Lower negative symptom scores among cannabis-dependent patients with schizophrenia-spectrum disorders: preliminary evidence from an African American first-episode sample

Brexpiprazole in patients with schizophrenia with or without substance use disorder: an observational study

Background

Partial dopamine D2 receptor agonists are used for psychotic symptoms in adults with schizophrenia spectrum disorders. Recently, interest surged for partial dopamine D2 receptor agonists in substance use disorders (SUDs). Since it is believed that SUDs decrease the efficacy of pharmacotherapy of underlying psychiatric disorders, we tested the efficacy of the partial D2 agonist brexpiprazole in patients with schizophrenia who were either comorbid with a SUD (SUD group) or not comorbid (non-SUD) to assess treatment response and the effect of brexpiprazole on substance craving in SUD.

Methods

We included patients with DSM-5/DSM-5-TR schizophrenia (using SCID-5-CV) aged 18-66 years with either comorbid SUD or non-SUD to treat with brexpiprazole 4 mg/day for 6 months during February-October 2022. Patients were assessed with the Clinical Global Impressions-Severity (CGI-S) scale, the 24-item Brief Psychiatric Rating Scale (BPRS), and the Positive And Negative Syndrome Scale (PANSS) at baseline, weekly for the first 2 months and monthly for the next four. Furthermore, we assessed substance craving in SUD with a visual analog scale for craving (VAScrav) at the same timepoints.

Results

The total sample was 86 (85 analysable) 18- to 64-year-old (mean 39.32 ± 14.09) patients with schizophrenia [51 men (59.3%) and 35 women (40.7%)], of whom 48 SUD (55.8%) (37 men and 11 women) and 38 non-SUD (44.2%) (14 men and 24 women). No serious or persistent adverse events developed over the study period, but one patient dropped out for subjective akathisia. Results indicated the main effects of time with improvements over the course of the study for CGI-S, BPRS, and PANSS in both SUD and non-SUD groups and the entire sample, and for VAScrav in SUD. Brexpiprazole was associated with similar significant improvements in both groups at the 6 month endpoint compared to baseline.

Conclusion

Treatment with brexpiprazole for 6 months improved psychotic symptoms in patients with schizophrenia, independently from whether they belonged to the SUD or the non-SUD group; hence, SUD comorbidity did not confer treatment resistance to brexpiprazole. Furthermore, in the SUD group, we observed reduced substance craving.

Association between cannabis use and symptom dimensions in schizophrenia spectrum disorders: an individual participant data meta-analysis on 3053 individuals

Background

The association between cannabis use and positive symptoms in schizophrenia spectrum disorders is well documented, especially via meta-analyses. Yet, findings are inconsistent regarding negative symptoms, while other dimensions such as disorganization, depression, and excitement, have not been investigated. In addition, meta-analyses use aggregated data discarding important confounding variables which is a source of bias.

Methods

PubMed, ScienceDirect and PsycINFO were used to search for publications from inception to September 27, 2022. We contacted the authors of relevant studies to extract raw datasets and perform an Individual Participant Data meta-analysis (IPDMA). Inclusion criteria were: psychopathology of individuals with schizophrenia spectrum disorders assessed by the Positive and Negative Syndrome Scale (PANSS); cannabis-users had to either have a diagnosis of cannabis use disorder or use cannabis at least twice a week. The main outcomes were the PANSS subscores extracted via the 3-factor (positive, negative and general) and 5-factor (positive, negative, disorganization, depression, excitement) structures. Preregistration is accessible via Prospero: ID CRD42022329172.

Findings

Among the 1149 identified studies, 65 were eligible and 21 datasets were shared, totaling 3677 IPD and 3053 complete cases. The adjusted multivariate analysis revealed that relative to non-use, cannabis use was associated with higher severity of positive dimension (3-factor: Adjusted Mean Difference, aMD = 0.34, 95% Confidence Interval, CI = [0.03; 0.66]; 5-factor: aMD = 0.38, 95% CI = [0.08; 0.63]), lower severity of negative dimension (3-factor: aMD = -0.49, 95% CI [-0.90; -0.09]; 5-factor: aMD = -0.50, 95% CI = [-0.91; -0.08]), higher severity of excitement dimension (aMD = 0.16, 95% CI = [0.03; 0.28]). No association was found between cannabis use and disorganization (aMD = -0.13, 95% CI = [-0.42; 0.17]) or depression (aMD = -0.14, 95% CI = [-0.34; 0.06]).

Interpretation

No causal relationship can be inferred from the current results. The findings could be in favor of both a detrimental and beneficial effect of cannabis on positive and negative symptoms, respectively. Longitudinal designs are needed to understand the role of cannabis is this association. The reported effect sizes are small and CIs are wide, the interpretation of findings should be taken with caution.

Funding

This research did not receive any specific grant or funding. Primary financial support for authors was provided by Le Vinatier Psychiatric Hospital.

Neurobehavioral risk factors influence prevalence and severity of hazardous substance use in youth at genetic and clinical high risk for psychosis

Background

Elevated rates of alcohol, tobacco, and cannabis use are observed in both patients with psychotic disorders and individuals at clinical high risk for psychosis (CHR-P), and strong genetic associations exist between substance use disorders and schizophrenia. While individuals with 22q11.2 deletion syndrome (22qDel) are at increased genetic risk for psychosis, initial evidence suggests that they have strikingly low rates of substance use. In the current study, we aimed to directly compare substance use patterns and their neurobehavioral correlates in genetic and clinical high-risk cohorts.

Methods

Data on substance use frequency and severity, clinical symptoms, and neurobehavioral measures were collected at baseline and at 12-month follow-up visits in two prospective longitudinal cohorts: participants included 89 22qDel carriers and 65 age and sex-matched typically developing (TD) controls (40.67% male, Mage = 19.26 ± 7.84 years) and 1,288 CHR-P youth and 371 matched TD controls from the North American Prodrome Longitudinal Study-2 and 3 (55.74% male; Mage = 18.71 ± 4.27 years). Data were analyzed both cross-sectionally and longitudinally using linear mixed effects models.

Results

Controlling for age, sex, and site, CHR-P individuals had significantly elevated rates of tobacco, alcohol, and cannabis use relative to TD controls, whereas 22qDel had significantly lower rates. Increased substance use in CHR-P individuals was associated with increased psychosis symptom severity, dysphoric mood, social functioning, and IQ, while higher social anhedonia was associated with lower substance use across all domains at baseline. These patterns persisted when we investigated these relationships longitudinally over one-year. CHR-P youth exhibited significantly increased positive psychosis symptoms, dysphoric mood, social functioning, social anhedonia, and IQ compared to 22qDel carriers, and lower rates of autism spectrum disorder (ASD) compared to 22qDel carriers, both at baseline and at 1 year follow-up.

Conclusion

Individuals at genetic and CHR-P have strikingly different patterns of substance use. Factors such as increased neurodevelopmental symptoms (lower IQ, higher rates of ASD) and poorer social functioning in 22qDel may help explain this distinction from substance use patterns observed in CHR-P individuals.

Investigating repetitive transcranial magnetic stimulation on cannabis use and cognition in people with schizophrenia

Cannabis use disorder (CUD) occurs at high rates in schizophrenia, which negatively impacts its clinical prognosis. These patients have greater difficulty quitting cannabis which may reflect putative deficits in the dorsolateral prefrontal cortex (DLPFC), a potential target for treatment development. We examined the effects of active versus sham high-frequency (20-Hz) repetitive transcranial magnetic stimulation (rTMS) on cannabis use in outpatients with schizophrenia and CUD. Secondary outcomes included cannabis craving/withdrawal, psychiatric symptoms, cognition and tobacco use. Twenty-four outpatients with schizophrenia and CUD were enrolled in a preliminary double-blind, sham-controlled randomized trial. Nineteen participants were randomized to receive active (n = 9) or sham (n = 10) rTMS (20-Hz) applied bilaterally to the DLPFC 5x/week for 4 weeks. Cannabis use was monitored twice weekly. A cognitive battery was administered pre- and post-treatment. rTMS was safe and well-tolerated with high treatment retention (~90%). Contrast estimates suggested greater reduction in self-reported cannabis use (measured in grams/day) in the active versus sham group (Estimate = 0.33, p = 0.21; Cohen’s d = 0.72), suggesting a clinically relevant effect of rTMS. A trend toward greater reduction in craving (Estimate = 3.92, p = 0.06), and significant reductions in PANSS positive (Estimate = 2.42, p = 0.02) and total (Estimate = 5.03, p = 0.02) symptom scores were found in the active versus sham group. Active rTMS also improved attention (Estimate = 6.58, p < 0.05), and suppressed increased tobacco use that was associated with cannabis reductions (Treatment x Time: p = 0.01). Our preliminary findings suggest that rTMS to the DLPFC is safe and potentially efficacious for treating CUD in schizophrenia.

The endocannabinoid system as a therapeutic target for schizophrenia: Failures and potentials

Owing to its psychotropic effects, Cannabis has been stigmatized by its recreational use leading to a dramatic decline in the experimentations about its medical use in the twentieth century. The medical properties of the plant - known since ancient times - have received increased attention over recent years; yet, the research on its potential application in the field of psychiatry is still nascent. In this connection, the non-psychotropic cannabidiol (CBD) has emerged as a phytocannabinoid compound with promising antipsychotic effects. In addition, advances in our understanding of the endocannabinoid system, along with accumulating evidence implicating this system in the pathophysiology of schizophrenia, have stimulated research by the pharmaceutical industry to explore whether alteration of this system can be of medical benefit. This review examines the current state of evidence regarding the clinical potential of cannabinoid-based drugs as a treatment for schizophrenia, while discussing various limitations with the therapeutic approaches considered so far. In the second part, the author highlights the most promising strategies, as well as the most interesting directions one could follow, in the emerging field of cannabinoid therapies for schizophrenia.

Cannabis, schizophrenia genetic risk, and psychotic experiences: a cross-sectional study of 109,308 participants from the UK Biobank

Cannabis is known to produce acute, transient psychotic-like experiences. However, it is unclear whether cannabis disproportionately increases the risk of specific types of psychotic experiences and whether genetic predisposition influences the relationship between cannabis use and psychotic experiences. In this cross-sectional study of 109,308 UK Biobank participants, we examined how schizophrenia polygenic risk modulates the association between self-reported cannabis use and four types of self-reported psychotic experiences (auditory hallucinations, visual hallucinations, persecutory delusions, and delusions of reference). Cohort-wide, we found a strong, dose-dependent relationship between cannabis use and all four types of psychotic experiences, especially persecutory delusions. Cannabis users' psychotic experiences tended to be earlier-onset and cause greater distress than non-users', but were not more likely to lead to help-seeking. Participants with high schizophrenia polygenic risk scores showed stronger associations between cannabis use and auditory hallucinations, visual hallucinations, and delusions of reference, as well as psychotic experiences overall. For instance, cannabis ever-use was associated with 67% greater adjusted odds of delusions of reference among individuals in the top fifth of polygenic risk, but only 7% greater adjusted odds among the bottom fifth. Our results suggest that cannabis use is a predictive risk factor for psychotic experiences, including early-onset and distressing experiences. Individuals genetically predisposed to schizophrenia may be especially vulnerable to psychotic experiences as a result of using cannabis, supporting a long-postulated hypothesis. This study exemplifies the utility of population-scale biobanks for elucidating gene-by-environment interactions relating substance use to neuropsychiatric outcomes and points to the translational potential of using polygenic risk scores to inform personalized harm reduction interventions.

Kynurenines and the Endocannabinoid System in Schizophrenia: Common Points and Potential Interactions

Schizophrenia, which affects around 1% of the world’s population, has been described as a complex set of symptoms triggered by multiple factors. However, the exact background mechanisms remain to be explored, whereas therapeutic agents with excellent effectivity and safety profiles have yet to be developed. Kynurenines and the endocannabinoid system (ECS) play significant roles in both the development and manifestation of schizophrenia, which have been extensively studied and reviewed previously. Accordingly, kynurenines and the ECS share multiple features and mechanisms in schizophrenia, which have yet to be reviewed. Thus, the present study focuses on the main common points and potential interactions between kynurenines and the ECS in schizophrenia, which include (i) the regulation of glutamatergic/dopaminergic/γ-aminobutyric acidergic neurotransmission, (ii) their presence in astrocytes, and (iii) their role in inflammatory mechanisms. Additionally, promising pharmaceutical approaches involving the kynurenine pathway and the ECS will be reviewed herein.

Astrocytic Mechanisms Involving Kynurenic Acid Control Δ9-Tetrahydrocannabinol-Induced Increases in Glutamate Release in Brain Reward-Processing Areas

The reinforcing effects of Δ⁹-tetrahydrocannabinol (THC) in rats and monkeys, and the reinforcement-related dopamine-releasing effects of THC in rats, can be attenuated by increasing endogenous levels of kynurenic acid (KYNA) through systemic administration of the kynurenine 3-monooxygenase inhibitor, Ro 61-8048. KYNA is a negative allosteric modulator of α7 nicotinic acetylcholine receptors (α7nAChRs) and is synthesized and released by astroglia, which express functional α7nAChRs and cannabinoid CB1 receptors (CB1Rs). Here, we tested whether these presumed KYNA autoreceptors (α7nAChRs) and CB1Rs regulate glutamate release. We used in vivo microdialysis and electrophysiology in rats, RNAscope in situ hybridization in brain slices, and primary culture of rat cortical astrocytes. Acute systemic administration of THC increased extracellular levels of glutamate in the nucleus accumbens shell (NAcS), ventral tegmental area (VTA), and medial prefrontal cortex (mPFC). THC also reduced extracellular levels of KYNA in the NAcS. These THC effects were prevented by administration of Ro 61-8048 or the CB1R antagonist, rimonabant. THC increased the firing activity of glutamatergic pyramidal neurons projecting from the mPFC to the NAcS or to the VTA in vivo. These effects were averted by pretreatment with Ro 61-8048. In vitro, THC elicited glutamate release from cortical astrocytes (on which we demonstrated co-localization of the CB1Rs and α7nAChR mRNAs), and this effect was prevented by KYNA and rimonabant. These results suggest a key role of astrocytes in interactions between the endocannabinoid system, kynurenine pathway, and glutamatergic neurotransmission, with ramifications for the pathophysiology and treatment of psychiatric and neurodegenerative diseases.

Clinical characteristics of primary psychotic disorders with concurrent substance abuse and substance-induced psychotic disorders: A systematic review

BACKGROUND

Distinguishing between a primary psychotic disorder with concurrent substance abuse (PPD+SA) and a substance-induced psychotic disorder (SIPD) can be diagnostically challenging. We aimed to determine if these two diagnoses are clinically distinct, particularly in relation to psychopathology. In addition, we aimed to examine the specific clinical features of cannabis-induced psychotic disorder (CIPD) as compared to primary psychotic disorder with concurrent cannabis abuse (PPD+CA) and also to SIPD associated with any substance.

METHODS

A systematic review of SIPD literature using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Using strict inclusion criteria, a total of six studies examining SIPD were included in the review (two of which only considered psychosis induced by cannabis alone). The findings did not reveal many consistent differences in psychopathology. However, we did find that that compared to PPD+SA, individuals with SIPD have a weaker family history of psychotic disorder; a greater degree of insight; fewer positive symptoms and fewer negative symptoms; more depression (only in CIPD) and more anxiety.

CONCLUSION

There remains a striking paucity of information on the psychopathology, clinical characteristics and outcome of SIPD. Our review highlights the need for further research in this area.

[Negative symptoms in schizophrenia and substance-related disorders]

Dual diagnosis of schizophrenia and substance-related disorders is common in psychiatric practice. Epidemiologic studies and report have established that the risk of a substance-related disorder was 4 to 5 times higher in a population of psychiatric patients than in the general population. However, little is known on the reason of this relationship and the treatments required. It's well known that a family history of psychosis is a risk factor of schizophrenia. Similarly a family history of substance use disorders increases the risk of using substances. Because the two disorders often occurred together, it could be hypothesized that a genetic risk factor is common. However, recent studies did not confirm this hypothesis and it seems that their genetic risks factor would be unrelated. Evidence now exists describing the different profiles of patients whether they used substance or not. Concerning negative symptoms clinical studies and meta-analyses have described fewer symptoms in schizophrenia patients with a substance use disorder. Among the different explanations that have been addressed, it seems that a lower capability of obtaining the substance could partly explain this relationship. Perhaps because patients with social withdrawal have more difficulties to find and spend the time required to obtain abused substances. At the opposite some products such as cocaine may relieve some symptoms especially anhedonia and alogia. However the link between substance-related disorders and negative symptoms is weak and decreases in more recent studies, probably because negative symptoms as well as addiction disorders are better characterized. Considering that treating psychiatric symptoms may not always lead to a decrease in the substance-related disorders but that patients who give up substances improve their psychotic symptoms, a therapeutic strategy should be planned for these dual disorders patients combining psychiatry and addiction interventions.

Cannabis Use and Associated Harms among Schizophrenia Patients in a Nigerian Clinical Setting: A Case-Control Study

AIM

The overall aim of this study was to determine the prevalence of cannabis use among patients with schizophrenia with associated levels of harm in a Nigerian clinical setting.

METHOD

In this case-control study, consecutive 150 patients with schizophrenia were matched by age and gender with an equal number of patients that utilized the general outpatient department of the State Hospital, Ring Road Ibadan. The alcohol, smoking and substance involvement screening test (ASSIST) was used to obtain prevalence of cannabis use and level of health risk as determined by the ASSIST score. The positive and negative syndrome scale was used to determine the severity of psychosis.

RESULTS

Prevalence of cannabis use among the cases and control group was 10.0 and 2.7%, respectively, p = 0.03. Mean ASSIST score was significantly higher among the cases compared with the control, p < 0.001. Respondents of male gender and those who were not married were significantly more likely to be cannabis users among patients with schizophrenia (p < 0.001 and p < 0.02), respectively.

CONCLUSION

Cannabis use was prevalent among patients with schizophrenia and was associated with health risks. Thus, routine screening for cannabis use and brief intervention is suggested to be integrated into care for adolescents and adults with schizophrenia.

A clinical comparison of schizophrenia with and without pre-onset cannabis use disorder: a retrospective cohort study using categorical and dimensional approaches

BACKGROUND

A high prevalence of cannabis use disorder has been reported in subjects suffering from schizophrenia, fuelling intense debate about whether schizophrenia with pre-onset cannabis use disorder may be a distinct entity with specific features or whether cannabis use disorder can precipitate schizophrenia in genetically vulnerable subjects.

METHODS

We retrospectively assessed schizophrenia subjects with and without pre-onset cannabis use disorder on the basis of their clinical features, assessed categorically and dimensionally with the operational criteria checklist for psychotic illnesses (OCCPI). We also investigated whether the two groups could be differentiated on the basis of a history of psychiatric disorders in first-degree relatives. A principal component factor analysis of the OCCPI items was used to identify specific symptom dimensions. The relationships between symptom dimensions and cannabis status were analysed by point-biserial correlation analysis to control for sex and age at time of the assessment and illness duration.

RESULTS

One hundred and seventy-one subjects with a diagnosis of schizophrenia were included. Among them, forty-one patients (18.2 % of the sample) had a cannabis use disorder before or at the time of the onset of schizophrenia. We found similar results in symptoms patterns or family history between patients with and without pre-onset cannabis use disorder.

CONCLUSIONS

Our results clearly argue against cannabis-associated schizophrenia being a relevant distinct clinical entity of schizophrenia with specific features.

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.

Genetic predisposition to schizophrenia associated with increased use of cannabis

Cannabis is the most commonly used illicit drug worldwide. With debate surrounding the legalization and control of use, investigating its health risks has become a pressing area of research. One established association is that between cannabis use and schizophrenia, a debilitating psychiatric disorder affecting ~1% of the population over their lifetime. Although considerable evidence implicates cannabis use as a component cause of schizophrenia, it remains unclear whether this is entirely due to cannabis directly raising risk of psychosis, or whether the same genes that increases psychosis risk may also increase risk of cannabis use. In a sample of 2082 healthy individuals, we show an association between an individual's burden of schizophrenia risk alleles and use of cannabis. This was significant both for comparing those who have ever versus never used cannabis (P=2.6 × 10(-4)), and for quantity of use within users (P=3.0 × 10(-3)). Although directly predicting only a small amount of the variance in cannabis use, these findings suggest that part of the association between schizophrenia and cannabis is due to a shared genetic aetiology. This form of gene-environment correlation is an important consideration when calculating the impact of environmental risk factors, including cannabis use.

Stress-induced dopamine response in subjects at clinical high risk for schizophrenia with and without concurrent cannabis use

Research on the environmental risk factors for schizophrenia has focused on either psychosocial stress or drug exposure, with limited investigation of their interaction. A heightened dopaminergic stress response in patients with schizophrenia and individuals at clinical high risk (CHR) supports the dopaminergic sensitization hypothesis. Cannabis is believed to contribute to the development of schizophrenia, possibly through a cross-sensitization with stress. Twelve CHR and 12 cannabis-using CHR (CHR-CU, 11 dependent) subjects underwent [(11)C]-(+)-PHNO positron emission tomography scans, while performing a Sensorimotor Control Task (SMCT) and a stress condition (Montreal Imaging Stress task). The simplified reference tissue model was used to obtain binding potential relative to non-displaceable binding (BPND) in the whole striatum, its functional subdivisions (limbic striatum (LST), associative striatum (AST), and sensorimotor striatum (SMST)), globus pallidus (GP), and substantia nigra (SN). Changes in BPND, reflecting alterations in synaptic dopamine (DA) levels, were tested with analysis of variance. SMCT BPND was not significantly different between groups in any brain region (p>0.21). Although stress elicited a significant reduction in BPND in the CHR group, CHR-CU group exhibited an increase in BPND. Stress-induced changes in regional BPND between CHR-CU and CHR were significantly different in AST (p<0.001), LST (p=0.007), SMST (p=0.002), SN (p=0.021), and whole striatum (p=0.001), with trend level in the GP (p=0.099). All subjects experienced an increase in positive (attenuated) psychotic symptoms (p=0.001) following the stress task. Our results suggest altered DA stress reactivity in CHR subjects who concurrently use cannabis, as compared with CHR subjects. Our finding does not support the cross-sensitization hypothesis, which posits greater dopaminergic reactivity to stress in CHR cannabis users, but adds to the growing body of literature showing reduced DA (stress) response in addiction.

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 substance use disorder affect clinical expression in first-hospitalization patients with schizophrenia? Analysis of a prospective cohort

Although several papers reported a wide range of negative outcomes among patients with both schizophrenia and Substance Use Disorder (SUD), only a few studies evaluated the impact of SUD on psychopathology and thus on the length of first-hospitalization. The aim of the present study was to compare clinical expression of first-episode of schizophrenia between inpatients with and without SUD, giving close attention to the length of stay. One hundred and thirty inpatients at first-episode of schizophrenia were assigned to either SUD or not SUD group depending on SUD diagnosis and were assessed through BPRS at admission, during hospitalization and at discharge. Cross-sectional and longitudinal statistical analysis were performed to investigate differences between groups and also a linear regression was used to evaluate relationship between length of stay and BPRS scores. SUD group showed more disorganization at admission, less marked improvement of symptoms (disorganization, thought disturbance, anergia), and longer hospital stay than not SUD group. Moreover BPRS total score during hospitalization was a significant positive predictor for length of stay. Taken together, these findings suggest that SUD patients have a more severe and drug-resistant expression of schizophrenia, hence, they need longer treatment to achieve the overall symptoms improvement required for discharge.

Pathways from cannabis to psychosis: a review of the evidence

The nature of the relationship between cannabis use (CU) and psychosis is complex and remains unclear. Researchers and clinicians remain divided regarding key issues such as whether or not cannabis is an independent cause of psychosis and schizophrenia. This paper reviews the field in detail, examining questions of causality, the neurobiological basis for such causality and for differential inter-individual risk, the clinical and cognitive features of psychosis in cannabis users, and patterns of course and outcome of psychosis in the context of CU. The author proposes two major pathways from cannabis to psychosis based on a differentiation between early-initiated lifelong CU and a scenario where vulnerable individuals without a lifelong pattern of use consume cannabis over a relatively brief period of time just prior to psychosis onset. Additional key factors determining the clinical and neurobiological manifestation of psychosis as well as course and outcome in cannabis users include: underlying genetic and developmental vulnerability to schizophrenia-spectrum disorders; and whether or not CU ceases or continues after the onset of psychosis. Finally, methodological guidelines are presented for future research aimed at both elucidating the pathways that lead from cannabis to psychosis and clarifying the long-term outcome of the disorder in those who have a history of using cannabis.

Phencyclidine-induced social withdrawal results from deficient stimulation of cannabinoid CB₁ receptors: implications for schizophrenia

The neuronal mechanisms underlying social withdrawal, one of the core negative symptoms of schizophrenia, are not well understood. Recent studies suggest an involvement of the endocannabinoid system in the pathophysiology of schizophrenia and, in particular, of negative symptoms. We used biochemical, pharmacological, and behavioral approaches to investigate the role played by the endocannabinoid system in social withdrawal induced by sub-chronic administration of phencyclidine (PCP). Pharmacological enhancement of endocannabinoid levels via systemic administration of URB597, an inhibitor of endocannabinoid degradation, reversed social withdrawal in PCP-treated rats via stimulation of CB1 receptors, but reduced social interaction in control animals through activation of a cannabinoid/vanilloid-sensitive receptor. In addition, the potent CB agonist CP55,940 reversed PCP-induced social withdrawal in a CB₁-dependent manner, whereas pharmacological blockade of CB₁ receptors by either AM251 or SR141716 reduced the time spent in social interaction in control animals. PCP-induced social withdrawal was accompanied by a decrease of anandamide (AEA) levels in the amygdala and prefrontal cortex, and these deficits were reversed by URB597. As CB₁ receptors are predominantly expressed on GABAergic interneurons containing the anxiogenic peptide cholecystokinin (CCK), we also examined whether the PCP-induced social withdrawal resulted from deficient CB₁-mediated modulation of CCK transmission. The selective CCK2 antagonist LY225910 blocked both PCP- and AM251-induced social withdrawal, but not URB597 effect in control rats. Taken together, these findings indicate that AEA-mediated activation of CB₁ receptors is crucial for social interaction, and that PCP-induced social withdrawal results from deficient endocannabinoid transmission.

A multi-center, randomized controlled trial of a group psychological intervention for psychosis with comorbid cannabis dependence over the early course of illness

BACKGROUND

Patients who experience the onset of psychotic illness with a comorbid diagnosis of cannabis dependence experience poor clinical outcomes. Few studies have identified interventions that reduce cannabis use and improve clinical outcome in this population.

AIMS

We undertook a multi-center, randomized controlled trial of a group psychological intervention for psychosis with comorbid cannabis dependence to determine whether there was any impact on cannabis use symptoms, global functioning, insight, attitudes to treatment and subjective quality of life.

METHOD

Across three centers, we compared a group psychological intervention, based on cognitive behavioral therapy and motivational interviewing, with treatment as usual among patients experiencing their first psychotic episode or early in the course of psychotic illness. Substance misuse and indices of clinical outcome were assessed at baseline, 3months and 1year.

RESULTS

At 3month and 1year follow-ups, there was no evidence for an intervention effect on cannabis use, symptoms, global functioning insight or attitude to treatment. However, the intervention improved subjective quality of life at 3months and this effect was sustained at 1year.

CONCLUSIONS

Over the early phase of psychotic illness, group psychological interventions for those with comorbid cannabis dependence improved subjective quality of life. However, this was not associated with reduction in use of cannabis or improvement in clinical outcomes.

A 10-year study of steady employment and non-vocational outcomes among people with serious mental illness and co-occurring substance use disorders

OBJECTIVE

Employment promotes recovery for persons with serious mental illness by providing extra income and a valued social role, but the impact of employment on other psychosocial and clinical outcomes remains unclear. This study examined non-vocational outcomes in relation to steady employment over 10 years among people with serious mental illness and co-occurring substance use disorders.

METHODS

Researchers interviewed people with co-occurring disorders at baseline and yearly for 10 years and tracked employment in relation to five non-vocational outcomes: independent living, psychiatric symptoms, substance use disorder, healthy (non-substance-abusing) relationships, and life satisfaction. Latent class trajectory analysis identified steady workers, and mixed-effects regression models compared steady workers with non-workers.

RESULTS

Both steady workers (n=51) and non-workers (n=79) improved substantially; for example, a majority of each group achieved independent housing and stable remission of substance use disorders. Steady workers achieved independent housing and higher quality of life during the first 5 years of follow-up, but the two groups achieved similar outcomes by 10 years.

CONCLUSIONS

People with co-occurring disorders can improve markedly. Those with steady employment may improve faster, but those without employment may achieve similar long-term outcomes at a slower pace.

Cannabis use and psychosis: re-visiting the role of childhood trauma

BACKGROUND

Cannabis consumption continues to be identified as a causal agent in the onset and development of psychosis. However, recent findings have shown that the effect of cannabis on psychosis may be moderated by childhood traumatic experiences.

METHOD

Using hierarchical multivariate logistic analyses the current study examined both the independent effect of cannabis consumption on psychosis diagnosis and the combined effect of cannabis consumption and childhood sexual abuse on psychosis diagnosis using data from the Adult Psychiatric Morbidity Survey 2007 (n=7403).

RESULTS

Findings suggested that cannabis consumption was predictive of psychosis diagnosis in a bivariate model; however, when estimated within a multivariate model that included childhood sexual abuse, the effect of cannabis use was attenuated and was not statistically significant. The multivariate analysis revealed that those who had experienced non-consensual sex in childhood were over six times [odds ratio (OR) 6.10] more likely to have had a diagnosis of psychosis compared with those who had not experienced this trauma. There was also a significant interaction. Individuals with a history of non-consensual sexual experience and cannabis consumption were over seven times more likely (OR 7.84) to have been diagnosed with psychosis compared with those without these experiences; however, this finding must be interpreted with caution as it emerged within an overall analytical step which was non-significant.

CONCLUSIONS

Future studies examining the effect of cannabis consumption on psychosis should adjust analyses for childhood trauma. Childhood trauma may advance existing gene-environment conceptualisations of the cannabis-psychosis link.

Differential effects of chronic cannabis use on preattentional cognitive functioning in abstinent schizophrenic patients and healthy subjects

INTRODUCTION

A number of studies indicate a higher risk for psychosis as well as for neurocognitive deficits in healthy cannabis users. However, little is known about the impact of cannabis use on outcome in schizophrenia. In fact, there is growing evidence that cannabis-using schizophrenic patients may show preserved or even better neurocognitive performance compared to schizophrenic non-users.

METHODS

We measured mismatch negativity (MMN) to investigate preattentional neurocognitive functioning in long-term abstinent chronic cannabis users with (SZCA n=27) and without schizophrenia (COCA n=32) compared to schizophrenic patients (SZ n=26) and healthy controls (CO n=34) without any chronic drug use.

RESULTS

Healthy cannabis users showed reduced frontal MMN compared to controls (p=0.036). In contrast, cannabis-using schizophrenic patients showed increased frontal MMN compared to schizophrenic patients without cannabis use (p=0.038). Comparing non-cannabis users, schizophrenic patients showed reduced frontal MMN (p=0.001). No significant differences were found between CO and SZCA (p=0.27), and COCA and SZCA (p=0.50).

CONCLUSION

Results suggest that chronic cannabis use may have different effects on preattentional neurocognitive functioning in schizophrenic patients when compared to healthy subjects. This may be related to preexisting differences in the endocannabinoid system between schizophrenic patients and healthy subjects. However, due to the naturalistic design of the study, the results must be interpreted with caution.

Cannabis use and striatal D2 receptor density in untreated first-episode psychosis: an in vivo SPECT study

The biological basis of the association between cannabis-induced dopamine dysregulation and psychosis remains poorly understood. This (123)I-IBZM SPECT study assessed striatal dopamine D2 receptor (D2R) binding in 37 untreated first-episode psychosis (FEP) subjects, and 18 healthy controls. The aim was to examine if there were differences between FEP subjects with (n=14) and without (n=23) cannabis use in uptake ratios in the D2R. Striatal/Frontal cortex (S/F) uptake ratios were obtained. Healthy controls showed the lowest D2R binding ratios. No differences were found in S/F ratios between users and non-users, suggesting similar dopaminergic mechanisms underlying psychotic symptoms in both groups.

Methods of the pharmacological imaging of the cannabinoid system (PhICS) study: towards understanding the role of the brain endocannabinoid system in human cognition

Various lines of (pre)clinical research indicate that cannabinoid agents carry the potential for therapeutic application to reduce symptoms in several psychiatric disorders. However, direct testing of the involvement of cannabinoid brain systems in psychiatric syndromes is essential for further development. In the Pharmacological Imaging of the Cannabinoid System (PhICS) study, the involvement of the endocannabinoid system in cognitive brain function is assessed by comparing acute effects of the cannabinoid agonist Δ9-tetrahydrocannabinol (THC) on brain function between healthy controls and groups of psychiatric patients showing cognitive dysfunction. This article describes the objectives and methods of the PhICS study and presents preliminary results of the administration procedure on subjective and neurophysiological parameters. Core elements in the methodology of PhICS are the administration method (THC is administered by inhalation using a vaporizing device) and a comprehensive use of pharmacological magnetic resonance imaging (phMRI) combining several types of MRI scans including functional MRI (fMRI), Arterial Spin Labeling (ASL) to measure brain perfusion, and resting-state fMRI. Additional methods like neuropsychological testing further specify the exact role of the endocannabinoid system in regulating cognition. Preliminary results presented in this paper indicate robust behavioral and subjective effects of THC. In addition, fMRI paradigms demonstrate activation of expected networks of brain regions in the cognitive domains of interest. The presented administration and assessment protocol provides a basis for further research on the involvement of the endocannabionoid systems in behavior and in psychopathology, which in turn may lead to development of therapeutic opportunities of cannabinoid ligands.

Synthetic delta-9-tetrahydrocannabinol elicits schizophrenia-like negative symptoms which are distinct from sedation

OBJECTIVE

It is unknown if cannabis recreates the negative symptoms of schizophrenia.

METHODS

Healthy male volunteers (n = 22) completed two experimental sessions in which they received intravenous (IV) delta-9-tetrahydrocannabinol (THC) 2.5 mg or placebo in a randomised counterbalanced order. Negative symptoms were rated using the self-reported community assessment of psychic experiences scale (CAPE). Sedation was rated using the mood-adjective check-list (UMACL). Plasma concentrations of THC were measured over the course of the study. Data were analysed by non-parametric tests.

RESULTS

Participants reported an increase in negative symptoms from baseline under THC but not placebo conditions (p < 0.001). Negative symptoms showed no relationship with self-rated sedation or plasma concentrations of THC.

CONCLUSIONS

At plasma concentrations resembling recreational use, THC elicited schizophrenia-like negative symptoms which were not merely attributable to sedation. In the community, negative symptoms may be an adverse effect of cannabis use.

Prevalence of Substance Use in People With First-Episode Psychosis

OBJECTIVE

People experiencing a first episode of psychosis often have co-occurring substance use, which increases risk of prolonged psychosis and impairs recovery. This article examines the prevalence of substance use in people with first-episode psychosis.

METHODS

The authors searched MEDLINE and other databases for articles published between 1990 and 2009 that described current or lifetime prevalence of substance use, misuse, abuse, or dependence in individuals with first-episode psychosis.

RESULTS

Forty-four unique studies provided information. More than 25% of individuals with first-episode psychosis in reviewed studies indicated current or lifetime alcohol use, lifetime alcohol abuse/dependence, current or lifetime cannabis use, or lifetime cannabis abuse or dependence. For all substances, lifetime prevalence of abuse/dependence was higher than current abuse/dependence.

CONCLUSIONS

Despite variation in assessment methods, findings were generally consistent. Individuals with first-episode psychosis have lower current substance prevalence than lifetime prevalence, suggesting cessation of some substance use prior to seeking treatment for psychosis.

Cannabis use and progressive cortical thickness loss in areas rich in CB1 receptors during the first five years of schizophrenia

Cerebral grey matter volume reductions are progressive in schizophrenia, with larger grey matter volume decreases associated with cannabis use. It is unknown whether this grey matter loss is globally distributed over the entire brain or more pronounced in specific cortical brain regions. Fifty-one patients with recent-onset schizophrenia and 31 matched healthy subjects were included. For all subjects, magnetic resonance imaging scans were obtained at inclusion and at 5-year follow-up. Nineteen patients (ab-)used cannabis but no other illicit drugs; 32 patients and the healthy comparison subjects did not use any drugs during the 5-year follow-up. At follow-up, clinical outcome was measured. To evaluate the local differences in cortical thickness change over five years between the two groups regression analysis was carried out over the cortical surface. At inclusion cortical thickness did not differ between patients and controls and between cannabis-using and non-using patients. Over the follow-up period we found excessive thinning of the right supplementary motor cortex, inferior frontal cortex, superior temporal gyrus, angular gyrus, occipital and parietal lobe in patients relative to controls after controlling for cannabis use. Patients who used cannabis showed additional thinning in the left dorsolateral prefrontal cortex (DLPFC), left anterior cingulate cortex (ACC) and left occipital lobe as compared to those patients that did not use cannabis during the scan interval. First-episode schizophrenia patients who use cannabis show a more pronounced cortical thinning than non-using patients in areas known for their high density of CB1 receptors, such as the ACC and the DLPFC.

Rate of cannabis use disorders in clinical samples of patients with schizophrenia: a meta-analysis

OBJECTIVE

Our aim was to review recent studies and estimate the rate of cannabis use disorders (CUDs) in schizophrenia, as well as to examine the factors affecting this rate.

METHODS

We conducted an electronic search of 3 literature databases and a manual search of articles from 1996 to 2008. The key words used were "schizophreni*," "psychos*s," "psychotic," "cannabis abuse," "cannabis dependence," "cannabis use disorder," "substance use disorder," "substance abuse," "substance dependence," and "dual diagnosis." Articles that reported diagnoses according to the Diagnostic and Statistical Manual of Mental Disorders or International Classification of Diseases were included. Regression analysis was used to examine how estimated rates of CUDs are affected by various study characteristics such as the classification system, inpatient vs outpatient status, study location, proportion of males, age of the sample, or duration of illness.

RESULTS

Thirty-five studies met our search criteria. The median current rate of CUDs was 16.0% (interquartile range [IQR] = 8.6-28.6, 10 studies), and the median lifetime rate was 27.1% (IQR = 12.2-38.5, 28 studies). The median rate of CUDs was markedly higher in first-episode vs long-term patients (current 28.6%/22.0%, lifetime 44.4%/12.2%, respectively) and in studies where more than two-thirds of the participants were males than in the other studies (33.8%/13.2%). CUDs were also more common in younger samples than in the others (current 38.5%/16.0%, lifetime 45.0%/17.9%).

CONCLUSIONS

Approximately every fourth schizophrenia patient in our sample of studies had a diagnosis of CUDs. CUDs were especially common in younger and first-episode patient samples as well as in samples with a high proportion of males.

Diffusion tensor imaging in the early phase of schizophrenia: what have we learned?

The dysconnectivity model suggests that disturbed integration of neural communication is central to schizophrenia. The integrity of macro-structural brain circuits can be examined with diffusion tensor imaging (DTI), an MRI application sensitive to microstructural abnormalities of brain white matter. DTI studies in first-episode schizophrenia patients and individuals at high-risk of psychosis can provide insight into the role of structural dysconnectivity in the liability, onset and early course of psychosis. This review discusses (i) views on the role of white matter abnormalities in schizophrenia, (ii) DTI and its application in schizophrenia, (iii) DTI findings in first-episode patients and subjects at high-risk of psychosis; their timing, anatomical location and early course, (iv) the hypothesized underlying pathological substrate and possible causes of DTI white matter alterations, including effects of adolescent cannabis use, and (v) some methodological issues and future recommendations. In summary, there is evidence that DTI abnormalities convey a liability for psychosis and additional abnormalities occur around onset of psychosis. However, findings in first-episode patients are less robust than in chronic patients, and progression of disturbances may occur in the early course of poor-outcome patients. In addition, acceleration of the normal aging process may occur. Adolescent cannabis use has specific effects on DTI measures. An unresolved issue is the underlying pathology of DTI abnormalities, and combining DTI with other MRI indices can provide more insight. More research is needed on which genetic and environmental factors play a role in the variability of current results.

Cannabis use in patients with a first psychotic episode and subjects at ultra high risk of psychosis: impact on psychotic- and pre-psychotic symptoms

OBJECTIVES

Co-morbidity with cannabis use disorder is common in patients with a psychotic disorder and is associated with adverse outcome. This study aimed to determine prevalence of cannabis use disorder among patients with a psychotic disorder and subjects at ultra high risk of psychosis and to study the influence of cannabis use on severity of (pre-)psychotic symptomatology, psychosocial functioning and variables related to the course of the disorder in these patients.

METHODS

In this study 169 consecutively assessed patients with a psychotic disorder were included as well as 59 consecutively assessed subjects at ultra high risk of psychosis.

RESULTS

45% of the patients with a psychotic disorder and 27% of the UHR patients were diagnosed with a co-morbid cannabis use disorder. Patients with cannabis use disorders did not differ from patients without cannabis use disorder in severity of psychotic symptoms. However, excluding patients with substance use disorder other than cannabis use disorder resulted in higher scores on positive symptom levels for patients with cannabis use disorder compared to patients without any substance use disorder. Regarding ultra high risk patients, subjects with cannabis use disorder did not differ from subjects without cannabis use disorder on severity of pre-psychotic symptomatology. However, a negative correlation was found between the amount of cannabis used recently and scores on the pre-psychotic negative subscale.

CONCLUSION

Our results suggest a specific association between cannabis abuse and psychotic symptomatology.

Cannabinoids for the treatment of schizophrenia? A balanced neurochemical framework for both adverse and therapeutic effects of cannabis use

Recent studies have found that cannabinoids may improve neuropsychological performance, ameliorate negative symptoms, and have antipsychotic properties for a subgroup of the schizophrenia population. These findings are in contrast to the longstanding history of adverse consequences of cannabis use, predominantly on the positive symptoms, and a balanced neurochemical basis for these opposing views is lacking. This paper details a review of the neurobiological substrates of schizophrenia and the neurochemical effects of cannabis use in the normal population, in both cortical (in particular prefrontal) and subcortical brain regions. The aim of this paper is to provide a holistic neurochemical framework in which to understand how cannabinoids may impair, or indeed, serve to ameliorate the positive and negative symptoms as well as cognitive impairment. Directions in which future research can proceed to resolve the discrepancies are briefly discussed.

Cannabis use disorders in schizophrenia: effects on cognition and symptoms

OBJECTIVE

Despite the controversy surrounding the possible causal link between cannabis use and the onset of schizophrenia (SZ), data seeking to elucidate the effect of cannabis use disorders (CUDs) on the clinical presentation of SZ have produced mixed results. Although several studies have suggested that CUD in patients with SZ may be associated with variation in cognitive function, clinical presentation and course of illness, the effects have been inconsistent.

METHODS

We retrospectively ascertained a large cohort (N=455) of SZ patients with either no history of a CUD (CUD-; N=280) or a history of CUD (CUD+; N=175). The groups were initially compared on key demographic variables including sex, race, age, age at onset of SZ, parental socioeconomic status, premorbid IQ, education level and global assessment of functioning. Covarying for any observed differences in demographic variables, we then compared groups on lifetime measures of psychotic symptoms as well as a brief battery of neurocognitive tests.

RESULTS

Compared to the CUD- group the CUD+ group demonstrated significantly better performance on measures of processing speed (Trail Making Tests A and B), verbal fluency (animal naming) and verbal learning and memory (California Verbal Learning Test). Moreover, the CUD+ group had better GAF scores than the CUD group.

CONCLUSIONS

Collectively, these findings suggest that SZ patients with comorbid CUD may represent a higher functioning subgroup of SZ. Future prospective studies are needed to elucidate the nature of this relationship.

Psychosis reactivity to cannabis use in daily life: an experience sampling study

BACKGROUND

Little is known about the experiential dynamics of the interaction between cannabis and vulnerability to psychosis.

AIMS

To examine the effects of cannabis on psychotic symptoms and mood in patients with psychosis and healthy controls.

METHOD

Patients with a psychotic disorder (n = 42) and healthy controls (n = 38) were followed in their daily lives using a structured time-sampling technique.

RESULTS

Daily life cannabis use predicted subsequent increases in positive affect and in patients, but not in controls, decreases in negative affect. In patients, but not in controls, cannabis use predicted increased levels of hallucinatory experiences. Mood-enhancing properties of cannabis were acute, whereas psychosis-inducing effects were sub-acute. There was no direct evidence for self-medication effects in daily life.

CONCLUSIONS

Patients with psychosis are more sensitive to both the psychosis-inducing and mood-enhancing effects of cannabis. The temporal dissociation between acute rewarding effects and sub-acute toxic influences may be instrumental in explaining the vicious circle of deleterious use in these patients.

Illicit substance use and its correlates in first episode psychosis

OBJECTIVE

To determine if substance use (particularly cannabis) is more frequent among first episode psychosis patients and associated with a more problematic clinical presentation.

METHOD

All first episode psychosis (FEP) patients presenting to secondary services were recruited from London and Nottingham, over 2 years, in the Aetiology and Ethnicity of Schizophrenia and Other Psychoses study broad framework. Clinical and sociodemographic variables were assessed using a set of standardized instruments. A schedule was created to retrospectively collate substance use data from patients, relatives and clinicians.

RESULTS

Five hundred and eleven FEP were identified. They used three to five times more substances than general population. Substance use was associated with poorer social adjustment and a more acute mode of onset. Cannabis use did not affect social adjustment, but was associated with a more acute mode of onset.

CONCLUSION

Cannabis has a different impact on FEP than other substances. Large epidemiological studies are needed to disentangle cannabis effect.

Significance of morphological features in schizophrenia of a Chinese population

Neuro-developmental hypothesis suggests that schizophrenia is originated from aberrant brain development during first and/or early trimester of gestation. Accordingly, when a schizophrenia gene is involved in the regulation of embryonic development and continues to play a role in the later life, it may result in the co-occurrence of defective organ systems and/or physiological functions with schizophrenia. We proposed a checklist with 13 morphological features and examine their prevalence rates in 151 schizophrenic patients and 151 controls. Statistical analyses showed that single transverse palmar crease, head circumference, covered epicanthus, finger length difference, and inner canthus distance, made significant contributions to schizophrenia. To rule out the age confounding effects on morphological features, we dropped older schizophrenic subjects and younger controls in further regression analysis. The regression model correctly classified 82.8% of control subjects (specificity) and 86.4% of schizophrenic patients (sensitivity), and provided an overall successful classification rate of 84.5%, with single transverse palmar crease on the first rank. The association of morphological features and schizophrenia is probably genetic in origin, as specific morphological features were more frequent in non-affected parents with higher genetic loading of schizophrenia. In addition, the association of finger length difference in schizophrenia found in this study has never been reported elsewhere. Our study showed that five out of 13 morphological features in the propose checklist may be used as biomarkers for schizophrenia, either for clinical practice or research purposes.

Association of pre-onset cannabis, alcohol, and tobacco use with age at onset of prodrome and age at onset of psychosis in first-episode patients

OBJECTIVE

Several reports suggest that cannabis use is associated with an earlier age at onset of psychosis, although not all studies have operationalized cannabis use as occurring prior to onset of symptoms. This study addressed whether pre-onset cannabis use, alcohol use, and tobacco use are associated with an earlier age at onset of prodromal and psychotic symptoms. Effects of the progression of frequency of use were examined through time-dependent covariates in survival analyses.

METHOD

First-episode patients (N=109) hospitalized in three public-sector inpatient psychiatric units underwent in-depth cross-sectional retrospective assessments. Prior substance use and ages at onset of prodromal and psychotic symptoms were determined by standardized methods, and analyses were conducted using Cox regression modeling.

RESULTS

Whereas classifying participants according to maximum frequency of use prior to onset (none, ever, weekly, or daily) revealed no significant effects of cannabis or tobacco use on risk of onset, analysis of change in frequency of use prior to onset indicated that progression to daily cannabis and tobacco use was associated with an increased risk of onset of psychotic symptoms. Similar or even stronger effects were observed when onset of illness or prodromal symptoms was the outcome. A gender-by-daily-cannabis-use interaction was observed; progression to daily use resulted in a much larger increased relative risk of onset of psychosis in females than in males.

CONCLUSIONS

Pre-onset cannabis use may hasten the onset of psychotic as well as prodromal symptoms. Age at onset is a key prognostic factor in schizophrenia, and discovering modifiable predictors of age at onset is crucial.

Prevalence of alcohol use disorders in schizophrenia--a systematic review and meta-analysis

OBJECTIVE

Our aim was to present recent studies of alcohol use disorders (AUDs) in patients with schizophrenia, estimate overall prevalence and characteristics affecting the prevalence of AUDs.

METHOD

We conducted a search using three literature databases and a manual search on articles published in 1996-2008. Meta-regression was used to study how prevalence is affected by different study characteristics. Articles that reported diagnoses according to DSM or ICD diagnostic systems were included.

RESULTS

Altogether 60 studies met our criteria. The median of current AUD prevalence was 9.4% (inter-quartile range, IQR 4.6-19.0, 18 studies) and median of lifetime AUD prevalence 20.6% (IQR 12.0-34.5, 47 studies). In studies using DSM-III-R median prevalence was higher than that in studies using DSM-IV, ICD-9 or ICD-10 (32/17/11/6%).

CONCLUSION

Approximately every fifth patient with schizophrenia had lifetime AUD diagnosis. When contrasted with the most recent review, there might be a descending trend in AUD prevalence in patients with schizophrenia.

Cannabis using schizophrenia patients treated with atypical neuroleptics: do their symptoms differ from those of cannabis abstainers?

Several studies have found that symptom patterns of cannabis-using schizophrenia patients differ from those of nonusers. However, these investigations have mostly included patients treated with typical neuroleptics (TN). Since differing symptoms could also result from a TN-cannabis combination and might not be due to cannabis use per se, this study examined schizophrenia symptoms in a group of cannabis-using outpatients treated with atypical antipsychotics. Forty-two schizophrenia outpatients participated and were divided into three groups: cannabis abstainers, moderate users, and daily users. Patients with any substance use disorder other than cannabis abuse/dependence, or patients meeting criteria for schizotypal, schizoaffective, affective, anxiety, delusional, or personality disorders were excluded from the study. All patients completed a self-constructed questionnaire assessing demographic and drug use characteristics and were interviewed using the semistandardized Positive and Negative Syndrome Scale (PANSS). Cannabis use was assessed by self-declaration. No differences were found between the abstainers, the moderate, and the daily users on the PANSS scores. Thus, schizophrenia patients treated with atypical neuroleptics do not differ in symptom patterns whether using or not using cannabis. The study's limitations are noted.

Gene-environment interplay between cannabis and psychosis

Cannabis use is considered a contributory cause of schizophrenia and psychotic illness. However, only a small proportion of cannabis users develop psychosis. This can partly be explained by the amount and duration of the consumption of cannabis and by its strength but also by the age at which individuals are first exposed to cannabis. Genetic factors, in particular, are likely to play a role in the short- and the long-term effects cannabis may have on psychosis outcome. This review will therefore consider the interplay between genes and exposure to cannabis in the development of psychotic symptoms and schizophrenia. Studies using genetic, epidemiological, experimental, and observational techniques will be discussed to investigate gene-environment correlation gene-environment interaction, and higher order interactions within the cannabis-psychosis association. Evidence suggests that mechanisms of gene-environment interaction are likely to underlie the association between cannabis and psychosis. In this respect, multiple variations within multiple genes--rather than single genetic polymorphisms--together with other environmental factors (eg, stress) may interact with cannabis to increase the risk of psychosis. Further research on these higher order interactions is needed to better understand the biological pathway by which cannabis use, in some individuals, may cause psychosis in the short- and long term.

A comparison of symptoms and family history in schizophrenia with and without prior cannabis use: implications for the concept of cannabis psychosis

BACKGROUND

There is considerable interest in cannabis use in psychosis. It has been suggested that the chronic psychosis associated with cannabis use, is symptomatically distinct from idiopathic schizophrenia. Several studies have reported differences in psychopathology and family history in people with schizophrenia according to whether or not they were cannabis users. We set out to test the hypotheses arising from these studies that cannabis use is associated with more bizarre behaviour, more thought disorder, fewer negative symptoms including blunted affect, more delusions of reference, more paranoid delusions and a stronger family history of schizophrenia.

METHOD

We used a case register that contained 757 cases of first onset schizophrenia, 182 (24%) of whom had used cannabis in the year prior to first presentation, 552 (73%) had not and 3% had missing data. We completed the OPCRIT checklist on all patients and investigated differences in the proportion of people with distractibility, bizarre behaviour, positive formal thought disorder, delusions of reference, well organised delusions, any first rank symptom, persecutory delusions, abusive/accusatory hallucinations, blunted affect, negative thought disorder, any negative symptoms (catatonia, blunted affect, negative thought disorder, or deterioration), lack of insight, suicidal ideation and a positive family history of schizophrenia, using chi square tests. Logistic regression modelling was then used to determine whether prior cannabis use affected the presence of the characteristics after controlling for age, sex and ethnicity.

RESULTS

There was no statistically significant effect of cannabis use on the presence of any of the above. There remained however a non-significant trend towards more insight (OR 0.65 p=0.055 for "loss of insight") and a finding of fewer abusive or accusatory hallucinations (OR 0.65 p=0.049) of borderline significance amongst the cannabis users. These were in the hypothesised direction. There was no evidence of fewer negative symptoms or greater family history amongst cannabis users.

CONCLUSION

We found few appreciable differences in symptomatology between schizophrenic patients who were or were not cannabis users. There were no differences in the proportion of people with a positive family history of schizophrenia between cannabis users and non-users. This argues against a distinct schizophrenia-like psychosis caused by cannabis.

Cannabis and Psychosis: What is the Link?

Growing evidence supports the hypothesis that cannabis consumption is a risk factor for the development of psychotic symptoms. Nonetheless, controversy remains about the causal nature of the association. This review takes the debate further through a critical appraisal of the evidence. An electronic search was performed, allowing to identify 622 studies published until June 1st 2005. Longitudinal studies and literature reviews were selected if they addressed specifically the issues of the cannabis/psychosis relationship or possible mechanisms involved. Ten epidemiological studies were relevant: three supported a causal relationship between cannabis use and diagnosed psychosis; five suggested that chronic cannabis intake increases the frequency of psychotic symptoms, but not of diagnosed psychosis; and two showed no causal relationship. Potential neurobiological mechanisms were also identified, involving dopamine, endocannabinoids, and brain growth factors. Although there is evidence that cannabis use increases the risk of developing psychotic symptoms, the causal nature of this association remains unclear. Contributing factors include heavy consumption, length and early age of exposure, and psychotic vulnerability. This conclusion should be mitigated by uncertainty arising from cannabis use assessment, psychosis measurement, reverse causality and control of residual confounding.

Lifetime positive symptoms in patients with schizophrenia and cannabis abuse are partially explained by co-morbid addiction

Recent prospective findings have shown that cannabis use by young people could be a risk factor for psychotic symptoms in adulthood, but the long-term impact of cannabis abuse on the clinical features of declared schizophrenia remains to be explored. We assessed the independent influence of cannabis abuse on the clinical symptoms of schizophrenia, after controlling for frequently co-occurring addictive disorders. Patients with schizophrenia, and with (N=66), or without (N=139) cannabis abuse, were compared for lifetime positive and negative symptoms, taking into account presence of any other addictive disorders. The incidence of the abuse of drugs other than cannabis was nearly five times greater amongst patients with both schizophrenia and cannabis abuse. When the analyses were limited to subjects with no other abuse, less avolution and fewer apathy symptoms were still detected in patients with schizophrenia and cannabis abuse than in those with no abuse (p=0.0001). In contrast, between-group differences for positive symptoms were abolished when multiple substance abuses were taken into account. The strong association between cannabis abuse and fewer negative symptoms in schizophrenia was thus replicated in this sample, but once co-morbid addictive disorders had been controlled no influence of cannabis abuse on hallucinations was detected. Distinguishing the effects of co-occurring addictive disorder(s) in patients with schizophrenia and cannabis dependence may thus be important when attempting to analyse the impact of cannabis abuse.

Comorbid substance-use in schizophrenia: relation to positive and negative symptoms

As substance use disorders (SUD) are common in schizophrenia patients, we tested the hypothesis that comorbid patients (SUD[+]) have more positive vs. negative symptoms than non-comorbid (SUD[-]) patients. From reports identified by literature-searching we compared Positive and Negative Syndrome Scale (PANSS) ratings in schizophrenia patients with and without SUD using meta-analytic methods. Among 9 comparisons (N=725 subjects), SUD[+] patients were more often men, and abused alcohol>cannabis>cocaine. SUD[+] patients had very significantly higher PANSS-positive, and lower PANSS-negative scores. Comorbid SUD in schizophrenia patients was associated with male sex and higher PANSS positive to lower negative scores. Cause-effect relationships remain to be clarified.