Cannabis Dampens the Effects of Music in Brain Regions Sensitive to Reward and Emotion

Mapping structural covariance networks of emotional withdrawal symptoms in males with methamphetamine use disorder during abstinence

Individuals with methamphetamine use disorder (MUD) often experience anxiety and depressive symptoms during abstinence, which can worsen the likelihood of relapse. Thus, it is essential to understand the neuro-mechanism behind methamphetamine use and its associated emotional withdrawal symptoms in order to develop effective clinical strategies. This study aimed to evaluate associations between emotional withdrawal symptoms and structural covariance networks (SCNs) based on cortical thickness (CTh) across the brain. The CTh measures were obtained from Tl-weighted MRI data from a sample of 48 males with MUD during abstinence and 48 male healthy controls. The severity of anxiety and depressive symptoms was assessed by the Hamilton Anxiety Scale (HAMA) and depression (HAMD) scales. Two important nodes belonging to the brain reward system, the right rostral anterior cingulate cortex (rACC) and medial prefrontal cortex (medPFC), were selected as seeds to conduct SCNs and modulation analysis by emotional symptoms. MUDs showed higher structural covariance between the right rACC and regions in the dorsal attention, right frontoparietal, auditory, visual and limbic networks. They also displayed higher structural covariance between the right medPFC and regions in the limbic network. Moreover, the modulation analysis showed that higher scores on HAMA were associated with increased covariance between the right rACC and the left parahippocampal and isthmus cingulate cortex in the default mode network. These outcomes shed light on the complex neurobiological mechanisms underlying methamphetamine use and its associated emotional withdrawal symptoms and may provide new insights into the development of effective treatments for MUD.

The Effects of Acute Cannabis With and Without Cannabidiol on Neural Reward Anticipation in Adults and Adolescents

BACKGROUND

Adolescents may respond differently to cannabis than adults, yet no previous functional magnetic resonance imaging study has examined acute cannabis effects in this age group. In this study, we investigated the neural correlates of reward anticipation after acute exposure to cannabis in adolescents and adults.

METHODS

This was a double-blind, placebo-controlled, randomized, crossover experiment. Forty-seven adolescents (n = 24, 12 females, ages 16-17 years) and adults (n = 23, 11 females, ages 26-29 years) matched on cannabis use frequency (0.5-3 days/week) completed the Monetary Incentive Delay task during functional magnetic resonance imaging after inhaling cannabis with 0.107 mg/kg Δ⁹-tetrahydrocannabinol ("THC") (8 mg THC for a 75-kg person) or with THC plus 0.320 mg/kg cannabidiol ("THC+CBD") (24 mg CBD for a 75-kg person), or placebo cannabis. We investigated reward anticipation activity with whole-brain analyses and region of interest analyses in the right and left ventral striatum, right and left anterior cingulate cortex, and right insula.

RESULTS

THC reduced anticipation activity compared with placebo in the right (p = .005, d= 0.49) and left (p = .003, d = 0.50) ventral striatum and the right insula (p = .01, d = 0.42). THC+CBD reduced activity compared with placebo in the right ventral striatum (p = .01, d = 0.41) and right insula (p = .002, d = 0.49). There were no differences between "THC" and "THC+CBD" conditions and no significant drug by age group interaction effect, supported by Bayesian analyses. There were no significant effects in the whole-brain analyses.

CONCLUSIONS

In weekly cannabis users, cannabis suppresses the brain's anticipatory reward response to money, and CBD does not modulate this effect. Furthermore, the adolescent reward circuitry is not differentially sensitive to acute effects of cannabis on reward anticipation.

Anhedonia, Apathy, Pleasure, and Effort-Based Decision-Making in Adult and Adolescent Cannabis Users and Controls

BACKGROUND

Cannabis use may be linked with anhedonia and apathy. However, previous studies have shown mixed results, and few have examined the association between cannabis use and specific reward sub-processes. Adolescents may be more vulnerable than adults to harmful effects of cannabis. This study investigated (1) the association between non-acute cannabis use and apathy, anhedonia, pleasure, and effort-based decision-making for reward; and (2) whether these relationships were moderated by age group.

METHODS

We used data from the "CannTeen" study. Participants were 274 adult (26-29 years) and adolescent (16-17 years) cannabis users (1-7 d/wk use in the past 3 months) and gender- and age-matched controls. Anhedonia was measured with the Snaith-Hamilton Pleasure Scale (n = 274), and apathy was measured with the Apathy Evaluation Scale (n = 215). Effort-based decision-making for reward was measured with the Physical Effort task (n = 139), and subjective wanting and liking of rewards was measured with the novel Real Reward Pleasure task (n = 137).

RESULTS

Controls had higher levels of anhedonia than cannabis users (F1,258 = 5.35, P = .02, η p2 = .02). There were no other significant effects of user-group and no significant user-group*age-group interactions. Null findings were supported by post hoc Bayesian analyses.

CONCLUSION

Our results suggest that cannabis use at a frequency of 3 to 4 d/wk is not associated with apathy, effort-based decision-making for reward, reward wanting, or reward liking in adults or adolescents. Cannabis users had lower anhedonia than controls, albeit at a small effect size. These findings are not consistent with the hypothesis that non-acute cannabis use is associated with amotivation.

Neutral CB1 Receptor Antagonists as Pharmacotherapies for Substance Use Disorders: Rationale, Evidence, and Challenge

Cannabinoid receptor 1 (CB1R) has been one of the major targets in medication development for treating substance use disorders (SUDs). Early studies indicated that rimonabant, a selective CB1R antagonist with an inverse agonist profile, was highly promising as a therapeutic for SUDs. However, its adverse side effects, such as depression and suicidality, led to its withdrawal from clinical trials worldwide in 2008. Consequently, much research interest shifted to developing neutral CB1R antagonists based on the recognition that rimonabant’s side effects may be related to its inverse agonist profile. In this article, we first review rimonabant’s research background as a potential pharmacotherapy for SUDs. Then, we discuss the possible mechanisms underlying its therapeutic anti-addictive effects versus its adverse effects. Lastly, we discuss the rationale for developing neutral CB1R antagonists as potential treatments for SUDs, the supporting evidence in recent research, and the challenges of this strategy. We conclude that developing neutral CB1R antagonists without inverse agonist profile may represent attractive strategies for the treatment of SUDs.

Task-independent acute effects of delta-9-tetrahydrocannabinol on human brain function and its relationship with cannabinoid receptor gene expression: A neuroimaging meta-regression analysis

The neurobiological mechanisms underlying the effects of delta-9-tetrahydrocannabinol (THC) remain unclear. Here, we examined the spatial acute effect of THC on human regional brain activation or blood flow (hereafter called 'activation signal') in a 'core' network of brain regions from 372 participants, tested using a within-subject repeated measures design under experimental conditions. We also investigated whether the neuromodulatory effects of THC are related to the local expression of the cannabinoid-type-1 (CB1R) and type-2 (CB2R) receptors. Finally, we investigated the dose-response relationship between THC and key brain substrates. These meta-analytic findings shed new light on the localisation of the effects of THC in the human brain, suggesting that THC has neuromodulatory effects in regions central to many cognitive tasks and processes, related to dose, with greater effects in regions with higher levels of CB1R expression.

Δ9-THC reduces reward-related brain activity in healthy adults

RATIONALE

Greater availability of cannabis in the USA has raised concerns about adverse effects of the drug, including possible amotivational states. Lack of motivation may be assessed by examining acute effects of cannabinoids on reward processing.

OBJECTIVES

This study examined single doses of delta-9-tetrahydrocannabinol (∆9-THC; 7.5, 15 mg oral) in healthy adults using a version of the monetary incentive delay (MID) task adapted for electroencephalography (EEG; e-MID) in a within-subjects, double blind design.

METHODS

Two phases of reward processing were examined: anticipation, which occurs with presentation of cues that indicate upcoming reward, punishment, or neutral conditions, and outcome, which occurs with feedback indicating hits or misses. During anticipation, we measured two event-related potential (ERP) components: the P300, which measures attention and motivation, and the LPP, which measures affective processing. During outcome processing, we measured P300 and LPP, as well as the RewP, which measures outcome evaluation.

RESULTS

We found that ∆9-THC modulated outcome processing, but not reward anticipation. Specifically, both doses of ∆9-THC (7.5 and 15 mg) reduced RewP amplitudes after outcome feedback (hits and misses) relative to placebo. ∆9-THC (15 mg) also reduced P300 and LPP amplitudes following hits compared to misses, relative to both placebo and 7.5 mg ∆9-THC.

CONCLUSIONS

These findings suggest that ∆9-THC dampens responses to both reward and loss feedback, which may reflect an "amotivational" state. Future studies are needed to determine generalizability of this effect, such as its pharmacological specificity and its specificity to monetary vs other types of reward.

Medical Students’ Attitudes, Knowledge, and Beliefs about Medical Cannabis: A Qualitative Descriptive Study

Background

There has been increased attention given to understanding the uses of medical cannabis (MC) for symptom management of various medical conditions. Physicians receive minimal training in medical school and rely mostly on anecdotal evidence; by proxy, medical students generally do receive formal training in MC. It is unknown how medical students perceive MC, including its efficacy, appropriateness in medicine, its possible adverse effects, and its value for patients. This study investigated medical students’ perceived knowledge, beliefs, and attitudes toward MC to better understand their knowledge about and attitudes toward MC. 

Method

Using a semi-structured interview guide, eight focus groups were conducted with 83 medical students via Zoom virtual meeting platform (Zoom Video Communications, Inc., San Jose, California, United States) in June 2022. The interviews were guided by the following content areas: (1) beliefs about cannabis' therapeutic utility, (2) perceived knowledge about MC, (3) the role of the physician regarding MC, (4) concern for cannabis’ adverse effects, and (5) MC education in the school curriculum. Data were analyzed using thematic analysis, an iterative, systematic process of coding patterns, and emerged themes in the interview data to explore medical students’ perceptions about MC. Themes were validated based on whether each theme captured distinct parts of the interview data and whether their content cohered meaningfully.

Results

Four themes emerged from the focus group interviews investigating medical students’ perceptions of MC: (1) erroneous beliefs about MC, (2) unreliable sources of information, (3) mixed attitudes toward legalization, and (4) desire for MC education while in medical school. Attitudes regarding MC in general, including legalization, varied by United States state of origin of the student and exposure to MC (e.g., use by family member). 

Conclusion

MC seems to be a significant issue for medical trainees who might be required to recommend it to patients and manage coexisting therapies. Cultivating new knowledge about students’ perceptions and perceived knowledge about medicinal options and dosing of MC is critical for medical educators as they design undergraduate curricular initiatives for future physicians.

Cell type specific cannabinoid CB1 receptor distribution across the human and non-human primate cortex

Alterations in cannabinoid CB1 receptor (CB1R) are implicated in various psychiatric disorders. CB1R participates in both depolarization induced suppression of inhibition (DSI) and depolarization induced suppression of excitation (DSE), suggesting its involvement in regulating excitatory and inhibitory (E/I) balance. Prior studies examining neuronal cell type specific CB1R distribution have been conducted near exclusively within rodents. Identification of these distribution patterns within the human and non-human primate cortex is essential to increase our insight into its function. Using co-labeling immunohistochemistry and fluorescent microscopy, we examined CB1R protein levels within excitatory and inhibitory boutons of male human and non-human primate prefrontal cortex and auditory cortices, regions involved in the behavioral effects of exogenous cannabinoid exposures. We found that CB1R was present in both bouton populations within all brain regions examined in both species. Significantly higher CB1R levels were found within inhibitory than within excitatory boutons across all regions in both species, although the cell type by brain region interactions differed between the two species. Our results support the importance of conducting more in-depth CB1R examinations to understand how cell type and brain region dependent differences contribute to regional E/I balance regulation, and how aberrations in CB1R distribution may contribute to pathology.

Individual and combined effects of cannabidiol and Δ9-tetrahydrocannabinol on striato-cortical connectivity in the human brain

BACKGROUND

Cannabidiol (CBD) and Δ⁹-tetrahydrocannabinol (THC) are the two major constituents of cannabis with contrasting mechanisms of action. THC is the major psychoactive, addiction-promoting, and psychotomimetic compound, while CBD may have opposite effects. The brain effects of these drugs alone and in combination are poorly understood. In particular, the striatum is implicated in the pathophysiology of several psychiatric disorders, but it is unclear how THC and CBD influence striato-cortical connectivity.

AIMS

To examine effects of THC, CBD, and THC + CBD on functional connectivity of striatal sub-divisions (associative, limbic and sensorimotor).

METHOD

Resting-state functional Magnetic Resonance Imaging (fMRI) was used across two within-subjects, placebo-controlled, double-blind studies, with a unified analysis approach.

RESULTS

Study 1 (N = 17; inhaled cannabis containing 8 mg THC, 8 mg THC + 10 mg CBD or placebo) showed strong disruptive effects of both THC and THC + CBD on connectivity in the associative and sensorimotor networks, but a specific effect of THC in the limbic striatum network which was not present in the THC + CBD condition. In Study 2 (N = 23, oral 600 mg CBD, placebo), CBD increased connectivity in the associative network, but produced only relatively minor disruptions in the limbic and sensorimotor networks.

OUTCOMES

THC strongly disrupts striato-cortical networks, but this effect is mitigated by co-administration of CBD in the limbic striatum network. Oral CBD administered has a more complex effect profile of relative increases and decreases in connectivity. The insula emerges as a key region affected by cannabinoid-induced changes in functional connectivity, with potential implications for understanding cannabis-related disorders, and the development of cannabinoid therapeutics.

Cannabis Use and Neuroadaptation: A Call for Δ 9 -Tetrahydrocannabinol Challenge Studies

Currently, the assessment of the neurobehavioral consequences of repeated cannabis use is restricted to studies in which brain function of chronic cannabis users is compared to that of non-cannabis using controls. The assumption of such studies is that changes in brain function of chronic users are caused by repeated and prolonged exposure to acute cannabis intoxication. However, differences in brain function between chronic cannabis users and non-users might also arise from confounding factors such as polydrug use, alcohol use, withdrawal, economic status, or lifestyle conditions. We propose a methodology that highlights the relevance of acute Δ⁹-tetrahydrocannabinol (THC) dosing studies for a direct assessment of neuroadaptations in chronic cannabis users. The approach includes quantification of neurochemical, receptor, and functional brain network changes in response to an acute cannabis challenge, as well as stratification of cannabis using groups ranging from occasional to cannabis-dependent individuals. The methodology allows for an evaluation of THC induced neuroadaptive and neurocognitive changes across cannabis use history, that can inform neurobiological models on reward driven, compulsive cannabis use.

Cannabinoids, reward processing, and psychosis

BACKGROUND

Evidence suggests that an overlap exists between the neurobiology of psychotic disorders and the effects of cannabinoids on neurocognitive and neurochemical substrates involved in reward processing.

AIMS

We investigate whether the psychotomimetic effects of delta-9-tetrahydrocannabinol (THC) and the antipsychotic potential of cannabidiol (CBD) are underpinned by their effects on the reward system and dopamine.

METHODS

This narrative review focuses on the overlap between altered dopamine signalling and reward processing induced by cannabinoids, pre-clinically and in humans. A systematic search was conducted of acute cannabinoid drug-challenge studies using neuroimaging in healthy subjects and those with psychosis RESULTS: There is evidence of increased striatal presynaptic dopamine synthesis and release in psychosis, as well as abnormal engagement of the striatum during reward processing. Although, acute THC challenges have elicited a modest effect on striatal dopamine, cannabis users generally indicate impaired presynaptic dopaminergic function. Functional MRI studies have identified that a single dose of THC may modulate regions involved in reward and salience processing such as the striatum, midbrain, insular, and anterior cingulate, with some effects correlating with the severity of THC-induced psychotic symptoms. CBD may modulate brain regions involved in reward/salience processing in an opposite direction to that of THC.

CONCLUSIONS

There is evidence to suggest modulation of reward processing and its neural substrates by THC and CBD. Whether such effects underlie the psychotomimetic/antipsychotic effects of these cannabinoids remains unclear. Future research should address these unanswered questions to understand the relationship between endocannabinoid dysfunction, reward processing abnormalities, and psychosis.

Value-based cognition and drug dependency

Value-based decision-making is thought to play an important role in drug dependency. Achieving elevated levels of euphoria or ameliorating dysphoria/pain may motivate goal-directed drug consumption in both drug-naïve and long-time users. In other words, drugs become viewed as the preferred means of attaining a desired internal state. The bias towards choosing drugs may affect one's cognition. Observed biases in learning, attention and memory systems within the brain gradually focus one's cognitive functions towards drugs and related cues to the exclusion of other stimuli. In this narrative review, the effects of drug use on learning, attention and memory are discussed with a particular focus on changes across brain-wide functional networks and the subsequent impact on behaviour. These cognitive changes are then incorporated into the cycle of addiction, an established model outlining the transition from casual drug use to chronic dependency. If drug use results in the elevated salience of drugs and their cues, the studies highlighted in this review strongly suggest that this salience biases cognitive systems towards the motivated pursuit of addictive drugs. This bias is observed throughout the cycle of addiction, possibly contributing to the persistent hold that addictive drugs have over the dependent. Taken together, the excessive valuation of drugs as the preferred means of achieving a desired internal state affects more than just decision-making, but also learning, attentional and mnemonic systems. This eventually narrows the focus of one's thoughts towards the pursuit and consumption of addictive drugs.

The acute and non-acute effects of cannabis on reward processing: A systematic review

Cannabis use has historically been thought to cause amotivation, but the relationship between cannabis and apathy, anhedonia, and reward processing remains poorly characterised. In this systematic review, we evaluated whether cannabis exposure acutely and/or non-acutely was associated with altered reward processing using questionnaire, behavioural, or functional neuroimaging measures. Questionnaire studies demonstrated greater anhedonia in adolescent cannabis users, and some indication of greater apathy in young adult cannabis users. Behavioural studies yielded some evidence of reduced reward learning in adolescent cannabis users, though there were too few studies in this category for reliable conclusions. Finally, longitudinal and acute functional neuroimaging studies showed an association between cannabis and blunted neural responses to reward, which did not emerge consistently in cross-sectional studies. The current results suggest that cannabis use is associated with specific impairments in reward and motivation. Future large-scale, longitudinal studies which use multiple behavioural and neuroimaging measures of reward processing may further clarify the impact of cannabis use on motivational and reward processes, and neural networks.

Acute effects of cannabis on speech illusions and psychotic-like symptoms: two studies testing the moderating effects of cannabidiol and adolescence

BACKGROUND

Acute cannabis administration can produce transient psychotic-like effects in healthy individuals. However, the mechanisms through which this occurs and which factors predict vulnerability remain unclear. We investigate whether cannabis inhalation leads to psychotic-like symptoms and speech illusion; and whether cannabidiol (CBD) blunts such effects (study 1) and adolescence heightens such effects (study 2).

METHODS

Two double-blind placebo-controlled studies, assessing speech illusion in a white noise task, and psychotic-like symptoms on the Psychotomimetic States Inventory (PSI). Study 1 compared effects of Cann-CBD (cannabis containing Δ-9-tetrahydrocannabinol (THC) and negligible levels of CBD) with Cann+CBD (cannabis containing THC and CBD) in 17 adults. Study 2 compared effects of Cann-CBD in 20 adolescents and 20 adults. All participants were healthy individuals who currently used cannabis.

RESULTS

In study 1, relative to placebo, both Cann-CBD and Cann+CBD increased PSI scores but not speech illusion. No differences between Cann-CBD and Cann+CBD emerged. In study 2, relative to placebo, Cann-CBD increased PSI scores and incidence of speech illusion, with the odds of experiencing speech illusion 3.1 (95% CIs 1.3-7.2) times higher after Cann-CBD. No age group differences were found for speech illusion, but adults showed heightened effects on the PSI.

CONCLUSIONS

Inhalation of cannabis reliably increases psychotic-like symptoms in healthy cannabis users and may increase the incidence of speech illusion. CBD did not influence psychotic-like effects of cannabis. Adolescents may be less vulnerable to acute psychotic-like effects of cannabis than adults.

The Effects of Acute Δ9-Tetrahydrocannabinol on Striatal Glutamatergic Function: A Proton Magnetic Resonance Spectroscopy Study

BACKGROUND

Cannabis and its main psychoactive component, Δ⁹-tetrahydrocannabinol (THC), can elicit transient psychotic symptoms. A key candidate biological mechanism of how THC induces psychotic symptoms is the modulation of glutamate in the brain. We sought to investigate the effects of acute THC administration on striatal glutamate levels and its relationship to the induction of psychotic symptoms.

METHODS

We used proton magnetic resonance spectroscopy to measure glutamate levels in the striatum in 20 healthy participants after THC (15 mg, oral) and matched placebo administration in a randomized, double-blind, placebo-controlled design. Psychotic symptoms were measured using the Psychotomimetic States Inventory.

RESULTS

We found that THC administration did not significantly change glutamate (glutamate plus glutamine relative to creatine) concentration in the striatum (p = .58; scaled Jeffreys-Zellner-Siow Bayes factor = 4.29). THC increased psychotic symptoms, but the severity of these symptoms was not correlated with striatal glutamate levels.

CONCLUSIONS

These findings suggest that oral administration of 15 mg of THC does not result in altered striatal glutamate levels. Further work is needed to clarify the effects of THC on striatal glutamate.

The Yin and Yang of Cannabis: A Systematic Review of Human Neuroimaging Evidence of the Differential Effects of Δ9-Tetrahydrocannabinol and Cannabidiol

Cannabidiol (CBD) and Δ9-tetrahydrocannabinol (THC) have been the most investigated cannabinoids at the human and preclinical levels, although the neurobiological mechanisms underlying their effects remain unclear. Human experimental evidence complemented by observational studies suggests that THC may have psychotogenic effects while CBD may have antipsychotic effects. However, whether their effects on brain function are consistent with their opposing behavioral effects remains unclear. To address this, here we synthesize neuroimaging evidence investigating the acute effects of THC and CBD on human brain function using a range of neuroimaging techniques, with an aim to identify the key brain substrates where THC and CBD have opposing effects. After a systematic search, a review of the available studies indicated marked heterogeneity. However, an overall pattern of opposite effect profiles of the two cannabinoids was evident with some degree of consistency, primarily attributed to the head-to-head challenge studies of THC and CBD. While head-to-head comparisons are relatively few, collectively the evidence suggests that opposite effects of THC and CBD may be present in the striatum, parahippocampus, anterior cingulate/medial prefrontal cortex, and amygdala, with opposite effects less consistently identified in other regions. Broadly, THC seems to increase brain activation and blood flow, whereas CBD seems to decrease brain activation and blood flow. Given the sparse evidence, there is a particular need to understand the mechanisms underlying their opposite behavioral effects because it may not only offer insights into the underlying pathophysiological mechanisms of psychotic disorders but also suggest potentially novel targets and biomarkers for drug discovery.

The why behind the high: determinants of neurocognition during acute cannabis exposure

Acute cannabis intoxication may induce neurocognitive impairment and is a possible cause of human error, injury and psychological distress. One of the major concerns raised about increasing cannabis legalization and the therapeutic use of cannabis is that it will increase cannabis-related harm. However, the impairing effect of cannabis during intoxication varies among individuals and may not occur in all users. There is evidence that the neurocognitive response to acute cannabis exposure is driven by changes in the activity of the mesocorticolimbic and salience networks, can be exacerbated or mitigated by biological and pharmacological factors, varies with product formulations and frequency of use and can differ between recreational and therapeutic use. It is argued that these determinants of the cannabis-induced neurocognitive state should be taken into account when defining and evaluating levels of cannabis impairment in the legal arena, when prescribing cannabis in therapeutic settings and when informing society about the safe and responsible use of cannabis.

Unraveling the Temporal Dynamics of Reward Signals in Music-Induced Pleasure with TMS

Music's ability to induce feelings of pleasure has been the subject of intense neuroscientific research lately. Prior neuroimaging studies have shown that music-induced pleasure engages cortico-striatal circuits related to the anticipation and receipt of biologically relevant rewards/incentives, but these reports are necessarily correlational. Here, we studied both the causal role of this circuitry and its temporal dynamics by applying transcranial magnetic stimulation (TMS) over the left dorsolateral PFC combined with fMRI in 17 male and female participants. Behaviorally, we found that, in accord with previous findings, excitation of fronto-striatal pathways enhanced subjective reports of music-induced pleasure and motivation, whereas inhibition of the same circuitry led to the reduction of both. fMRI activity patterns indicated that these behavioral changes were driven by bidirectional TMS-induced alteration of fronto-striatal function. Specifically, changes in activity in the NAcc predicted modulation of both hedonic and motivational responses, with a dissociation between pre-experiential versus experiential components of musical reward. In addition, TMS-induced changes in the fMRI functional connectivity between the NAcc and frontal and auditory cortices predicted the degree of modulation of hedonic responses. These results indicate that the engagement of cortico-striatal pathways and the NAcc, in particular, is indispensable to experience rewarding feelings from music.SIGNIFICANCE STATEMENT Neuroimaging studies have shown that music-induced pleasure engages cortico-striatal circuits involved in the processing of biologically relevant rewards. Yet, these reports are necessarily correlational. Here, we studied both the causal role of this circuitry and its temporal dynamics by combining brain stimulation over the frontal cortex with functional imaging. Behaviorally, we found that excitation and inhibition of fronto-striatal pathways enhanced and disrupted, respectively, subjective reports of music-induced pleasure and motivation. These changes were associated with changes in NAcc activity and NAcc coupling with frontal and auditory cortices, dissociating between pre-experimental versus experiential components of musical reward. These results indicate that the engagement of cortico-striatal pathways, and the NAcc in particular, is indispensable to experience rewarding feeling from music.

High genes: Genetic underpinnings of cannabis use phenotypes

Cannabis is one of the most widely used substances across the globe and its use has a substantial heritable component. However, the heritability of cannabis use varies according to substance use phenotype, suggesting that a unique profile of gene variants may contribute to the different stages of use, such as age of use onset, lifetime use, cannabis use disorder, and withdrawal and craving during abstinence. Herein, we review a subset of genes identified by candidate gene, family-based linkage, and genome-wide association studies related to these cannabis use phenotypes. We also describe their relationships with other substances, and their functions at the neurobiological, cognitive, and behavioral levels to hypothesize the role of these genes in cannabis use risk. Delineating genetic risk factors in the various stages of cannabis use will provide insight into the biological mechanisms related to cannabis use and highlight points of intervention prior to and following the development of dependence, as well as identify targets to aid drug development for treating problematic cannabis use.

The Impact of Cannabidiol on Human Brain Function: A Systematic Review

Background: Accumulating evidence suggests that the non-intoxicating cannabinoid compound cannabidiol (CBD) may have antipsychotic and anxiolytic properties, and thus may be a promising new agent in the treatment of psychotic and anxiety disorders. However, the neurobiological substrates underlying the potential therapeutic effects of CBD are still unclear. The aim of this systematic review is to provide a detailed and up-to-date systematic literature overview of neuroimaging studies that investigated the acute impact of CBD on human brain function.

Methods: Papers published until May 2020 were included from PubMed following a comprehensive search strategy and pre-determined set of criteria for article selection. We included studies that examined the effects of CBD on brain function of healthy volunteers and individuals diagnosed with a psychiatric disorder, comprising both the effects of CBD alone as well as in direct comparison to those induced by ∆9-tetrahydrocannabinol (THC), the main psychoactive component of Cannabis.

Results: One-ninety four studies were identified, of which 17 met inclusion criteria. All studies investigated the acute effects of CBD on brain function during resting state or in the context of cognitive tasks. In healthy volunteers, acute CBD enhanced fronto-striatal resting state connectivity, both compared to placebo and THC. Furthermore, CBD modulated brain activity and had opposite effects when compared to THC following task-specific patterns during various cognitive paradigms, such as emotional processing (fronto-temporal), verbal memory (fronto-striatal), response inhibition (fronto-limbic-striatal), and auditory/visual processing (temporo-occipital). In individuals at clinical high risk for psychosis and patients with established psychosis, acute CBD showed intermediate brain activity compared to placebo and healthy controls during cognitive task performance. CBD modulated resting limbic activity in subjects with anxiety and metabolite levels in patients with autism spectrum disorders.

Conclusion: Neuroimaging studies have shown that acute CBD induces significant alterations in brain activity and connectivity patterns during resting state and performance of cognitive tasks in both healthy volunteers and patients with a psychiatric disorder. This included modulation of functional networks relevant for psychiatric disorders, possibly reflecting CBD’s therapeutic effects. Future studies should consider replication of findings and enlarge the inclusion of psychiatric patients, combining longer-term CBD treatment with neuroimaging assessments.

Adverse Effects of Recreational and Medical Cannabis

PURPOSE OF REVIEW

This comprehensive review discusses the adverse effects known today about marijuana, for either medical or recreational use. It reviews the role of cannabis in the treatment of chronic pain, cognitive and neurological adverse effects, special cases and addiction.

RECENT FINDINGS

Cannabinoids work through the endocannabinoids system and inhibit the release of GABA and glutamate in the brain, impact neuromodulation, as well as dopamine, acetylcholine and norepinephrine release. They affect reward, learning and pain. The use of cannabis is increasing nationally and world-wide for both recreational and medicinal purposes, however, there is relatively only low quality evidence to the efficacy and adverse effects of this. Cannabis and its derivatives may be used for treatment of chronic pain. They are via CB1 receptors that are thought to modulate nociceptive signals in the brain. CB2 receptors in the DRG likely affect pain integration in the afferent pathways, and peripherally CB2 also affects noradrenergic pathways influencing pain. A large proportion of users may see more than 50% of chronic pain alleviation compared with placebo. Cannabis affects cognition, most notably executive function, memory and attention, and may deteriorate the boundary between emotional and executive processing. Cannabis impairs memory in the short run, which become more significant with chronic use, and may also be accompanied by poorer effort, slower processing and impacted attention. It is generally believed that long-term use and earlier age are risk factor for neurocognitive deficits; neuroimaging studies have shown reduced hippocampal volume and density. Executive functions and memory are worse in adolescent users versus adults. Cannabis addiction is different and likely less common than other addictive substances, but up to 10% of users meet criteria for lifetime cannabis dependence. Addiction patterns may be linked to genetic and epigenetic differences. It is still unclear whether abstinence reverses patterns of addiction, and more research is required into this topic.

SUMMARY

Cannabis use has become more abundant for both medical and recreational use. It carries likely benefits in the form of analgesia, anti-emesis and improved appetite in chronic patients. The evidence reviewing adverse effects of this use are still limited, however, exiting data points to a clear link with neurocognitive deterioration, backed by loss of brain volume and density. Addiction is likely complex and variable, and no good data exists to support treatment at this point. It is becoming clear that use in earlier ages carries a higher risk for long-term deficits. As with any other drug, these risks should be considered alongside benefits prior to a decision on cannabis use.

Efficacy and acceptability of cannabinoids for anxiety disorders in adults: A systematic review & meta-analysis

OBJECTIVE

The aim of this study was to assess the efficacy and acceptability of cannabinoids for the treatment of anxiety disorders.

METHODS

For this systematic review and meta-analysis, we searched for randomized trials utilizing cannabinoids for the treatment of adults with anxiety disorders. Primary outcomes were reduction in anxiety disorder symptoms, and study discontinuation due to adverse events. Evidence was synthesized as rate ratios (RRs) and as standardized mean differences (SMDs) using random-effects meta-analyses.

RESULTS

A total of 14 eligible trials representing 1548 individuals (median age: 33 years; range: 28-44; 66% male) were identified. Cannabinoids reduced anxiety symptoms (SMD = -1.85, 95% CI: -2.61 to -1.09) without causing significant adverse events. Greater efficacy was observed among younger patients (p < 0.01) and with longer treatment (p < 0.01). However, publication bias was substantial, and after correction, the overall anxiolytic effect was not statistically significant.

CONCLUSIONS

While cannabinoids may be of potential value in the treatment of anxiety disorders, the routine use of these treatments is not supported by the available evidence after correction for publication bias.

A coordinate-based meta-analysis of music-evoked emotions

Since the publication of the first neuroscience study investigating emotion with music about two decades ago, the number of functional neuroimaging studies published on this topic has increased each year. This research interest is in part due to the ubiquity of music across cultures, and to music's power to evoke a diverse range of intensely felt emotions. To support a better understanding of the brain correlates of music-evoked emotions this article reports a coordinate-based meta-analysis of neuroimaging studies (n = 47 studies with n = 944 subjects). The studies employed a range of diverse experimental approaches (e.g., using music to evoke joy, sadness, fear, tension, frissons, surprise, unpleasantness, or feelings of beauty). The results of an activation likelihood estimation (ALE) indicate large clusters in a range of structures, including amygdala, anterior hippocampus, auditory cortex, and numerous structures of the reward network (ventral and dorsal striatum, anterior cingulate cortex, orbitofrontal cortex, secondary somatosensory cortex). The results underline the rewarding nature of music, the role of the auditory cortex as an emotional hub, and the role of the hippocampus in attachment-related emotions and social bonding.

The acute effects of cannabidiol on the neural correlates of reward anticipation and feedback in healthy volunteers

BACKGROUND

Cannabidiol has potential therapeutic benefits for people with psychiatric disorders characterised by reward function impairment. There is existing evidence that cannabidiol may influence some aspects of reward processing. However, it is unknown whether cannabidiol acutely affects brain function underpinning reward anticipation and feedback.

HYPOTHESES

We predicted that cannabidiol would augment brain activity associated with reward anticipation and feedback.

METHODS

We administered a single 600 mg oral dose of cannabidiol and matched placebo to 23 healthy participants in a double-blind, placebo-controlled, repeated-measures design. We employed the monetary incentive delay task during functional magnetic resonance imaging to assay the neural correlates of reward anticipation and feedback. We conducted whole brain analyses and region-of-interest analyses in pre-specified reward-related brain regions.

RESULTS

The monetary incentive delay task elicited expected brain activity during reward anticipation and feedback, including in the insula, caudate, nucleus accumbens, anterior cingulate and orbitofrontal cortex. However, across the whole brain, we did not find any evidence that cannabidiol altered reward-related brain activity. Moreover, our Bayesian analyses showed that activity in our regions-of-interest was similar following cannabidiol and placebo. Additionally, our behavioural measures of motivation for reward did not show a significant difference between cannabidiol and placebo.

DISCUSSION

Cannabidiol did not acutely affect the neural correlates of reward anticipation and feedback in healthy participants. Future research should explore the effects of cannabidiol on different components of reward processing, employ different doses and administration regimens, and test its reward-related effects in people with psychiatric disorders.

'Standard THC units': a proposal to standardize dose across all cannabis products and methods of administration

BACKGROUND AND AIMS

Cannabis products are becoming increasingly diverse, and vary considerably in concentrations of ∆⁹ -tetrahydrocannabinol (THC) and cannabidiol (CBD). Higher doses of THC can increase the risk of harm from cannabis, while CBD may partially offset some of these effects. Lower Risk Cannabis Use Guidelines currently lack recommendations based on quantity of use, and could be improved by implementing standard units. However, there is currently no consensus on how units should be measured or standardized among different cannabis products or methods of administration.

ARGUMENT

Existing proposals for standard cannabis units have been based on specific methods of administration (e.g. joints) and these may not capture other methods, including pipes, bongs, blunts, dabbing, vaporizers, vape pens, edibles and liquids. Other proposals (e.g. grams of cannabis) cannot account for heterogeneity in THC concentrations among different cannabis products. Similar to alcohol units, we argue that standard cannabis units should reflect the quantity of primary active pharmacological constituents (dose of THC). On the basis of experimental and ecological data, public health considerations and existing policy, we propose that a 'standard THC unit' should be fixed at 5 mg THC for all cannabis products and methods of administration. If supported by sufficient evidence in future, consumption of standard CBD units might offer an additional strategy for harm reduction.

CONCLUSIONS

Standard ∆⁹ -tetrahydrocannabinol (THC) units can potentially be applied among all cannabis products and methods of administration to guide consumers and promote safer patterns of use.

Acute neuroradiological, behavioral, and physiological effects of nose-only exposure to vaporized cannabis in C57BL/6 mice

Objective: The rapid increase of cannabis consumption reinforces the need to elucidate the health hazards of this practice. The presence of fine particulate matter in cannabis smoke and vapor poses a major concern, as it may contribute to cardiopulmonary disease. To facilitate the assessment of risks associated with cannabis inhalation, we developed and characterized a method for exposing mice to cannabis in a way that mimics the delivery of the drug to the airways of smokers. Materials and Methods: Cannabis (10.3% THC, 0.05% CBD) was vaporized to generate aerosols with a reproducible particle profile. Aerosols were acutely delivered to male, adult C57BL/6 mice via a nose-only exposure system. Serum THC levels were measured for increasing cannabis doses. Blood pressure and heart rate were recorded at baseline and following exposure. Behavioral response to cannabis inhalation in the open field was documented. Awake neurological activity upon cannabis exposure was monitored using BOLD fMRI.Results and Discussion: Cannabis aerosols contained particles with count median diameter of 243 ± 39 nm and geometric standard deviation of 1.56 ± 0.06. Blood serum THC levels increased linearly with aerosolized mass and peaked at 136 ± 5 ng/mL. Cannabis inhalation decreased heart rate and blood pressure but promoted anxiety-like behavior. Observed differences in BOLD activation volumes linked cannabis to increased awareness to sensory stimuli and reduced behavioral arousal.Conclusions: Quantified physiological, behavioral, and neurological responses served as validation for our mouse model of cannabis inhalation. Animal models of aerosol exposure will be instrumental for uncovering the health outcomes of chronic cannabis use.

How does cannabidiol (CBD) influence the acute effects of delta-9-tetrahydrocannabinol (THC) in humans? A systematic review

The recent liberalisation of cannabis regulation has increased public and scientific debate about its potential benefits and risks. A key focus has been the extent to which cannabidiol (CBD) might influence the acute effects of delta-9-tetrahydrocannabinol (THC), but this has never been reviewed systematically. In this systematic review of how CBD influences the acute effects of THC we identified 16 studies involving 466 participants. Ten studies were judged at low risk of bias. The findings were mixed, although CBD was found to reduce the effects of THC in several studies. Some studies found that CBD reduced intense experiences of anxiety or psychosis-like effects of THC and blunted some of the impairments on emotion and reward processing. However, CBD did not consistently influence the effects of THC across all studies and outcomes. There was considerable heterogeneity in dose, route of administration and THC:CBD ratio across studies and no clear dose-response profile emerged. Although findings were mixed, this review suggests that CBD may interact with some acute effects of THC.

Dissociable effects of cannabis with and without cannabidiol on the human brain's resting-state functional connectivity

BACKGROUND

Two major constituents of cannabis are Δ⁹-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is the main psychoactive component; CBD may buffer the user against the harmful effects of THC.

AIMS

We examined the effects of two strains of cannabis and placebo on the human brain's resting-state networks using fMRI.

METHODS

Seventeen healthy volunteers (experienced with cannabis, but not regular users) underwent three drug treatments and scanning sessions. Treatments were cannabis containing THC (Cann-CBD; 8 mg THC), cannabis containing THC with CBD (Cann+CBD; 8 mg THC + 10 mg CBD), and matched placebo cannabis. Seed-based resting-state functional connectivity analyses were performed on three brain networks: the default mode (DMN; defined by positive connectivity with the posterior cingulate cortex: PCC+), executive control (ECN; defined by negative connectivity with the posterior cingulate cortex: PCC-) and salience (SAL; defined by positive connectivity with the anterior insula: AI+) network.

RESULTS

Reductions in functional connectivity (relative to placebo) were seen in the DMN (PCC+) and SAL (AI+) networks for both strains of cannabis, with spatially dissociable effects. Across the entire salience network (AI+), Cann-CBD reduced connectivity relative to Cann+CBD. The PCC in the DMN was specifically disrupted by Cann-CBD, and this effect correlated with subjective drug effects, including feeling 'stoned' and 'high'.

CONCLUSIONS

THC disrupts the DMN, and the PCC is a key brain region involved in the subjective experience of THC intoxication. CBD restores disruption of the salience network by THC, which may explain its potential to treat disorders of salience such as psychosis and addiction.

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.

Illicit and prescription drug misuse as reported to the Maine Diversion Alert Program

BACKGROUND

The opioid epidemic is rapidly evolving and new tools are needed to combat drug abuse. The Maine Diversion Alert Program (DAP) is an informational resource that facilitates communication about drug arrests between the criminal justice and healthcare fields. The objectives of this report were to: (1) describe the illegal and prescription pharmaceuticals reported to the DAP; (2) determine if the drugs implicated in arrests changed from the first to latter half of 2016; (3) identify the demographic and other characteristics of arrestees; and (4) outline the strengths and limitations of the DAP for other areas considering implementing similar programs.

METHODS

The arrests (N=2,368, 31.4% female, mean age=33.7, SD=9.9, Min=18, Max=71.5) reported to the DAP were examined. Drugs were classified by Drug Enforcement Administration Schedule (I-V, non-controlled prescription) and into families (opioids, stimulants, sedatives, hallucinogens, and other). A comparison between the first and second half of 2016 and arrest by county was completed.

RESULTS

Arrests involved 2,957 substances (drugs and paraphernalia). Most arrests (80.6%) involved a single drug. One-third (33.2%) of arrests involved illicit drugs (i.e. Schedule I) and three-fifths (59.8%) were for controlled prescription medical drugs (i.e. Schedule II-V), and a minority (6.8%) involved non-controlled prescription drugs (e.g. gabapentin, bupropion). Opioids (e.g. heroin, buprenorphine, and oxycodone) accounted for over-half (51.3%) of arrests followed by stimulants (29.0%, e.g. cocaine), and sedatives (7.6%). Arrests for oxycodone significantly decreased (51.9%) and alprazolam increased (89.3%) during 2016. Arrestees for non-controlled prescription drugs were older than arrestees for illegal drugs. Arrests, correcting for population, were most common in more urban (e.g. Androscoggin and Cumberland) counties.

CONCLUSIONS

Opioids (illicit and prescription) account for over half of all arrests. However, arrests for oxycodone decreased while arrests for benzodiazepines, and especially alprazolam, increased in 2016. The DAP is a novel source of information for healthcare decisions and can empirically inform law enforcement about drug misuse and addiction.