoid entourage effect exists, it is not at the CB1 or CB2 receptor level. It remains possible that terpenoids activate CB1 and CB2 signaling pathways that do not involve potassium channels; however, it seems more likely that they may act at different molecular target(s) in the neuronal circuits important for the behavioral effect of Cannabis.

Behavioral Hearing Thresholds and Distortion Product Otoacoustic Emissions in Cannabis Smokers

Purpose Cannabis is a widely used drug both medically and recreationally. The aim of this study was to determine if cannabis smoking is associated with changes in auditory function, as measured by behavioral hearing thresholds and/or distortion product otoacoustic emissions (DPOAEs). Method We investigated hearing thresholds and 2f₁-f₂ DPOAEs in 20 cannabis smokers and 20 nonsmokers between 18 and 28 years old. Behavioral thresholds were obtained from 0.25 to 16 kHz. DPOAEs were measured using discrete tones between f₂ of 0.5 and 19.03 kHz using an f₂/f₁ ratio of 1.22 and L₁/L₂ = 65/55 dB SPL. Thresholds and DPOAE amplitudes were compared between groups using linear mixed-effects models with sex and frequency as predictors. Results Behavioral thresholds in smokers did not differ significantly between smokers and nonsmokers (all ps > .05). Although not significant, long-term smokers exhibited poorer thresholds than short-term smokers and nonsmokers. Smokers generally exhibited lower DPOAE amplitudes than nonsmokers, although the differences were not significant. Male smokers had significantly poorer DPOAE amplitudes than male nonsmokers in the low frequencies (f₂ ≤ 2 kHz; p = .0245). Conclusion Results indicate that smoking cannabis may negatively alter the function of outer hair cells in young men. This subtle cochleopathology is evident in the absence of measurable differences in behavioral hearing thresholds between cannabis smokers and nonsmokers.

Denying renal transplantation to an adolescent medical cannabis user: An ethical case study

Medical cannabis is now legal in over half of the United States. As more patients adopt this unconventional therapy, it is inevitable that potential transplant recipients will disclose their cannabis use during transplant evaluation. Transplant teams are tasked with the decision to utilize a pressure resource, often with little guidance from international and national professional organizations. Many healthcare providers remain uniformed or misinformed about the risks of cannabis use and organ transplantation. In order to illustrate the multifaceted and complex evaluation of transplant patients using medical cannabis, this article presents the case of a 20-year-old woman recommended for renal transplant who was originally denied active listing due to her medical cannabis use. A review of the literature explores the perceived and actual risks of cannabis use in the immunocompromised patient. Furthermore, a discussion of the ethics of medical cannabis use and organ transplantation is included with recommendations for multidisciplinary transplant teams.

Cannabidiol (CBD) content in vaporized cannabis does not prevent tetrahydrocannabinol (THC)-induced impairment of driving and cognition

BACKGROUND

The main psychoactive component of cannabis, delta-9-tetrahydrocannabinol (THC), can impair driving performance. Cannabidiol (CBD), a non-intoxicating cannabis component, is thought to mitigate certain adverse effects of THC. It is possible then that cannabis containing equivalent CBD and THC will differentially affect driving and cognition relative to THC-dominant cannabis.

AIMS

The present study investigated and compared the effects of THC-dominant and THC/CBD equivalent cannabis on simulated driving and cognitive performance.

METHODS

In a randomized, double-blind, within-subjects crossover design, healthy volunteers (n = 14) with a history of light cannabis use attended three outpatient experimental test sessions in which simulated driving and cognitive performance were assessed at two timepoints (20-60 min and 200-240 min) following vaporization of 125 mg THC-dominant (11% THC; < 1% CBD), THC/CBD equivalent (11% THC, 11% CBD), or placebo (< 1% THC/CBD) cannabis.

RESULTS/OUTCOMES

Both active cannabis types increased lane weaving during a car-following task but had little effect on other driving performance measures. Active cannabis types impaired performance on the Digit Symbol Substitution Task (DSST), Divided Attention Task (DAT) and Paced Auditory Serial Addition Task (PASAT) with impairment on the latter two tasks worse with THC/CBD equivalent cannabis. Subjective drug effects (e.g., "stoned") and confidence in driving ability did not vary with CBD content. Peak plasma THC concentrations were higher following THC/CBD equivalent cannabis relative to THC-dominant cannabis, suggesting a possible pharmacokinetic interaction.

CONCLUSIONS/INTERPRETATION

Cannabis containing equivalent concentrations of CBD and THC appears no less impairing than THC-dominant cannabis, and in some circumstances, CBD may actually exacerbate THC-induced impairment.

Interactions between recreational cannabis use and cognitive function: lessons from functional magnetic resonance imaging

Cannabis use is becoming increasingly popular as a growing number of states pass legislation to legalize cannabis and cannabis-derived products for recreational and/or medical purposes. Given the widespread use of cannabis, it is critical to understand the neural consequences related to cannabis use. In this review, we focus on evidence from functional magnetic resonance imaging studies that document acute and residual alterations in brain function during tasks spanning a variety of cognitive domains: executive function, attention and working memory, memory, motor skills, error monitoring, and reward and affective processing. Although it is clear that cannabis affects brain function, the findings are somewhat inconsistent; variables that potentially affect study outcomes are outlined, including a discussion of the impact of chronological age and age of cannabis onset as well as length of abstinence at the time of assessment, which are important considerations when measuring cannabis use patterns. Inherent differences between recreational/adult cannabis use versus use for medical purposes are also discussed, given their importance to public policy decisions.

Cannabidiol modulation of antinociceptive tolerance to Δ9-tetrahydrocannabinol

RATIONALE

Humans typically self-administer cannabidiol (CBD) and delta-9-tetrahydrocannabinol (THC) together repeatedly (as in cannabis, cannabis extract, or Sativex®) to relieve pain. It has been suggested that one benefit of the drug combination may be decreased tolerance development.

OBJECTIVE

The present study compared the development of tolerance to the antinociceptive effects of THC given alone versus combined with CBD, in rats.

METHODS

THC dose-effect curves on tail withdrawal and paw pressure tests were obtained before and after twice-daily treatment with vehicle or CBD (10 mg/kg), plus vehicle or THC (3.6 mg/kg females; 9.3 mg/kg males) for 4 days.

RESULTS

On the first day, THC was more potent in females than males on both nociceptive tests. From pre- to post-chronic (day 1 to day 6), THC potency on the tail withdrawal test decreased more in females than males, and rats that had been treated with CBD + THC repeatedly showed greater rightward/downward shifts of the THC dose-effect curve than rats that had been treated with THC alone. Analysis of blood samples taken after day 6 testing showed that serum THC levels were higher in CBD + THC-treated females than in vehicle + THC-treated females, and THC's active metabolite 11-OH-THC and its inactive metabolite THC-COOH were lower in CBD + THC-treated rats than in vehicle + THC-treated rats of both sexes. CBD also increased serum levels of the active metabolite cannabinol in both sexes.

CONCLUSION

The decrease in THC's antinociceptive effects after repeated CBD exposure may be due to CBD-induced inhibition of THC metabolism, and/or antagonism of THC effects that emerges with repeated CBD treatment.

The neuropsychopharmacology of cannabis: A review of human imaging studies

The laws governing cannabis are evolving worldwide and associated with changing patterns of use. The main psychoactive drug in cannabis is Δ⁹-tetrahydrocannabinol (THC), a partial agonist at the endocannabinoid CB₁ receptor. Acutely, cannabis and THC produce a range of effects on several neurocognitive and pharmacological systems. These include effects on executive, emotional, reward and memory processing via direct interactions with the endocannabinoid system and indirect effects on the glutamatergic, GABAergic and dopaminergic systems. Cannabidiol, a non-intoxicating cannabinoid found in some forms of cannabis, may offset some of these acute effects. Heavy repeated cannabis use, particularly during adolescence, has been associated with adverse effects on these systems, which increase the risk of mental illnesses including addiction and psychosis. Here, we provide a comprehensive state of the art review on the acute and chronic neuropsychopharmacology of cannabis by synthesizing the available neuroimaging research in humans. We describe the effects of drug exposure during development, implications for understanding psychosis and cannabis use disorder, and methodological considerations. Greater understanding of the precise mechanisms underlying the effects of cannabis may also give rise to new treatment targets.

Mental Health-related Emergency Department Visits Associated With Cannabis in Colorado

BACKGROUND

Cannabis legalization in Colorado resulted in increased cannabis-associated health care utilization. Our objective was to examine cooccurrence of cannabis and mental health diagnostic coding in Colorado emergency department (ED) discharges and replicate the study in a subpopulation of ED visits where cannabis involvement and psychiatric diagnosis were confirmed through medical review.

METHODS

We collected statewide ED International Classification of Diseases, 9th Revision, Clinical Modification diagnoses from the Colorado Hospital Association and a subpopulation of ED visits from a large, academic hospital from 2012 to 2014. Diagnosis codes identified visits associated with mental health and cannabis. Codes for mental health conditions and cannabis were confirmed by manual records review in the academic hospital subpopulation. Prevalence ratios (PRs) of mental health ED discharges were calculated to compare cannabis-associated visits to those without cannabis. Rates of mental health and cannabis-associated ED discharges were examined over time.

RESULTS

Statewide data demonstrated a fivefold higher prevalence of mental health diagnoses in cannabis-associated ED visits (PR = 5.35, 95% confidence interval [CI], 5.27-5.43) compared to visits without cannabis. The hospital subpopulation supported this finding with a fourfold higher prevalence of psychiatric complaints in cannabis attributable ED visits (PR = 4.87, 95% CI = 4.36-5.44) compared to visits not attributable to cannabis. Statewide rates of ED visits associated with both cannabis and mental health significantly increased from 2012 to 2014 from 224.5 to 268.4 per 100,000 (p < 0.0001).

CONCLUSIONS

In Colorado, the prevalence of mental health conditions in ED visits with cannabis-associated diagnostic codes is higher than in those without cannabis. There is a need for further research determining if these findings are truly attributed to cannabis or merely coincident with concurrent increased use and availability.

Interactions between cannabis and schizophrenia in humans and rodents

In this review, we provide an overview of the relationship between cannabis use and the development of schizophrenia, using both animal and human studies. We further discuss the potential neural mechanism that may mediate the relationship between cannabis use and schizophrenia symptoms. We finally provide clinical implications and future studies that can further elucidate the relationship between cannabis and schizophrenia.

Tetrahydrocannabinol (THC) impairs encoding but not retrieval of verbal information

INTRODUCTION

Cannabis and agonists of the brain cannabinoid receptor (CB₁R) produce acute memory impairments in humans. However, the extent to which cannabinoids impair the component processes of encoding and retrieval has not been established in humans. The objective of this analysis was to determine whether the administration of Δ⁹-Tetrahydrocannabinol (THC), the principal psychoactive constituent of cannabis, impairs encoding and/or retrieval of verbal information.

MATERIALS AND METHODS

Healthy subjects were recruited from the community. Subjects were administered the Rey-Auditory Verbal Learning Test (RAVLT) either before administration of THC (experiment #1) (n=38) or while under the influence of THC (experiment #2) (n=57). Immediate and delayed recall on the RAVLT was compared. Subjects received intravenous THC, in a placebo-controlled, double-blind, randomized manner at doses known to produce behavioral and subjective effects consistent with cannabis intoxication.

RESULTS

Total immediate recall, short delayed recall, and long delayed recall were reduced in a statistically significant manner only when the RAVLT was administered to subjects while they were under the influence of THC (experiment #2) and not when the RAVLT was administered prior.

CONCLUSIONS

THC acutely interferes with encoding of verbal memory without interfering with retrieval. These data suggest that learning information prior to the use of cannabis or cannabinoids is not likely to disrupt recall of that information. Future studies will be necessary to determine whether THC impairs encoding of non-verbal information, to what extent THC impairs memory consolidation, and the role of other cannabinoids in the memory-impairing effects of cannabis.

CLINICAL TRIAL INFORMATION

Cannabinoids, Neural Synchrony, and Information Processing (THC-Gamma) http://clinicaltrials.gov/ct2/show/study/NCT00708994 NCT00708994 Pharmacogenetics of Cannabinoid Response http://clinicaltrials.gov/ct2/show/NCT00678730 NCT00678730.

Cannabis-associated psychosis: Neural substrate and clinical impact

Prospective epidemiological studies have consistently demonstrated that cannabis use is associated with an increased subsequent risk of both psychotic symptoms and schizophrenia-like psychoses. Early onset of use, daily use of high-potency cannabis, and synthetic cannabinoids carry the greatest risk. The risk-increasing effects are not explained by shared genetic predisposition between schizophrenia and cannabis use. Experimental studies in healthy humans show that cannabis and its active ingredient, delta-9-tetrahydrocannabinol (THC), can produce transient, dose-dependent, psychotic symptoms, as well as an array of psychosis-relevant behavioral, cognitive and psychophysiological effects; the psychotogenic effects can be ameliorated by cannabidiol (CBD). Findings from structural imaging studies in cannabis users have been inconsistent but functional MRI studies have linked the psychotomimetic and cognitive effects of THC to activation in brain regions implicated in psychosis. Human PET studies have shown that acute administration of THC weakly releases dopamine in the striatum but that chronic users are characterised by low striatal dopamine. We are beginning to understand how cannabis use impacts on the endocannabinoid system but there is much still to learn about the biological mechanisms underlying how cannabis increases risk of psychosis. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Neuroimaging studies towards understanding the central effects of pharmacological cannabis products on patients with epilepsy

Recent interest for the use of cannabis-derived products as therapeutic agents in the treatment of epilepsies has necessitated a reevaluation of their effects on brain and behavior. Overall, prolonged cannabis use is thought to result in functional and structural brain alterations. These effects may be dependent on a number of factors: e.g., which phytocannabinoid is used (e.g., cannabidiol (CBD) vs. tetrahyrocannabinol (THC)), the frequency of use (occasional vs. heavy), and at what age (prenatal, childhood, adulthood) the use began. However, due to the fact that there are over seven hundred constituents that make up the Cannabis sativa plant, it is difficult to determine which compound or combination of compounds is responsible for specific effects when studying recreational users. Therefore, this review focuses only on the functional MRI studies investigating the effects of specific pharmacological preparations of cannabis compounds, specifically THC, tetrahydrocannabivarin (THCV), and CBD, on brain function in healthy individuals and persons with epilepsy with references to non-epilepsy studies only to underline the gaps in research that need to be filled before cannabis-derived products are considered for a wide use in the treatment of epilepsy. This article is part of a Special Issue entitled "Cannabinoids and Epilepsy".

Building smart cannabis policy from the science up

Social attitudes and cultural norms around the issue of substance abuse are shifting rapidly around the world, leading to complex and unpredictable consequences. On the positive side, efforts to more intensely disseminate the scientific evidence for the many connections between chronic substance use and the emergence of measurable and discrete brain dysfunctions, has ushered in an evolving climate of acceptance and a new era of improved access to more effective interventions, at least in the United States. On the negative side, there has been a steady erosion in the public perception of the harms associated with the use of popular drugs, especially cannabis. This worrisome trend has sprouted at the convergence of several forces that have combined, more or less fortuitously, to effectively change long-standing policies away from prohibition and toward decriminalization or legalization. These forces include the outsized popularity of the cannabis plant among recreational users, the unflagging campaign by corporate lobbyists and patient advocates to mainstream its medicinal use, and the honest realization in some quarters of the deleterious impact of the drug war and its draconian cannabis laws, in particular, on society's most vulnerable populations. Updating drug policies is a desirable goal, and significant changes may indeed be warranted. However, there is a real concern when policy changes are hurriedly implemented without the required input from the medical, scientific, or policy research communities. Regardless of how well intentioned, such initiatives are bound to magnify the potential for unintended adverse consequences in the form of far ranging health and social costs. To minimize this risk, science must be front and center in this important policy debate. Here, we review the state of the science on cannabis and cannabinoid health effects, both adverse and therapeutic. We focus on the prevalence of use in different populations, the mechanisms by which cannabis exerts its effects (i.e., via the endocannabinoid system), and the double-edged potential of this system to inspire new medications, on one hand, and to cause short and long term harmful effects on the other. By providing knowledge of cannabis' broad ranging effects, we hope to enable better decision making regarding cannabis legislation and policy implementation.

Targeting the Endocannabinoid System in Psychiatric Illness

Prevalence of psychiatric disorders continues to rise globally, yet remission rates and patient outcome remain less than ideal. As a result, novel treatment approaches for these disorders are necessary to decrease societal economic burden, as well as increase individual functioning. The recent discovery of the endocannabinoid system has provided an outlet for further research into its role in psychiatric disorders, because efficacy of targeted treatments have been demonstrated in medical illnesses, including cancers, neuropathic pain, and multiple sclerosis. The present review will investigate the role of the endocannabinoid system in psychiatric disorders, specifically schizophrenia, depressive, anxiety, and posttraumatic stress disorders, as well as attention-deficit hyperactivity disorder. Controversy remains in prescribing medicinal cannabinoid treatments due to the fear of adverse effects. However, one must consider all potential limitations when determining the safety and tolerability of cannabinoid products, specifically cannabinoid content (ie, Δ-tetrahydrocannabinol vs cannabidiol) as well as study design. The potential efficacy of cannabinoid treatments in the psychiatric population is an emerging topic of interest that provides potential value going forward in medicine.

Delta-9-tetrahydrocannabinol and cannabidiol: Separating the chemicals from the "weed," a pharmacodynamic discussion

Cannabis is being increasingly used as a medical treatment for a variety of illnesses. However, the cannabis plant has more than 70 different phytocannabinoids with potential pharmacologic activity. Two of the most researched phytocannabinoids are delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). Evidence suggests CBD can decrease some of the psychomimetic effects of THC. This has led to the development of a new drug, Nabiximols, for the treatment of moderate to severe spasticity due to multiple sclerosis. A discussion of evidence supporting proposed pharmacodynamic interplay between CBD and THC is presented.

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.

Traditional marijuana, high-potency cannabis and synthetic cannabinoids: increasing risk for psychosis

Epidemiological evidence demonstrates that cannabis use is associated with an increased risk of psychotic outcomes, and confirms a dose-response relationship between the level of use and the risk of later psychosis. High-potency cannabis and synthetic cannabinoids carry the greatest risk. Experimental administration of tetrahydrocannabinol, the active ingredient of cannabis, induces transient psychosis in normal subjects, but this effect can be ameliorated by co-administration of cannabidiol. This latter is a constituent of traditional hashish, but is largely absent from modern high-potency forms of cannabis. Argument continues over the extent to which genetic predisposition is correlated to, or interacts with, cannabis use, and what proportion of psychosis could be prevented by minimizing heavy use. As yet, there is not convincing evidence that cannabis use increases risk of other psychiatric disorders, but there are no such doubts concerning its detrimental effect on cognitive function. All of the negative aspects are magnified if use starts in early adolescence. Irrespective of whether use of cannabis is decriminalized or legalized, the evidence that it is a component cause of psychosis is now sufficient for public health messages outlining the risk, especially of regular use of high-potency cannabis and synthetic cannabinoids.

Current Therapeutic Cannabis Controversies and Clinical Trial Design Issues

This overview covers a wide range of cannabis topics, initially examining issues in dispensaries and self-administration, plus regulatory requirements for production of cannabis-based medicines, particularly the Food and Drug Administration "Botanical Guidance." The remainder pertains to various cannabis controversies that certainly require closer examination if the scientific, consumer, and governmental stakeholders are ever to reach consensus on safety issues, specifically: whether botanical cannabis displays herbal synergy of its components, pharmacokinetics of cannabis and dose titration, whether cannabis medicines produce cyclo-oxygenase inhibition, cannabis-drug interactions, and cytochrome P450 issues, whether cannabis randomized clinical trials are properly blinded, combatting the placebo effect in those trials via new approaches, the drug abuse liability (DAL) of cannabis-based medicines and their regulatory scheduling, their effects on cognitive function and psychiatric sequelae, immunological effects, cannabis and driving safety, youth usage, issues related to cannabis smoking and vaporization, cannabis concentrates and vape-pens, and laboratory analysis for contamination with bacteria and heavy metals. Finally, the issue of pesticide usage on cannabis crops is addressed. New and disturbing data on pesticide residues in legal cannabis products in Washington State are presented with the observation of an 84.6% contamination rate including potentially neurotoxic and carcinogenic agents. With ongoing developments in legalization of cannabis in medical and recreational settings, numerous scientific, safety, and public health issues remain.

An Exploratory Human Laboratory Experiment Evaluating Vaporized Cannabis in the Treatment of Neuropathic Pain From Spinal Cord Injury and Disease

Using 8-hour human laboratory experiments, we evaluated the analgesic efficacy of vaporized cannabis in patients with neuropathic pain related to injury or disease of the spinal cord, most of whom were experiencing pain despite traditional treatment. After obtaining baseline data, 42 participants underwent a standardized procedure for inhaling 4 puffs of vaporized cannabis containing either placebo, 2.9%, or 6.7% delta 9-THC on 3 separate occasions. A second dosing occurred 3 hours later; participants chose to inhale 4 to 8 puffs. This flexible dosing was used to attempt to reduce the placebo effect. Using an 11-point numerical pain intensity rating scale as the primary outcome, a mixed effects linear regression model showed a significant analgesic response for vaporized cannabis. When subjective and psychoactive side effects (eg, good drug effect, feeling high, etc) were added as covariates to the model, the reduction in pain intensity remained significant above and beyond any effect of these measures (all P < .0004). Psychoactive and subjective effects were dose-dependent. Measurement of neuropsychological performance proved challenging because of various disabilities in the population studied. Because the 2 active doses did not significantly differ from each other in terms of analgesic potency, the lower dose appears to offer the best risk-benefit ratio in patients with neuropathic pain associated with injury or disease of the spinal cord.

PERSPECTIVE

A crossover, randomized, placebo-controlled human laboratory experiment involving administration of vaporized cannabis was performed in patients with neuropathic pain related to spinal cord injury and disease. This study supports consideration of future research that would include longer duration studies over weeks to months to evaluate the efficacy of medicinal cannabis in patients with central neuropathic pain.

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.

Oral Cannabidiol does not Alter the Subjective, Reinforcing or Cardiovascular Effects of Smoked Cannabis

Cannabidiol (CBD), a constituent of cannabis with few psychoactive effects, has been reported in some studies to attenuate certain aspects of Δ(9)-tetrahydrocannabinol (THC) intoxication. However, most studies have tested only one dose of CBD in combination with one dose of oral THC, making it difficult to assess the nature of this interaction. Further, the effect of oral CBD on smoked cannabis administration is unknown. The objective of this multi-site, randomized, double-blind, within-subject laboratory study was to assess the influence of CBD (0, 200, 400, 800 mg, p.o.) pretreatment on the reinforcing, subjective, cognitive, and physiological effects of smoked cannabis (0.01 (inactive), 5.30-5.80% THC). Non-treatment-seeking, healthy cannabis smokers (n=31; 17M, 14 F) completed eight outpatient sessions. CBD was administered 90 min prior to cannabis administration. The behavioral and cardiovascular effects of cannabis were measured at baseline and repeatedly throughout the session. A subset of participants (n=8) completed an additional session to measure plasma CBD concentrations after administration of the highest CBD dose (800 mg). Under placebo CBD conditions, active cannabis (1) was self-administered by significantly more participants than placebo cannabis and (2) produced significant, time-dependent increases in ratings of 'High', 'Good Effect', ratings of the cannabis cigarette (eg, strength, liking), and heart rate relative to inactive cannabis. CBD, which alone produced no significant psychoactive or cardiovascular effects, did not significantly alter any of these outcomes. Cannabis self-administration, subjective effects, and cannabis ratings did not vary as a function of CBD dose relative to placebo capsules. These findings suggest that oral CBD does not reduce the reinforcing, physiological, or positive subjective effects of smoked cannabis.

Human Laboratory Studies on Cannabinoids and Psychosis

Some of the most compelling evidence supporting an association between cannabinoid agonists and psychosis comes from controlled laboratory studies in humans. Randomized, double-blind, placebo-controlled, crossover laboratory studies demonstrate that cannabinoid agonists, including phytocannabinoids and synthetic cannabinoids, produce a wide range of positive, negative, and cognitive symptoms and psychophysiologic deficits in healthy human subjects that resemble the phenomenology of schizophrenia. These effects are time locked to drug administration, are dose related, and are transient and rarely necessitate intervention. The magnitude of effects is similar to the effects of ketamine but qualitatively distinct from other psychotomimetic drugs, including ketamine, amphetamine, and salvinorin A. Cannabinoid agonists have also been shown to transiently exacerbate symptoms in individuals with schizophrenia in laboratory studies. Patients with schizophrenia are more vulnerable than healthy control subjects to the acute behavioral and cognitive effects of cannabinoid agonists and experience transient exacerbation of symptoms despite treatment with antipsychotic medications. Furthermore, laboratory studies have failed to demonstrate any "beneficial" effects of cannabinoid agonists in individuals with schizophrenia-challenging the cannabis self-medication hypothesis. Emerging evidence suggests that polymorphisms of several genes related to dopamine metabolism (e.g., COMT, DAT1, and AKT1) may moderate the effects of cannabinoid agonists in laboratory studies. Cannabinoid agonists induce dopamine release, although the magnitude of release does not appear to be commensurate to the magnitude and spectrum of their acute psychotomimetic effects. Interactions between the endocannabinoid, gamma-aminobutyric acid, and glutamate systems and their individual and interactive effects on neural oscillations provide a plausible mechanism underlying the psychotomimetic effects of cannabinoids.