Cannabinoids and Psychosis

Cannabidiol versus placebo as adjunctive treatment in early psychosis: study protocol for randomized controlled trial

BACKGROUND

Psychotic disorders are a leading cause of disability in young adults. Antipsychotics have been the primary intervention for psychosis for over 60 years, and yet, we have made little progress in treating negative symptoms, neurocognition, and functional disability. There is growing evidence that cannabidiol (CBD) is effective in treating positive psychotic symptoms, possibly also negative and neurocognitive symptoms, and moreover is well tolerated compared to other psychotropic medications. Anecdotally, patients participating in the Cognitive Assessment and Risk Evaluation (CARE) Early Psychosis Treatment Program at the University of California, San Diego, are self-administering CBD and report subjective improvement in stress, anxiety, and ability to cope with symptoms. The overarching aim of the trial is to explore the effectiveness of CBD augmentation on symptoms and neurocognition in early psychosis while also exploring the mechanism of action of CBD and predictors of response to treatment. The mechanism by which cannabidiol has a therapeutic effect on psychosis is poorly understood. Recent evidence has suggested that CBD may reduce stress and pro-inflammatory biomarker levels. Endocannabinoids also have powerful roles in eating behavior, reward, and mood, indicating these neurotransmitters may play a role in reducing hyperphagia and metabolic abnormalities that are present early in the course of psychotic illness and exacerbated by antipsychotic medication. The neurophysiological effects of CBD have been studied in animal models of psychosis that show improvements in information processing in response to CBD, but there are no studies in individuals with early psychosis.

METHOD

A total of 120 individuals in the early stages of psychosis will be randomized to 1000 mg of CBD versus placebo as an adjunct to existing treatment in a 8-week, double-blind superiority randomized control trial. The primary outcome measures are symptoms and neurocognition.

DISCUSSION

We hypothesized that CBD will improve symptoms and neurocognition as well as secondary outcome measures of neurohormones, inflammation, eating behaviors, and information processing. Importantly, predictors, moderators, and mediators of the CBD effects will be examined. A better understanding of which individuals are likely to respond to CBD can inform treatment planning and personalize treatment.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04411225. Registered on June 2, 2020.

Cognitive behavioral therapy for insomnia to reduce cannabis use: Results from a pilot randomized controlled trial

BACKGROUND

Individuals with regular cannabis use demonstrate adverse health outcomes, yet infrequently seek treatment. Insomnia, a common co-occurring complaint, could be targeted to reduce cannabis use and improve functioning in these individuals. In an intervention development study, we refined and tested the preliminary efficacy of a telemedicine-delivered CBT for insomnia tailored to individuals with regular cannabis use for sleep (CBTi-CB-TM).

METHODS

In this single-blind randomized trial, fifty-seven adults (43 women, mean age 37.6 ± 12.8 years) with chronic insomnia and cannabis use for sleep ≥3 times/week received CBTi-CB-TM (n = 30) or sleep hygiene education (SHE-TM, n = 27). Participants completed self-reported assessments of insomnia (Insomnia Severity Index [ISI]) and cannabis use (Timeline Followback [TLFB] and daily diary data) at pre-treatment, post-treatment, and 8-week follow-up.

RESULTS

ISI scores improved significantly more in the CBTi-CB-TM compared to SHE-TM condition (β = -2.83, se=0.84, P = 0.004, d=0.81). At 8-week follow-up, 18/30 (60.0 %) CBTi-CB-TM compared to 4/27 (14.8 %) SHE-TM participants were in remission from insomnia (X2 =12.8, P = 0.0003). The TLFB showed a small reduction in past 30-day cannabis use for both conditions (β = -0.10, se=0.05, P = 0.026); CBTi-CB-TM participants demonstrated greater post-treatment reductions in the % of days cannabis was used within 2 h of bedtime (-29.1 ± 7.9 % fewer days vs. 2.6 ± 8.0 % more days, P = 0.008).

CONCLUSIONS

CBTi-CB-TM is feasible, acceptable, and demonstrated preliminary efficacy for improving sleep and cannabis-related outcomes among non-treatment-seeking individuals with regular cannabis use for sleep. Although sample characteristics limit generalizability, these findings support the need for adequately powered randomized controlled trials with longer follow-up periods.

Delta-8-THC association with psychosis: A case report with literature review

BACKGROUND

Cannabis (Δ⁹-THC) is the most commonly consumed illicit drug. The Agricultural Improvement Act of 2018 removed hemp, a strain of Cannabis sativa, as a controlled substance. This law allowed the plant to be processed into its components, which contain <0.3% Δ⁹-THC. As a result, delta-8-tetrahydrocannabinol (Δ⁸-THC), a federally unregulated substance, grew in popularity in 2020. Δ⁸-THC is readily available in most gas stations or head shops and may be considered harmless by patients. However, an increasing number of patients admitted for psychiatric hospitalization report use, with limited literature on the effects.

CASE PRESENTATIONS

This case report describes three individual cases of patients who required admission to a university psychiatric hospital after the regular use solely of Δ⁸-THC. All three patients developed psychotic and paranoid symptoms concurrently with the use of Δ⁸-THC, with a severity exceeding their previous historical presentations. The presenting psychotic symptoms were also atypical for all three patients. New-onset violence and visual hallucinations were noted in two of the patients, one patient with no previous psychiatric history and one patient while on a therapeutic dose of his antipsychotic. In the third case, a new onset of bizarre, fixed delusions of puppies dissolving in the bathtub developed.

CONCLUSION

This report adds to the limited body of evidence on Δ⁸-THC documenting a temporal association between Δ⁸-THC use and the development of psychotic symptoms. A strong body of research already correlates the continued use of Δ⁹-THC with psychosis, and Δ⁸-THC acts at the same CB₁ and CB₂ receptors as Δ⁹-THC. Therefore, it is hypothesized that Δ⁸-THC may have similar adverse psychiatric effects as Δ⁹-THC. These conclusions are not without speculation, due to the need for self or collateral-reporting of Δ⁸-THC use as urine drug screening cannot distinguish Δ⁸-THC from Δ⁹-THC, and the patients' symptoms could be explained by medication non-adherence and primary psychotic disorders. However, physicians should be encouraged to gather a specific history of Δ⁸-THC use and treat patients with Δ⁸-THC-related intoxication and symptoms.

Advancements in the development of multi-target directed ligands for the treatment of Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial irreversible neurological disorder which results in cognitive impairment, loss of cholinergic neurons in synapses of the basal forebrain and neuronal death. Exact pathology of the disease is not yet known however, many hypotheses have been proposed for its treatment. The available treatments including monotherapies and combination therapies are not able to combat the disease effectively because of its complex pathological mechanism. A multipotent drug for AD has the potential to bind or inhibit multiple targets responsible for the progression of the disease like aggregated Aβ, hyperphosphorylated tau proteins, cholinergic and adrenergic receptors, MAO enzymes, overactivated N-methyl-d-aspartate (NMDA), α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor etc. The traditional approach of one disease-one target-one drug has been rationalized to one drug-multi targets for the chronic diseases like AD and cancer. Thus, over the last decade research focus has been shifted towards the development of multi target directed ligands (MTDLs) which can simultaneously inhibit multiple targets and stop or slow the progression of the disease. The MTDLs can be more effective against AD and eliminate any possibility of drug-drug interactions. Many important active pharmacophore units have been fused, merged or incorporated into different scaffolds to synthesize new potent drugs. In the current article, we have described various hypothesis for AD and effectiveness of the MTDLs treatment strategy is discussed in detail. Different chemical scaffolds and their synthetic strategies have been described and important functionalities are identified in the chemical scaffold that have the potential to bind to the multiple targets. The important leads identified in this study with MTDL characteristics have the potential to be developed as drug candidates for the effective treatment of AD.

Levetiracetam-Induced Psychosis in the Setting of Intracranial Cavernomas

Levetiracetam is a commonly used antiepileptic medication that has been associated with the development of psychosis. Cavernomas are vascular malformations that have been associated with psychosis as well, especially in the setting of hemorrhagic transformation. This case report describes a patient with cavernomas who developed psychotic symptoms after restarting her levetiracetam at a high dose (2000 mg twice a day) without gradual uptitration. Her symptoms improved upon the reduction of the levetiracetam as well as the initiation of paliperidone. This case highlights the importance of considering the biologic and medication-related factors for the development of psychosis, as well as the importance of gradual medication adjustments.

Modulation of acute effects of delta-9-tetrahydrocannabinol on psychotomimetic effects, cognition and brain function by previous cannabis exposure

Cannabis use has been associated with psychosis and cognitive dysfunction. Some evidence suggests that the acute behavioral and neurocognitive effects of the main active ingredient in cannabis, (-)-trans-Δ9-tetrahydrocannabinol (∆9-THC), might be modulated by previous cannabis exposure. However, this has not been investigated either using a control group of non-users, or following abstinence in modest cannabis users, who represent the majority of recreational users. Twenty-four healthy men participated in a double-blind, randomized, placebo-controlled, repeated-measures, within-subject, ∆9-THC challenge study. Compared to non-users (N=12; <5 lifetime cannabis joints smoked), abstinent modest cannabis users (N=12; 24.5±9 lifetime cannabis joints smoked) showed worse performance and stronger right hemispheric activation during cognitive processing, independent of the acute challenge (all P≤0.047). Acute ∆9-THC administration produced transient anxiety and psychotomimetic symptoms (all P≤0.02), the latter being greater in non-users compared to users (P=0.040). Non-users under placebo (control group) activated specific brain areas to perform the tasks, while deactivating others. An opposite pattern was found under acute (∆9-THC challenge in non-users) as well as residual (cannabis users under placebo) effect of ∆9-THC. Under ∆9-THC, cannabis users showed brain activity patterns intermediate between those in non-users under placebo (control group), and non-users under ∆9-THC (acute effect) and cannabis users under placebo (residual effect). In non-users, the more severe the ∆9-THC-induced psychotomimetic symptoms and cognitive impairments, the more pronounced was the neurophysiological alteration (all P≤0.036). Previous modest cannabis use blunts the acute behavioral and neurophysiological effects of ∆9-THC, which are more marked in people who have never used cannabis.

Marijuana Use and Driving Under the Influence among Young Adults: A Socioecological Perspective on Risk Factors

BACKGROUND

Given increases in marijuana use and driving under the influence (DUI), it is critical to identify those at risk in order to inform intervention efforts.

OBJECTIVES

We used a socioecological framework to examine correlates of level of marijuana use and DUI in the past month among young adult marijuana users.

METHODS

We recruited 1567 participants aged 18-34 years via Facebook ads targeting tobacco and marijuana users in August 2014 to complete an online survey assessing marijuana use and DUI, as well as related multilevel factors. Analyses focused on 649 participants reporting past 30-day marijuana use.

RESULTS

The sample was an average age of 24.48 (SD = 5.10), 43.9% female, and 76.4% White and used marijuana an average of 17.86 (SD = 11.29) days in the past month. Notably, 48.4% reported driving after marijuana use at least once in the past month, and 74.0% were passengers. Multivariable regression indicated that greater use was associated with: being older; being male; greater symptoms of dependence; residing in a state with recreational marijuana legalized; having a medical marijuana card; having parents and more friends who use; higher coping motives; lower perceived harm to health; and less concern about driving after marijuana use (adjusted R-squared = 0.294). Correlates of driving after using marijuana in the past month included: being younger; more frequent use; having more friends who use; higher enhancement motives; and less concern about driving after using (Nagelkerke R-squared = 0.442). Conclusions/Importance: Interventions and campaigns should address social norms and risk perceptions regarding marijuana use, particularly as it relates to DUI.

The therapeutic potential of the phytocannabinoid cannabidiol for Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, characterized by progressive loss of cognition. Over 35 million individuals currently have AD worldwide. Unfortunately, current therapies are limited to very modest symptomatic relief. The brains of AD patients are characterized by the deposition of amyloid-β and hyperphosphorylated forms of tau protein. AD brains also show neurodegeneration and high levels of oxidative stress and inflammation. The phytocannabinoid cannabidiol (CBD) possesses neuroprotective, antioxidant and anti-inflammatory properties and reduces amyloid-β production and tau hyperphosphorylation in vitro. CBD has also been shown to be effective in vivo making the phytocannabinoid an interesting candidate for novel therapeutic interventions in AD, especially as it lacks psychoactive or cognition-impairing properties. CBD treatment would be in line with preventative, multimodal drug strategies targeting a combination of pathological symptoms, which might be ideal for AD therapy. Thus, this review will present a brief introduction to AD biology and current treatment options before outlining comprehensively CBD biology and pharmacology, followed by in-vitro and in-vivo evidence for the therapeutic potential of CBD. We will also discuss the role of the endocannabinioid system in AD before commenting on the potential future of CBD for AD therapy (including safety aspects).

Polyunsaturated fatty acids and endocannabinoids in health and disease

Polyunsaturated fatty acids (PUFAs) are lipid derivatives of omega-3 (docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA) or of omega-6 (arachidonic acid, ARA) synthesized from membrane phospholipids and used as a precursor for endocannabinoids (ECs). They mediate significant effects in the fine-tune adjustment of body homeostasis. Phyto- and synthetic cannabinoids also rule the daily life of billions worldwide, as they are involved in obesity, depression and drug addiction. Consequently, there is growing interest to reveal novel active compounds in this field. Cloning of cannabinoid receptors in the 90s and the identification of the endogenous mediators arachidonylethanolamide (anandamide, AEA) and 2-arachidonyglycerol (2-AG), led to the characterization of the endocannabinoid system (ECS), together with their metabolizing enzymes and membrane transporters. Today, the ECS is known to be involved in diverse functions such as appetite control, food intake, energy balance, neuroprotection, neurodegenerative diseases, stroke, mood disorders, emesis, modulation of pain, inflammatory responses, as well as in cancer therapy. Western diet as well as restriction of micronutrients and fatty acids, such as DHA, could be related to altered production of pro-inflammatory mediators (e.g. eicosanoids) and ECs, contributing to the progression of cardiovascular diseases, diabetes, obesity, depression or impairing conditions, such as Alzheimer' s disease. Here we review how diets based in PUFAs might be linked to ECS and to the maintenance of central and peripheral metabolism, brain plasticity, memory and learning, blood flow, and genesis of neural cells.

Synthetic Cannabinoid Use in a Psychiatric Patient Population: A Pilot Study

BACKGROUND

Consumption of natural cannabis (NC) and synthetic cannabinoids (SCs) has been associated with psychotic disorders. We compared the prevalence of use, consumer profiles, and psychosis-inducing potential of NC and SCs in a specific high-risk population.

METHODS

This prospective pilot study included 332 patients (18-64 years, mean 36.83, SD 13.33). Patients' sociodemographics and medical histories as well as illicit substance use and psychiatric symptom histories were collected using a drug consumption survey that assessed the use of new psychoactive substances and the Psychotic Symptoms Interview.

RESULTS

In total, 7.2% of all patients, 10.6% of psychotic patients, and 4.5% of nonpsychotic patients reported SC consumption. Compared with SCs, NC was consumed much more frequently by its users (mean 222.73, SD 498.27). NC and SC use induced persistent psychosis. Psychotic symptoms were first experienced by patients with a history of NC or SC use during intoxication and persisted after cessation (>1 year) of drug use. Positive and negative symptoms tended to be more severe in SC and NC users, respectively.

CONCLUSIONS

NC and SCs may cause different symptom clusters. These relationships should be further evaluated.

Differences in cannabis-related experiences between patients with a first episode of psychosis and controls

BACKGROUND

Many studies have reported that cannabis use increases the risk of a first episode of psychosis (FEP). However, only a few studies have investigated the nature of cannabis-related experiences in FEP patients, and none has examined whether these experiences are similar in FEP and general populations. The aim of this study was to explore differences in self-reported cannabis experiences between FEP and non-psychotic populations.

METHOD

A total of 252 subjects, who met International Classification of Diseases (ICD)-10 criteria for FEP, and 217 controls who reported cannabis use were selected from the Genetics and Psychosis (GAP) study. The Medical Research Council Social Schedule and the Cannabis Experience Questionnaire were used to collect sociodemographic data and cannabis use information, respectively.

RESULTS

Both 'bad' and 'enjoyable' experiences were more commonly reported by FEP subjects than controls. Principal components factor analysis identified four components which explained 62.3% of the variance. Linear regression analysis on the whole sample showed that the type of cannabis used and beliefs about the effect of cannabis on health all contributed to determining the intensity and frequency of experiences. Linear regression analysis on FEP subjects showed that the duration of cannabis use and amount of money spent on cannabis were strongly related to the intensity and frequency of enjoyable experiences in this population.

CONCLUSIONS

These results suggest a higher sensitivity to cannabis effects among people who have suffered their first psychotic episode; this hypersensitivity results in them reporting both more 'bad' and 'enjoyable' experiences. The greater enjoyment experienced may provide an explanation of why FEP patients are more likely to use cannabis and to continue to use it despite experiencing an exacerbation of their psychotic symptoms.

Long-term risk factors for substance-induced and primary psychosis after release from prison. A longitudinal study of substance users

PURPOSE

The purpose of this study was to determine long-term risk factors for substance-induced and primary psychosis after release from prison.

MATERIAL

We used a longitudinal register-based cohort study combining European version of Addiction Severity Index (Europ-ASI) interviews and the Swedish inpatient register. The study included 6217 individuals who were in the Swedish criminal justice system from 2001 to 2006.

MEASUREMENTS

The outcomes were substance-induced and primary psychosis as defined by the International Classification of Disease - 10th version. All variables for estimating baseline risk were drawn from the Europ-ASI interview, and included information on substance use, demographics and health. The interview database and the inpatient register were coupled, and groups were compared by using tests of significance and logistic regression.

RESULTS

Polydrug use was the strongest predictor for substance induced psychosis (OR=9.55, 95% CI 3.42-26.67), but all substances imposed an increased risk. Previous psychiatric hospitalization and non-drug related hallucinations were significant, but weaker, risk factors. The only substance variable that predicted primary psychosis was cannabis (OR=2.62, 95% CI 1.39-4.96), but previous psychiatric hospitalization (OR=3.22, 95% CI 2.27-4.54) and non-drug related hallucinations (OR=4.00, 95% CI 2.82-5.67) were even stronger predictors.

CONCLUSIONS

Cannabis use was a risk factor for primary psychosis, but other health related individual risk factors were even more important. Polydrug use was the strongest risk factor for substance-induced psychosis.

Drug models of schizophrenia

Schizophrenia is a complex mental health disorder with positive, negative and cognitive symptom domains. Approximately one third of patients are resistant to currently available medication. New therapeutic targets and a better understanding of the basic biological processes that drive pathogenesis are needed in order to develop therapies that will improve quality of life for these patients. Several drugs that act on neurotransmitter systems in the brain have been suggested to model aspects of schizophrenia in animals and in man. In this paper, we selectively review findings from dopaminergic, glutamatergic, serotonergic, cannabinoid, GABA, cholinergic and kappa opioid pharmacological drug models to evaluate their similarity to schizophrenia. Understanding the interactions between these different neurotransmitter systems and their relationship with symptoms will be an important step towards building a coherent hypothesis for the pathogenesis of schizophrenia.

The association between cannabis abuse and subsequent schizophrenia: a Swedish national co-relative control study

BACKGROUND

Although cannabis abuse (CA) is known to be associated with schizophrenia, the causal nature of this association is unclear, with prodromal effects complicating its interpretation.

METHOD

From Swedish national registry databases, we used a co-relative case-control design with full-sibling, half-sibling and first-cousin comparisons, alongside a general Swedish population sample. Using ICD codes, 5456 individuals with an initial diagnosis of schizophrenia (2000-2010) were matched with five schizophrenia-free controls. We further identified first-cousin, half-sibling and full-sibling pairs discordant for CA and statistically extrapolated results for discordant monozygotic (MZ) twins.

RESULTS

Within the general Swedish population, CA was strongly associated with later schizophrenia [odds ratio (OR) 10.44, 95% confidence interval (CI) 8.99-12.11]. This association was substantially attenuated both by increasing temporal delays between CA exposure and schizophrenia diagnosis and by controlling for increasing degrees of familial confounding. Extrapolated discordant MZ pairs suggested that fully controlling for confounding familial factors reduced the association between CA and later schizophrenia to more modest levels (ORs of approximately 3.3 and 1.6 with 3- and 7-year temporal delays respectively). Opiate, sedative, cocaine/stimulant and hallucinogen abuse were also strongly associated with subsequent schizophrenia in the general population. After controlling for familial confounding, only cocaine/stimulant exposure remained associated.

CONCLUSIONS

CA has an appreciable causal impact on future risk for schizophrenia. However, population-based estimates of cannabis-schizophrenia co-morbidity substantially overestimate their causal association. Predictions of the cases of schizophrenia that might be prevented by reduced cannabis consumption based on population associations are therefore likely to be considerably overestimated.

Characterizing cannabis-induced psychosis: a study with prepulse inhibition of the startle reflex

Cannabis-induced psychotic disorder (CIPD) refers to psychotic symptoms that arise in the context of cannabis intoxication. Prepulse inhibition (PPI) deficits have been extensively identified in schizophrenia and in cannabis abusers. We aimed to characterize PPI in CIPD patients. We used a sample of 48 CIPD patients, 54 schizophrenia patients and cannabis abuse (SCHZ), 44 cannabis dependents (CD), and 44 controls. CIPD, SCHZ and CD were abstinent of cannabis consumption for 9 months. Participants were assessed with PPI at 30, 60, and 120 ms. At 30 ms, CIPD showed lower PPI levels than controls, and SCHZ obtained worse functioning than controls and CD. At 60 ms, only SCHZ exhibited worse PPI percentages (of object) than controls. Finally, at 120 ms, CIPD showed higher PPI levels than SCHZ, and SCHZ obtained lower percentages than controls. We found that CIPD and SCHZ patients showed deficits at the most pre-attentional levels, whereas CIPD patients performed better than SCHZ at higher attentional levels. These results suggest that CIPD constitutes a different group of patients than that of SCHZ. Deficits in PPI functioning at 30 ms could be a useful psychophysiological measure to detect CIPD patients, who are frequently confused with cannabis abusers whose symptoms may mimic that of schizophrenia.

Effects of eye dominance (left vs. right) and cannabis use on intermanual coordination and negative symptoms in schizophrenia patients

Based on the previous findings, it has been assumed that in schizophrenia patients, eye dominance and cannabis use will affect negative symptoms and intermanual coordination (IMC), an index of interhemispheric communication. But eye dominance, specifically the clinical findings for it, has been neglected in schizophrenia research. We therefore investigated its effects in 52 right-handed (36 right-eyed and 16 left-eyed) and 51 left-handed (35 left-eyed and 16 right-eyed) schizophrenia in-patients without and with drug use. Eye dominance affected IMC in all schizophrenia patients. When comparing right- and left-handers, we found that this result was only significant in the right-handed patients and in the smaller subgroup without drug use. In the right-handers, left eye dominance-like left-handedness-was associated with higher values in IMC and less pronounced manifestation of negative symptoms, right eye dominance was not. Thus, left-eyed right-handers may be more closely related to left-handers than to right-handers. In accordance with the results from the literature, we suggest that these findings are due to better interhemispheric connections and less impairment of white matter structures, especially in right-hemispheric regions. Moreover, cannabis use was related to higher scores in IMC and less pronounced negative symptoms, but only in the right-eyed and not in the left-eyed right-handers or in the left-handers. Hence, differences in eye dominance and handedness may be partially responsible for different results in interhemispheric connections among cannabis users. In conclusion, both eye dominance and use of cannabis should be taken into account when assessing clinical symptoms in schizophrenia patients.

Impact of Cannabis Use on the Development of Psychotic Disorders

The link between cannabis use and psychosis comprises three distinct relationships: acute psychosis associated with cannabis intoxication, acute psychosis that lasts beyond the period of acute intoxication, and persistent psychosis not time-locked to exposure. Experimental studies reveal that cannabis, tetrahydrocannabinol (THC) and synthetic cannabinoids reliably produce transient positive, negative, and cognitive symptoms in healthy volunteers. Case-studies indicate that cannabinoids can induce acute psychosis which lasts beyond the period of acute intoxication but resolves within a month. Exposure to cannabis in adolescence is associated with a risk for later psychotic disorder in adulthood; this association is consistent, temporally related, shows a dose-response, and is biologically plausible. However, cannabis is neither necessary nor sufficient to cause a persistent psychotic disorder. More likely it is a component cause that interacts with other factors to result in psychosis. The link between cannabis and psychosis is moderated by age at onset of cannabis use, childhood abuse and genetic vulnerability. While more research is needed to better characterize the relationship between cannabinoid use and the onset and persistence of psychosis, clinicians should be mindful of the potential risk of psychosis especially in vulnerable populations, including adolescents and those with a psychosis diathesis.

Gone to Pot - A Review of the Association between Cannabis and Psychosis

Cannabis is the most commonly used illicit drug worldwide, with ~5 million daily users worldwide. Emerging evidence supports a number of associations between cannabis and psychosis/psychotic disorders, including schizophrenia. These associations-based on case-studies, surveys, epidemiological studies, and experimental studies indicate that cannabinoids can produce acute, transient effects; acute, persistent effects; and delayed, persistent effects that recapitulate the psychopathology and psychophysiology seen in schizophrenia. Acute exposure to both cannabis and synthetic cannabinoids (Spice/K2) can produce a full range of transient psychotomimetic symptoms, cognitive deficits, and psychophysiological abnormalities that bear a striking resemblance to symptoms of schizophrenia. In individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. Several factors appear to moderate these associations, including family history, genetic factors, history of childhood abuse, and the age at onset of cannabis use. Exposure to cannabinoids in adolescence confers a higher risk for psychosis outcomes in later life and the risk is dose-related. Individuals with polymorphisms of COMT and AKT1 genes may be at increased risk for psychotic disorders in association with cannabinoids, as are individuals with a family history of psychotic disorders or a history of childhood trauma. The relationship between cannabis and schizophrenia fulfills many but not all of the standard criteria for causality, including temporality, biological gradient, biological plausibility, experimental evidence, consistency, and coherence. At the present time, the evidence indicates that cannabis may be a component cause in the emergence of psychosis, and this warrants serious consideration from the point of view of public health policy.

Does Cannabidiol Protect Against Adverse Psychological Effects of THC?

The recreational use of cannabis can have persistent adverse effects on mental health. Delta-9-tetrahydrocannabinol (THC) is the main psychoactive constituent of cannabis, and most, if not all, of the effects associated with the use of cannabis are caused by THC. Recent studies have suggested a possible protective effect of another cannabinoid, cannabidiol (CBD). A literature search was performed in the bibliographic databases PubMed, PsycINFO, and Web of Science using the keyword "cannabidiol." After removing duplicate entries, 1295 unique titles remained. Based on the titles and abstracts, an initial selection was made. The reference lists of the publications identified in this manner were examined for additional references. Cannabis is not a safe drug. Depending on how often someone uses, the age of onset, the potency of the cannabis that is used and someone's individual sensitivity, the recreational use of cannabis may cause permanent psychological disorders. Most recreational users will never be faced with such persistent mental illness, but in some individuals cannabis use leads to undesirable effects: cognitive impairment, anxiety, paranoia, and increased risks of developing chronic psychosis or drug addiction. Studies examining the protective effects of CBD have shown that CBD can counteract the negative effects of THC. However, the question remains of how the laboratory results translate to the types of cannabis that are encountered by real-world recreational users.

Characteristics of adults seeking medical marijuana certification

BACKGROUND

Very little is known about medical marijuana users. The present study provides descriptive information on adults seeking medical marijuana and compares individuals seeking medical marijuana for the first time with those renewing their medical marijuana card on measures of substance use, pain and functioning.

METHODS

Research staff approached patients (n=348) in the waiting area of a medical marijuana certification clinic. Chi-square and Wilcoxon signed rank tests were used to compare participants who reported that they were seeking medical marijuana for the first time (n=195) and those who were seeking to renew their access to medical marijuana (n=153).

RESULTS

Returning medical marijuana patients reported a higher prevalence of lifetime cocaine, amphetamine, inhalant and hallucinogen use than first time patients. Rates of recent alcohol misuse and drug use were relatively similar between first time patients and returning patients with the exception of nonmedical use of prescription sedatives and marijuana use. Nonmedical prescription sedative use was more common among first time visitors compared to those seeking renewal (p<0.05). The frequency of recent marijuana use was higher in returning patients than first time patients (p<0.0001). Compared to first time patients, returning patients reported somewhat lower current pain level and slightly higher mental health and physical functioning.

CONCLUSIONS

Study results indicate that differences exist between first time and returning medical marijuana patients. Longitudinal data are needed to characterize trajectories of substance use and functioning in these two groups.

Novel Drugs of Abuse: A Snapshot of an Evolving Marketplace

BACKGROUND & OBJECTIVES

Over the past decade, non-medical use of novel drugs has proliferated worldwide. In most cases these are synthetic drugs first synthesized in academic or pharmaceutical laboratories for research or drug development purposes, but also include naturally occurring substances that do not fit the typical pharmacological or behavioral profile of traditional illicit substances. Perhaps most unique to this generation of new drugs is that they are being sold over the counter and on the Internet as "legal highs" or substitutes for traditional illicit drugs such as cannabis, cocaine, amphetamines, MDMA, and LSD. The purpose of this review is to provide an overview of novel drugs in current use, including the epidemiology of use and toxicologic and pharmacological properties, and to offer some guidelines to clinicians who see patients experiencing adverse effects from these drugs.

METHOD

We review the known scientific literature on recently introduced synthetic drug types, synthetic cannabinoids and synthetic cathinones, and the hallucinogen Salvia divinorum.

RESULTS

These substances comprise part of a rapidly evolving and controversial drug market that has challenged definitions of what is legal and illegal, has benefitted from open commercial sales without regulatory oversight, and is noteworthy for the pace at which new substances are introduced.

CONCLUSIONS

This emerging trend in substance use presents significant and unique public health and criminal justice challenges. At this time, these substances are not detected in routine drug screens and substance-specific treatment for cases of use-related toxicity are not available. Clinicians are encouraged to learn characteristic signs associated with misuse of novel drugs to recognize cases in their practice, and are recommended to use a symptom-specific approach for treatment in each case.

Amphetamine-induced psychosis--a separate diagnostic entity or primary psychosis triggered in the vulnerable?

Use of amphetamine and methamphetamine is widespread in the general population and common among patients with psychiatric disorders. Amphetamines may induce symptoms of psychosis very similar to those of acute schizophrenia spectrum psychosis. This has been an argument for using amphetamine-induced psychosis as a model for primary psychotic disorders. To distinguish the two types of psychosis on the basis of acute symptoms is difficult. However, acute psychosis induced by amphetamines seems to have a faster recovery and appears to resolve more completely compared to schizophrenic psychosis. The increased vulnerability for acute amphetamine induced psychosis seen among those with schizophrenia, schizotypal personality and, to a certain degree other psychiatric disorders, is also shared by non-psychiatric individuals who previously have experienced amphetamine-induced psychosis. Schizophrenia spectrum disorder and amphetamine-induced psychosis are further linked together by the finding of several susceptibility genes common to both conditions. These genes probably lower the threshold for becoming psychotic and increase the risk for a poorer clinical course of the disease.The complex relationship between amphetamine use and psychosis has received much attention but is still not adequately explored. Our paper reviews the literature in this field and proposes a stress-vulnerability model for understanding the relationship between amphetamine use and psychosis.

Alterations of theory of mind network activation in chronic cannabis users

Chronic cannabis use is associated with cognitive impairment and has been identified as a risk factor for schizophrenia. Patients with schizophrenia show profound deficits in social cognition such as the ability to attribute mental states to others, referred to as "theory of mind" (ToM). Aberrant activation of the ToM network has been demonstrated across different phases of schizophrenia, including at-risk stages. Accordingly, we aimed to investigate the ToM network in chronic cannabis users. Fifteen cannabis users received functional brain imaging during performance of a ToM cartoon story task. Findings were compared with 14 control subjects. Cannabis users showed less activation in the left parahippocampal gyrus, the right precuneus and cuneus, but greater activation in the left cuneus and the right anterior cingulate gyrus compared to healthy controls. These activation patterns resemble those found in at-risk populations, suggesting that cannabis use can affect the processing of social information similar to other risk factor constellations for psychosis.

New insights on endocannabinoid transmission in psychomotor disorders

The endocannabinoids are lipid signaling molecules that bind to cannabinoid CB(1) and CB(2) receptors and other metabotropic and ionotropic receptors. Anandamide and 2-arachidonoyl glycerol, the two best-characterized examples, are released on demand in a stimulus-dependent manner by cleavage of membrane phospholipid precursors. Together with their receptors and metabolic enzymes, the endocannabinoids play a key role in modulating neurotransmission and synaptic plasticity in the basal ganglia and other brain areas involved in the control of motor functions and motivational aspects of behavior. This mini-review provides an update on the contribution of the endocannabinoid system to the regulation of psychomotor behaviors and its possible involvement in the pathophysiology of Parkinson's disease and schizophrenia.

Cannabinoids and monoamine neurotransmission with focus on monoamine oxidase

Progress in understanding the mechanisms of action of cannabinoids was made after discovery of cannabinoid receptors and finding their endogenous ligands. New findings are obtained using both endogenous cannabinoids and plant or synthetic cannabinoids. Activation of cannabinoid receptors on synaptic terminals results in regulation of ion channels, neurotransmitter release and synaptic plasticity. Neuromodulation of synapses by cannabinoids is proving to have a wide range of functional effects, making them potential targets as medical preparations in a variety of illnesses, including some neurodegenerative and mental disorders. Brain monoamines are involved in many of the same processes affected by neuropsychiatric disorders and by different psychotropic drugs, including cannabinoids. Basic information is summarized in the paper about mechanisms of action of cannabinoids on monoaminergic systems, with a view to inhibition of monoamine oxidase.

Reversible and regionally selective downregulation of brain cannabinoid CB1 receptors in chronic daily cannabis smokers

Chronic cannabis (marijuana, hashish) smoking can result in dependence. Rodent studies show reversible downregulation of brain cannabinoid CB(1) (cannabinoid receptor type 1) receptors after chronic exposure to cannabis. However, whether downregulation occurs in humans who chronically smoke cannabis is unknown. Here we show, using positron emission tomography imaging, reversible and regionally selective downregulation of brain cannabinoid CB(1) receptors in human subjects who chronically smoke cannabis. Downregulation correlated with years of cannabis smoking and was selective to cortical brain regions. After ∼4 weeks of continuously monitored abstinence from cannabis on a secure research unit, CB(1) receptor density returned to normal levels. This is the first direct demonstration of cortical cannabinoid CB(1) receptor downregulation as a neuroadaptation that may promote cannabis dependence in human brain.

Effect of cannabis use on the course of schizophrenia in male patients: a prospective cohort study

BACKGROUND

Findings on the impact of cannabis use on the course of schizophrenia are inconsistent and not conclusive.

AIMS

To study the effect of cannabis use on the course of schizophrenia taking into account the effects of the quantity of cannabis use and important confounders.

METHODS

Prospective cohort study with assessments of symptoms, confounders and hospitalizations at baseline, 6 month and 12 month follow up.

RESULTS

In a representative cohort of 145 male patients with schizophrenia, 68 (46.9%) used cannabis. Mean age at onset of schizophrenia in cannabis using patients was significantly lower than in non-cannabis using patients. No other cross-sectional demographic or clinical differences were observed between users and non-users. In a series of longitudinal analyses, cannabis use was not associated with differences in psychopathology, but relapse in terms of the number of hospitalizations was significantly higher in cannabis using patients compared to non-cannabis using patients.

CONCLUSIONS

Patients with schizophrenia using cannabis are more frequently hospitalized than non-cannabis using patients but do not differ with respect to psychopathology. Possible explanations for these findings are discussed.

The therapeutic potential of the endocannabinoid system for Alzheimer's disease

INTRODUCTION

Dementia currently affects over 35 million people worldwide. The most common form of dementia is Alzheimer's disease (AD). Currently, treatments for AD do not stop or reverse the progression of the disease and they are accompanied by side effects.

AREAS COVERED

The main features of AD pathology, treatment options currently available, the endocannabinoid system and its functionality in general and its role in AD pathology in detail will be outlined. A particular focus will be on the therapeutic potential of the phytocannabinoid cannabidiol.

EXPERT OPINION

Based on the complex pathology of AD, a preventative, multimodal drug approach targeting a combination of pathological AD symptoms appears ideal. Importantly, cannabinoids show anti-inflammatory, neuroprotective and antioxidant properties and have immunosuppressive effects. Thus, the cannabinoid system should be a prime target for AD therapy. The cannabinoid receptor 2 appears to be a promising candidate but its role in AD has to be investigated cautiously. Furthermore, the phytocannabinoid cannabidiol is of particular interest as it lacks the psychoactive and cognition-impairing properties of other cannabinoids. In conclusion, future research should focus on the evaluation of the effects of manipulations to the endocannabinoid system in established animal models for AD, combined with early-phase studies in humans.

NMDA receptors, mGluR5, and endocannabinoids are involved in a cascade leading to hippocampal long-term depression

In the CA1 region of the rat hippocampus, metabotropic glutamate receptor-5 (mGluR5) and cannabinoid-1 receptors (CB1Rs) are believed to participate in long-term synaptic depression (LTD). How mGluRs and CB1Rs interact to promote LTD remains uncertain. In this study, we examined LTD induced by CB1R agonists, mGluR5 agonists, and low-frequency electrical stimulation (LFS) of the Schaffer collateral pathway. Synthetic CB1R agonists induced robust LTD that was mimicked by the endocannabinoid (EC), noladin ether (NLDE), but not by anandamide. 2-Arachidonylglycerol (2AG) produced only a small degree of LTD. The selective mGluR5 agonist, namely (RS)-2-chloro-5-hydroxyphenylglycine (CHPG), also induced robust LTD, and CHPG and NLDE occluded each other's effects. Similarly, CHPG and NLDE occluded LFS-induced LTD, and LTD resulting from all three treatments was blocked by a CB1R antagonist. CHPG-LTD and NLDE-LTD were insensitive to N-methyl-D-aspartate receptor (NMDAR) block, even though LFS-LTD requires NMDARs. LTD induced by LFS or CHPG, but not NLDE-LTD, was blocked by a selective mGluR5 antagonist. (RS)-3,5-dihydroxyphenylglycine (DHPG), a less selective group I mGluR agonist, also induced LTD, but its effects were not blocked by mGluR5 or CB1R antagonists. Furthermore, DHPG-LTD was additive with LFS-LTD and CHGP-LTD. These results suggest that NMDARs, mGluR5, and CB1Rs participate in a cascade that underlies LFS-LTD and that release of an EC and CB1R activation occur downstream of NMDARs and mGluR5. Furthermore, DHPG induces a form of LTD that differs mechanistically from LFS-induced depression.

Inhibition of cerebral type 1 cannabinoid receptors is associated with impaired auditory mismatch negativity generation in the ketamine model of schizophrenia

RATIONALE

Preclinical and clinical research suggests that the endogenous cannabinoid system is involved in cognitive impairments related to schizophrenia. In particular, the deficient generation of mismatch negativity (MMN) indicating auditory sensory memory is a characteristic finding in schizophrenic patients. Experimental studies implicate deficient N-methyl-D: -aspartate (NMDA) receptor functioning in such abnormalities.

OBJECTIVES

The primary aim of this study was to investigate the effects of the cannabinoid CB(1) receptor antagonist rimonabant on MMN deficits in the NMDA receptor antagonist model of schizophrenia by using ketamine.

METHODS

Twenty-four healthy male subjects participated in a randomized, double-blind, placebo-controlled cross-over study with subanesthetic doses of intravenous ketamine. The MMNs to frequency and duration deviants were elicited within an auditory oddball paradigm and recorded by a 32-channel EEG. Psychopathology was assessed using the Psychotomimetic States Inventory.

RESULTS

Twenty subjects completed both experimental sessions. Ketamine infusion had no significant effect on MMN amplitudes in both deviance conditions. In contrast to placebo, co-administration of rimonabant produced significant deficits in MMN amplitudes to duration deviants at electrode position Fz.

CONCLUSIONS

The results point to the involvement of the endogenous cannabinoid system in auditory sensory memory as a cognitive key feature in schizophrenia. They particularly suggest that CB(1) receptor antagonism may impair cognitive performance by a disturbed interaction between endocannabinergic activity and glutamatergic neurotransmission implied in schizophrenia.

Startle reactivity and prepulse inhibition in prodromal and early psychosis: effects of age, antipsychotics, tobacco and cannabis in a vulnerable population

The use of biomarkers in the study of the prodrome and first episode of psychosis provides a means of not only identifying individuals at greatest risk for psychosis but also understanding neurodevelopmental abnormalities early in the course of illness. Prepulse inhibition (PPI), a marker that is deficient in schizophrenia and after developmental manipulations in animal models, was assessed in 75 early psychosis (EP), 89 at risk (AR) for psychosis and 85 comparison subjects (CS) at baseline and 6 months. Consistent with findings in chronic schizophrenia, PPI was stable with repeated assessment and EP subjects had reduced PPI but this was most evident in tobacco smokers. A significant positive PPI and age association in AR and EP samples, but not CS, demonstrated potential neurodevelopmental differences in early psychosis. Unexpected findings included the fact that medication naive EP subjects, as well as AR subjects who later developed psychosis, had greater PPI, introducing the possibility of early compensatory changes that diverge from findings in chronic patients. In addition, subjects with a history of cannabis use had greater startle reactivity while EP and AR subjects who used cannabis and were also taking an antipsychotic had greater PPI, again highlighting the potentially important cannabis/psychosis association.

Schizophrenia, cancer and obstetric complications in an evolutionary perspective-an empirically based hypothesis

OBJECTIVE

Patients diagnosed with schizophrenia have reduced fecundity and premature mortality (both accidental and violent) with no obvious compensatory advantages among kin. The prevalence of the disorder is around 0.7/1%, higher than the expected prevalence of spontaneous mutations. Genes favoring schizophrenia may have been positively selected in the environment of evolutionary adaptation. Literature on potential adaptive genes is reviewed within an evolutionary framework.

METHODS

Literature search on major scientific search engine (PubMed/Medline, Ovid/PsychInfo) on papers aimed at investigating potential pathways justifying a mutation-selection balanced model. Findings are presented with a narrative touch to favor readability and understanding.

RESULTS

Reduced incidence of cancer in both patients diagnosed with schizophrenia and their siblings was reported worldwide. Such findings are notable given higher cancer risk factors in schizophrenia, i.e., smoking, alcohol abuse, obesity, poor diet, and poor adherence to therapy. Some genes involved in cancer proliferation might as well confer protective advantage in immune-surveillance, inflammation, vascular proliferation or apoptosis that otherwise will adversely affect early neurodevelopment.

CONCLUSION

Evidence that reduced risk of certain somatic diseases is associated with schizophrenia is quite significant to progress in the evolutionary epidemiological analysis of psychopathology.

Endocannabinoid modulation of hyperaemia evoked by physiologically relevant stimuli in the rat primary somatosensory cortex

BACKGROUND AND PURPOSE

In vitro studies demonstrate that cannabinoid CB(1) receptors subserve activity-dependent suppression of inhibition in the neocortex. To examine this mechanism in vivo, we assessed the effects of local changes in CB(1) receptor activity on somatosensory cortex neuronal activation by whisker movement in rats.

EXPERIMENTAL APPROACH

Laser Doppler flowmetry and c-Fos immunohistochemistry were used to measure changes in local blood flow and neuronal activation, respectively. All drugs were applied directly to the cranium above the whisker barrel fields of the primary somatosensory cortex.

KEY RESULTS

The CB(1) receptor agonist WIN55212-2 potentiated the hyperaemia induced by whisker movement and this potentiation was occluded by bicuculline. The CB(1) receptor antagonists, rimonabant and AM251, inhibited hyperaemic responses to whisker movement; indicating that activation of endogenous CB(1) receptors increased during whisker movement. Whisker movement-induced expression of c-Fos protein in neurons of the whisker barrel cortex was inhibited by rimonabant. Movement of the whiskers increased the 2-arachidonoylglycerol content in the contralateral, compared to the ipsilateral, sensory cortex.

CONCLUSIONS AND IMPLICATIONS

These results support the hypothesis that endocannabinoid signalling is recruited during physiologically relevant activation of the sensory cortex. These data support the hypothesis that the primary effect of CB(1) receptor activation within the activated whisker barrel cortex is to inhibit GABA release, resulting in disinhibition of neuronal activation. These studies provide physiological data involving endocannabinoid signalling in activity-dependent regulation of neuronal activation and provide a mechanistic basis for the effects of cannabis use on sensory processing in humans.

Auditory mismatch negativity deficits in long-term heavy cannabis users

Mismatch negativity (MMN) is an auditory event-related potential indicating auditory sensory memory and information processing. The present study tested the hypothesis that chronic cannabis use is associated with deficient MMN generation. MMN was investigated in age- and gender-matched chronic cannabis users (n = 30) and nonuser controls (n = 30). The cannabis users were divided into two groups according to duration and quantity of cannabis consumption. The MMNs resulting from a pseudorandomized sequence of 2 × 900 auditory stimuli were recorded by 32-channel EEG. The standard stimuli were 1,000 Hz, 80 dB SPL and 90 ms duration. The deviant stimuli differed in duration (50 ms) or frequency (1,200 Hz). There were no significant differences in MMN values between cannabis users and nonuser controls in both deviance conditions. With regard to subgroups, reduced amplitudes of frequency MMN at frontal electrodes were found in long-term (≥8 years of use) and heavy (≥15 joints/week) users compared to short-term and light users. The results indicate that chronic cannabis use may cause a specific impairment of auditory information processing. In particular, duration and quantity of cannabis use could be identified as important factors of deficient MMN generation.

Efeitos comportamentais, cognitivos e psicofisiológicos dos canabinoides: relevância para a psicose e a esquizofrenia

Avanços recentes no conhecimento sobre a função do receptor de canabinoide renovaram o interesse na associação entre cannabis e psicose. Linhas convergentes de evidências sugerem que os canabinoides podem produzir uma ampla gama de sintomas transitórios positivos, negativos e cognitivos assemelhados aos de esquizofrenia. Os canabinoides também produzem alguns déficits psicofisiológicos sabidamente presentes na esquizofrenia. É igualmente claro que em indivíduos com um transtorno psicótico estabelecido, os canabinoides podem exacerbar sintomas, desencadear recaídas e ter consequências negativas no curso da doença. Evidências crescentes sugerem que a exposição precoce e pesada à cannabis pode aumentar o risco de se desenvolver um transtorno psicótico como a esquizofrenia. A relação entre exposição à cannabis e esquizofrenia preenche alguns, mas não todos os critérios usuais de causalidade. Porém, a maioria das pessoas que utilizam cannabis não desenvolve esquizofrenia e muitas pessoas diagnosticadas com esquizofrenia nunca utilizaram cannabis. Portanto, é provável que a exposição à cannabis seja uma "causa componente" que interage com outros fatores para "causar" esquizofrenia ou outro transtorno psicótico, mas não é nem necessária nem suficiente para fazê-lo sozinha. No entanto, na ausência de causas conhecidas da esquizofrenia e com as implicações de políticas de saúde pública, se tal vínculo for estabelecido, as causas componentes, tais como a exposição a canabinoide, devem continuar sendo um foco de estudos futuros. Finalmente, são necessárias mais pesquisas para identificar os fatores subjacentes à vulnerabilidade à psicose relacionada a canabinoide e para elucidar os mecanismos biológicos subjacentes a esse risco.

Hyper-priming in cannabis users: a naturalistic study of the effects of cannabis on semantic memory function

Psychotic symptoms have theoretically been linked to semantic memory impairments in patients with schizophrenia. Little is known of the effects of cannabis, the world's most popular illicit drug, on semantic memory and whether they are linked to the psychotomimetic states elicited by the drug. Thirty-six cannabis users were tested whilst under the influence of cannabis. They were then tested again when not intoxicated and compared with 38 non-drug using controls. Semantic memory was assessed using a semantic priming task with a long and short stimulus onset asynchrony (SOA) to differentiate automatic and controlled processing. Under the influence of cannabis, users showed increases in both automatic semantic priming and schizotypal symptoms compared with controls. When abstinent, cannabis users exhibited hyper-priming at long SOAs. Cannabis users did not differ from controls in either trait schizotypy or state schizotypy when not intoxicated. Acute cannabis use increases schizotypyal symptoms and may increase automatic semantic priming in recreational users of this drug. When drug-free, cannabis users did not differ from controls in schizotypy but did show hyper-priming at the long SOA. The acute increase in automatic semantic priming may be one factor contributing to the psychotomimetic effects of cannabis.

Quantification of cerebral cannabinoid receptors subtype 1 (CB1) in healthy subjects and schizophrenia by the novel PET radioligand [11C]OMAR

Several studies have examined the link between the cannabinoid CB1 receptor and several neuropsychiatric illnesses, including schizophrenia. As such, there is a need for in vivo imaging tracers so that the relationship between CB1 and schizophrenia (SZ) can be further studied. In this paper, we present our first human studies in both healthy control patients and patients with schizophrenia using the novel PET tracer, [(11)C]OMAR (JHU75528), we have shown its utility as a tracer for imaging human CB1 receptors and to investigate normal aging and the differences in the cannabinoid system of healthy controls versus patients with schizophrenia. A total of ten healthy controls and nine patients with schizophrenia were included and studied with high specific activity [(11)C]OMAR. The CB1 binding (expressed as the distribution volume; V(T)) was highest in the globus pallidus and the cortex in both controls and patients with schizophrenia. Controls showed a correlation with the known distribution of CB1 and decline of [(11)C]OMAR binding with age, most significantly in the globus pallidus. Overall, we observed elevated mean binding in patients with schizophrenia across all regions studied, and this increase was statistically significant in the pons (p<0.05), by the Students t-test. When we ran a regression of the control subjects V(T) values with age and then compared the patient data to 95% prediction limits of the linear regression, three patients fell completely outside for the globus pallidus, and in all other regions there were at least 1-3 patients outside of the prediction intervals. There was no statistically significant correlations between PET measures and the individual Brief Psychiatry Rating Score (BPRS) subscores (r=0.49), but there was a significant correlation between V(T) and the ratio of the BPRS psychosis to withdrawal score in the frontal lobe (r=0.60), and middle and posterior cingulate regions (r=0.71 and r=0.79 respectively). In conclusion, we found that [(11)C] OMAR can image human CB1 receptors in normal aging and schizophrenia. In addition, our initial data in subjects with schizophrenia seem to suggest an association of elevated binding specific brain regions and symptoms of the disease.

Cannabinoid-dopamine interaction in the pathophysiology and treatment of CNS disorders

Endocannabinoids and their receptors, mainly the CB(1) receptor type, function as a retrograde signaling system in many synapses within the CNS, particularly in GABAergic and glutamatergic synapses. They also play a modulatory function on dopamine (DA) transmission, although CB(1) receptors do not appear to be located in dopaminergic terminals, at least in the major brain regions receiving dopaminergic innervation, e.g., the caudate-putamen and the nucleus accumbens/prefrontal cortex. Therefore, the effects of cannabinoids on DA transmission and DA-related behaviors are generally indirect and exerted through the modulation of GABA and glutamate inputs received by dopaminergic neurons. Recent evidence suggest, however, that certain eicosanoid-derived cannabinoids may directly activate TRPV(1) receptors, which have been found in some dopaminergic pathways, thus allowing a direct regulation of DA function. Through this direct mechanism or through indirect mechanisms involving GABA or glutamate neurons, cannabinoids may interact with DA transmission in the CNS and this has an important influence in various DA-related neurobiological processes (e.g., control of movement, motivation/reward) and, particularly, on different pathologies affecting these processes like basal ganglia disorders, schizophrenia, and drug addiction. The present review will address the current literature supporting these cannabinoid-DA interactions, with emphasis in aspects dealing with the neurochemical, physiological, and pharmacological/therapeutic bases of these interactions.

Inhibition of fatty-acid amide hydrolase and CB1 receptor antagonism differentially affect behavioural responses in normal and PCP-treated rats

The 'cannabinoid hypothesis' of schizophrenia tulates that over-activity of the endocannabinoid system might contribute to the aetiology of schizophrenia. In keeping with this hypothesis, increased expression of CB1 receptors, elevation of the endocannabinoid anandamide (AEA) and cannabinoid-induced cognitive changes have been reported in animal models of schizophrenia and psychotic patients. In this study we measured brain endocannabinoid levels and [35S]GTPgammaS binding stimulated by the CB receptor agonist CP55,940 in rats undergoing withdrawal from subchronic administration of phencyclidine (PCP), a well-established pharmacological model of schizophrenia. We also investigated whether systemic application of the fatty-acid amide hydrolase (FAAH) inhibitor URB597 or CB1 receptor blockade by AM251 affected the following PCP-induced behavioural deficits reminiscent of schizophrenia-like symptoms: (1) working-memory impairment (cognitive deficit), (2) social withdrawal (negative symptom), and (3) hyperactivity in response to d-amphetamine challenge (positive symptoms). PCP-treated rats showed increased endocannabinoid levels in the nucleus accumbens and ventral tegmental area, whereas CB1 receptor expression and CP55,940-stimulated [35S]GTPgammaS binding were unaltered. URB597 reversed the PCP-induced social withdrawal but caused social withdrawal and working-memory deficits in saline-treated rats that were comparable to those observed after PCP treatment. Administration of AM251 ameliorated the working-memory deficit in PCP-treated rats, but impaired working memory in saline-injected controls. Taken together, these results suggest that FAAH inhibition may improve negative symptoms in PCP-treated rats but produce deleterious effects in untreated animals, possibly by disturbing endocannabinoid tone. A similar pattern (beneficial for schizophrenia-related cognitive deficits, but detrimental under normal conditions) accompanies CB1 receptor blockade.

Cannabis and psychosis/schizophrenia: human studies

The association between cannabis use and psychosis has long been recognized. Recent advances in knowledge about cannabinoid receptor function have renewed interest in this association. Converging lines of evidence suggest that cannabinoids can produce a full range of transient schizophrenia-like positive, negative, and cognitive symptoms in some healthy individuals. Also clear is that in individuals with an established psychotic disorder, cannabinoids can exacerbate symptoms, trigger relapse, and have negative consequences on the course of the illness. The mechanisms by which cannabinoids produce transient psychotic symptoms, while unclear may involve dopamine, GABA, and glutamate neurotransmission. However, only a very small proportion of the general population exposed to cannabinoids develop a psychotic illness. It is likely that cannabis exposure is a "component cause" that interacts with other factors to "cause" schizophrenia or a psychotic disorder, but is neither necessary nor sufficient to do so alone. Nevertheless, in the absence of known causes of schizophrenia, the role of component causes remains important and warrants further study. Dose, duration of exposure, and the age of first exposure to cannabinoids may be important factors, and genetic factors that interact with cannabinoid exposure to moderate or amplify the risk of a psychotic disorder are beginning to be elucidated. The mechanisms by which exposure to cannabinoids increase the risk for developing a psychotic disorder are unknown. However, novel hypotheses including the role of cannabinoids on neurodevelopmental processes relevant to psychotic disorders are being studied.

Psychomotor performance in relation to acute oral administration of Delta9-tetrahydrocannabinol and standardized cannabis extract in healthy human subjects

Abnormalities in psychomotor performance are a consistent finding in schizophrenic patients as well as in chronic cannabis users. The high levels of central cannabinoid (CB(1)) receptors in the basal ganglia, the cerebral cortex and the cerebellum indicate their implication in the regulation of motor activity. Based on the close relationship between cannabis use, the endogenous cannabinoid system and motor disturbances found in schizophrenia, we expected that administration of cannabinoids may change pattern of psychomotor activity like in schizophrenic patients. This prospective, double-blind, placebo-controlled cross-over study investigated the acute effects of cannabinoids on psychomotor performance in 24 healthy right-handed volunteers (age 27.9 +/- 2.9 years, 12 male) by comparing Delta(9)-tetrahydrocannabinol (Delta(9)-THC) and standardized cannabis extract containing Delta(9)-THC and cannabidiol. Psychomotor performance was assessed by using a finger tapping test series. Cannabis extract, but not Delta(9)-THC, revealed a significant reduction of right-hand tapping frequencies that was also found in schizophrenia. As to the pure Delta(9)-THC condition, left-hand tapping frequencies were correlated with the plasma concentrations of the Delta(9)-THC metabolite 11-OH-THC. These effects are thought to be related to cannabinoid actions on CB(1) receptors in the basal ganglia, the cerebral cortex and the cerebellum. Our data further demonstrate that acute CB(1) receptor activation under the cannabis extract condition may also affect intermanual coordination (IMC) as an index of interhemispheric transfer. AIR-Scale scores as a measure of subjective perception of intoxication were dose-dependently related to IMC which was shown by an inverted U-curve. This result may be due to functional changes involving GABAergic and glutamatergic neurotransmission within the corpus callosum.

The adverse health effects of cannabis use: what are they, and what are their implications for policy?

BACKGROUND

The adverse health effects of cannabis are a source of contention in debates about policies towards the drug.

METHODS

This paper provides a review of epidemiological evidence on the major adverse health effects of cannabis use and considers its implications for policy.

RESULTS

The evidence strongly suggests that cannabis can adversely affect some users, especially adolescents who initiate use early and young adults who become regular users. These adverse effects probably include increased risks of: motor vehicle crashes, the development of cannabis dependence, impaired respiratory function, cardiovascular disease, psychotic symptoms, and adverse outcomes of adolescent development, namely, poorer educational outcomes and an increased likelihood of using other illicit drugs.

CONCLUSIONS

Politically, evidence of adverse health effects favours the status quo in developed countries like Australia where cannabis policy has been framed by the media as a choice between two views: (1) either cannabis use is largely harmless to most users and so we should legalize, or at the very least decriminalize its use; or (2) it harms some of its users so we should continue to prohibit its use.

Cannabinoids and psychosis

Recent advances in knowledge about cannabinoid receptor function have renewed interest in the association between cannabis and psychosis. Case series, autobiographical accounts, and surveys of cannabis users in the general population suggest an association between cannabis and psychosis. Cross-sectional studies document an association between cannabis use and psychotic symptoms, and longitudinal studies suggest that early exposure to cannabis confers a close to two-fold increase in the risk of developing schizophrenia. Pharmacological studies show that cannabinoids can induce a full range of transient positive, negative, and cognitive symptoms in healthy individuals that are similar to those seen in schizophrenia. There is considerable evidence that in individuals with an established psychotic disorder such as schizophrenia, exposure to cannabis can exacerbate symptoms, trigger relapse, and worsen the course of the illness. Only a very small proportion of the general population exposed to cannabis develop a psychotic illness. It is likely that cannabis exposure is a 'component cause' that interacts with other factors to 'cause' schizophrenia or other psychotic disorder, but is neither necessary nor sufficient to do so alone. Further work is necessary to identify the factors that underlie individual vulnerability to cannabinoid-related psychosis and to elucidate the biological mechanisms underlying this risk.

Cannabis use and age of diagnosis of schizophrenia

BACKGROUND AND OBJECTIVES

Observational studies have reported earlier onset of psychosis in schizophrenic patients with a history of cannabis use. Earlier age of onset of schizophrenia has been associated with a poorer outcome. We aimed to examine whether cannabis use determined an earlier onset of schizophrenia in a sample of first episode patients, in an area with one of Europe's highest rates of cannabis use.

METHODS

116 subjects with first episode psychosis and subsequent diagnosis of schizophrenia (after a 12-month follow-up) were included Age at first antipsychotic treatment (A1T) was used as proxy for age of psychosis onset, and acted as dependent variable for the statistical analysis. Cannabis use was evaluated retrospectively, and divided into three groups according to peak frequency (never, sporadic/frequent, daily).

RESULTS

46 (39.7%) subjects had never used cannabis, 23 (19.9%) had done so sporadically/frequently, and 47 (40.5%) daily. A1T differed between the three groups (mean, in years and [SD]: 27.0 [4.94]; 25.7 [4.44] and 24.5 [4.36]; p=0.033) and diminished as cannabis use increased (linear tendency; p=0.009). Post-hoc analysis showed that cannabis use (irrespective of frequency) was significantly associated with decrease in A1T (p=0.033), as shown by the first contrast [1 -1/2 -1/2]. Post-hoc contrast showed that cannabis users had a significantly lower age of onset of psychosis (mean decrease, in years: 1.93; CI (confidence interval) 95%: 0.17-3.70; p=0.033).

CONCLUSIONS

Cannabis use was significantly associated with a decrease in age of onset of schizophrenia. Age of onset of the disease correlated with frequency of cannabis use.

Blunted psychotomimetic and amnestic effects of delta-9-tetrahydrocannabinol in frequent users of cannabis

Cannabis is one of the most widely used illicit substances and there is growing interest in the association between cannabis use and psychosis. Delta-9-Tetrahydrocannabinol (Delta-9-THC) the principal active ingredient of cannabis has been shown to induce psychotomimetic and amnestic effects in healthy individuals. Whether people who frequently use cannabis are either protected from or are tolerant to these effects of Delta-9-THC has not been established. In a 3-day, double-blind, randomized, placebo-controlled study, the dose-related effects of 0, 2.5, and 5 mg intravenous Delta-9-THC were studied in 30 frequent users of cannabis and compared to 22 healthy controls. Delta-9-THC (1) produced transient psychotomimetic effects and perceptual alterations; (2) impaired memory and attention; (3) increased subjective effects of 'high'; (4) produced tachycardia; and (5) increased serum cortisol in both groups. However, relative to controls, frequent users showed blunted responses to the psychotomimetic, perceptual altering, cognitive impairing, anxiogenic, and cortisol increasing effects of Delta-9-THC but not to its euphoric effects. Frequent users also had lower prolactin levels. These data suggest that frequent users of cannabis are either inherently blunted in their response to, and/or develop tolerance to the psychotomimetic, perceptual altering, amnestic, endocrine, and other effects of cannabinoids.

The psychotomimetic states inventory (PSI): measuring psychotic-type experiences from ketamine and cannabis

BACKGROUND

This study reports a new measure of psychotomimetic states in the context of cannabis and ketamine use. The Psychotomimetic States Inventory (PSI) has sub-scales of Delusory Thinking, Perceptual Distortions, Cognitive Disorganization, Anhedonia, Mania and Paranoia.

METHODS

The PSI was administered in two independent group, repeated measures designs: an experimental study of ketamine and a naturalistic study of cannabis.

RESULTS

Both cannabis and ketamine produced reliable increases in ratings of psychotomimetic state effects across several sub-scales.

CONCLUSIONS

The PSI is a potentially useful measure of the nature and extent of the phenomenological effects of psychotropic drugs in schizophrenia-related research.