Cannabis use and subclinical positive psychotic experiences in early adolescence: findings from a Dutch survey

Internal consistency and temporal stability of the Community Assessment of Psychic Experiences (CAPE): A reliability generalization meta-analysis

Psychotic experiences (PE) are prevalent in general and clinical populations and can increase the risk for mental disorders in young people. The Community Assessment of Psychic Experiences (CAPE) is a widely used measure to assess PE in different populations and settings. However, the current knowledge on their overall reliability is limited. We examined the reliability of the CAPE-42 and later versions, testing the role of age, sex, test scores, and clinical status as moderators. A systematic search was conducted on the Scopus, Web of Science, PubMed, EBSCOhost, ProQuest, and GoogleScholar databases. Internal consistency and temporal stability indices were examined through reliability generalization meta-analysis (RGMA). Moderators were tested through meta-regression analysis. From a pool of 1,015 records, 90 independent samples were extracted from 71 studies. Four versions showed quantitative evidence for inclusion: CAPE-42, CAPE-20, CAPE-P15, and CAPE-P8. Internal consistency indices were good (α/ω≈.725-0.917). Temporal stability was only analyzed for the CAPE-P15, yielding a moderate but not-significant effect (r=0.672). The evidence for temporal stability is scant due to the limited literature, and definitive conclusions cannot be drawn. Further evidence on other potential moderators such as adverse experiences or psychosocial functioning is required.

The association between traumatic experiences and substance and behavioral addictions in late adolescence: A role for PTSD and cPTSD as potential mediators

BACKGROUND & AIM

Traumatic experiences (TEs) are a risk factor for behavioral and substance addictions (SBAs). However, the role of post-traumatic stress disorder (PTSD) and complex PTSD (cPTSD) deserves further elucidation. The present study assesses the association between different types of TEs on cannabis, alcohol, gambling, and problematic internet use in late adolescents. Furthermore, this study aims at evaluating the role of PTSD and cPTSD as potential mediators.

METHODS

An observational cross-sectional study was conducted on one thousand ten late adolescents (510 males, 498 females; age: mean = 18.7, SD = 0.65). Data regarding intentional (iTEs) and unintentional TEs (uTEs), cannabis, alcohol, gambling and problematic use of the internet (PIU), PTSD, and cPTSD were collected. Association between TEs, SBAs, and PTSD/cPTSD symptoms were explored by means of logistic regressions. Mediation was assessed using a path analysis.

RESULTS

uTEs were associated with cannabis use (OR = 1.34 [1.13,1.59]) and alcohol use (OR = 1.21 [1.10,1.35]), iTEs were associated with cannabis use (OR = 1.15 [1.06,1.25]), alcohol use (OR = 1.08 [1.02,1.13]), and PIU (OR = 1.17 [1.10,1.24]). PTSD was associated with alcohol use (OR = 1.59 [1.03,2.46]) and PIU (OR = 1.92 [1.18,3.13]). cPTSD was associated with cannabis use (OR = 3.54 [1.56,8.04]) and PIU (OR = 5.13 [2.71,9.70]). cPTSD mediated 58.75% of the total effect of iTEs on cannabis. Regarding PIU, PTSD mediated 68.18% of the effect of uTEs; the effect of iTEs on PIU was mediated by 65.5% via cPTSD and 34.45% via PTSD.

CONCLUSION

cPTSD and SBAs show a complex pattern of association. A thorough assessment of stress-related conditions, including cPTSD, is of pivotal importance in treating SBAs.

Independent contribution of polygenic risk for schizophrenia and cannabis use in predicting psychotic-like experiences in young adulthood: testing gene × environment moderation and mediation

BACKGROUND

It has not yet been determined if the commonly reported cannabis-psychosis association is limited to individuals with pre-existing genetic risk for psychotic disorders.

METHODS

We examined whether the relationship between polygenic risk score for schizophrenia (PRS-Sz) and psychotic-like experiences (PLEs), as measured by the Community Assessment of Psychic Experiences-42 (CAPE-42) questionnaire, is mediated or moderated by lifetime cannabis use at 16 years of age in 1740 of the individuals of the European IMAGEN cohort. Secondary analysis examined the relationships between lifetime cannabis use, PRS-Sz and the various sub-scales of the CAPE-42. Sensitivity analyses including covariates, including a PRS for cannabis use, were conducted and results were replicated using data from 1223 individuals in the Dutch Utrecht cannabis cohort.

RESULTS

PRS-Sz significantly predicted cannabis use (p = 0.027) and PLE (p = 0.004) in the IMAGEN cohort. In the full model, considering PRS-Sz and covariates, cannabis use was also significantly associated with PLE in IMAGEN (p = 0.007). Results remained consistent in the Utrecht cohort and through sensitivity analyses. Nevertheless, there was no evidence of a mediation or moderation effects.

CONCLUSIONS

These results suggest that cannabis use remains a risk factor for PLEs, over and above genetic vulnerability for schizophrenia. This research does not support the notion that the cannabis-psychosis link is limited to individuals who are genetically predisposed to psychosis and suggests a need for research focusing on cannabis-related processes in psychosis that cannot be explained by genetic vulnerability.

Substance use and psychotic-like experiences in young people: a systematic review and meta-analysis

This study aimed to systematically review and synthesise the available evidence on the prevalence and associations between psychotic-like experiences (PLEs) and substance use in children and adolescents aged ⩽17 years, prior to the typical age of development of prodromal symptoms of psychosis. As substance use has been associated with earlier age of psychosis onset and more severe illness, identifying risk processes in the premorbid phase of the illness may offer opportunities to prevent the development of prodromal symptoms and psychotic illness. MEDLINE, PsycINFO, and CINAHL databases were searched for chart review, case-control, cohort, twin, and cross-sectional studies. Study reporting was assessed using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist, and pooled evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Searches identified 55 studies that met inclusion criteria. Around two-in-five substance users reported PLEs [rate = 0.41, 95% confidence interval (CI) 0.32-0.51; low quality evidence], and one-in-five with PLEs reported using substances (rate = 0.19, 95% CI 0.12-0.28; moderate-to-high quality evidence). Substance users were nearly twice as likely to report PLEs than non-users [odds ratio (OR) 1.77, 95% CI 1.55-2.02; moderate quality evidence], and those with PLEs were twice as likely to use substances than those not reporting PLEs (OR 1.93, 95% CI 1.55-2.41; very low quality evidence). Younger age was associated with greater odds of PLEs in substance users compared to non-users. Young substance users may represent a subclinical at-risk group for psychosis. Developing early detection and intervention for both substance use and PLEs may reduce long-term adverse outcomes.

Association between age of cannabis initiation and gray matter covariance networks in recent onset psychosis

Cannabis use during adolescence is associated with an increased risk of developing psychosis. According to a current hypothesis, this results from detrimental effects of early cannabis use on brain maturation during this vulnerable period. However, studies investigating the interaction between early cannabis use and brain structural alterations hitherto reported inconclusive findings. We investigated effects of age of cannabis initiation on psychosis using data from the multicentric Personalized Prognostic Tools for Early Psychosis Management (PRONIA) and the Cannabis Induced Psychosis (CIP) studies, yielding a total sample of 102 clinically-relevant cannabis users with recent onset psychosis. GM covariance underlies shared maturational processes. Therefore, we performed source-based morphometry analysis with spatial constraints on structural brain networks showing significant alterations in schizophrenia in a previous multisite study, thus testing associations of these networks with the age of cannabis initiation and with confounding factors. Earlier cannabis initiation was associated with more severe positive symptoms in our cohort. Greater gray matter volume (GMV) in the previously identified cerebellar schizophrenia-related network had a significant association with early cannabis use, independent of several possibly confounding factors. Moreover, GMV in the cerebellar network was associated with lower volume in another network previously associated with schizophrenia, comprising the insula, superior temporal, and inferior frontal gyrus. These findings are in line with previous investigations in healthy cannabis users, and suggest that early initiation of cannabis perturbs the developmental trajectory of certain structural brain networks in a manner imparting risk for psychosis later in life.

Are psychotic-like experiences related to a discontinuation of cannabis consumption in young adults?

OBJECTIVE

To assess changes in cannabis use in young adults as a function of psychotic-like experiences.

METHOD

Participants were initially recruited at age 14 in high schools for the longitudinal IMAGEN study. All measures presented here were assessed at follow-ups at age 19 and at age 22, respectively. Perceived stress was only assessed once at age 22. Ever users of cannabis (N = 552) gave qualitative and quantitative information on cannabis use and psychotic-like experiences using the Community Assessment of Psychic Experiences (CAPE). Of those, nearly all n = 549 reported to have experienced at least one psychotic experience of any form at age 19.

RESULTS

Mean cannabis use increased from age 19 to 22 and age of first use of cannabis was positively associated with a change in cannabis use between the two time points. Change in cannabis use was not significantly associated with psychotic-like experiences at age 19 or 22. In exploratory analysis, we observed a positive association between perceived stress and the experience of psychotic experiences at age 22.

CONCLUSION

Age of first use of cannabis influenced trajectories of young cannabis users with later onset leading to higher increase, whereas the frequency of psychotic-like experiences was not associated with a change in cannabis use. The observed association between perceived stress and psychotic-like experiences at age 22 emphasizes the importance of stress experiences in developing psychosis independent of cannabis use.

Educational Response to a Student with Psychosis at the Secondary Level: A Non-Experimental Single-Case Study

Students with psychosis in school within the ordinary education system are a reality in the classroom. To study their correct adaptation at school, it is necessary to consider numerous factors such as the personal characteristics of the student, environmental variables, educational measures put in place as well as emotional and cognitive aspects. The aim of this research was to monitor the teaching-learning process of a student diagnosed with psychosis and enrolled in a public school at the secondary level in the ordinary modality with support during an academic year, with the usual resources provided by a guidance department to assess the impact of the educational measures and plans on his emotional and academic fields. This was a single case study in which both qualitative and quantitative information was collected (N = 1). The participant was a student with special needs at the secondary level. An analysis of the results of psychometric tests, plan for diversity, observational analysis, academic file, scholastic history, and multiple interviews were carried out. The findings show how the educational curriculum can be adapted to improve the competences of a student with psychosis by encouraging an increase in social abilities and potential cognitive abilities through the counseling department. The conclusions of this research can provide a guideline for comparison of different educational systems, paying greater attention to the development of emotional aspects, and opting for inclusive measures. In this line, this study shows that students with psychosis can share classrooms and studies with their peers, thus fulfilling the principle of educational inclusion.

Does cannabis use predict psychometric schizotypy via aberrant salience?

Cannabis can induce acute psychotic symptoms in healthy individuals and exacerbate pre-existing psychotic symptoms in patients with schizophrenia. Inappropriate salience allocation is hypothesised to be central to the association between dopamine dysregulation and psychotic symptoms. This study examined whether cannabis use is associated with self-reported salience dysfunction and schizotypal symptoms in a non-clinical population. 910 University students completed the following questionnaire battery: the cannabis experience questionnaire modified version (CEQmv); schizotypal personality questionnaire (SPQ); community assessment of psychic experience (CAPE); aberrant salience inventory (ASI). Mediation analysis was used to test whether aberrant salience mediated the relationship between cannabis use and schizotypal traits. Both frequent cannabis consumption during the previous year and ASI score predicted variation across selected positive and disorganised SPQ subscales. However, for the SPQ subscales 'ideas of reference' and 'odd beliefs', mediation analysis revealed that with the addition of ASI score as a mediating variable, current cannabis use no longer predicted scores on these subscales. Similarly, cannabis use frequency predicted higher total SPQ as well as specific Positive and Disorganised subscale scores, but ASI score as a mediating variable removed the significant predictive relationship between frequent cannabis use and 'odd beliefs', 'ideas of reference', 'unusual perceptual experiences', 'odd speech', and total SPQ scores. In summary, cannabis use was associated with increased psychometric schizotypy and aberrant salience. Using self-report measures in a non-clinical population, the cannabis-related increase in selected positive and disorganised SPQ subscale scores was shown to be, at least in part, mediated by disturbance in salience processing mechanisms.

Cannabis-Associated Psychotic-like Experiences Are Mediated by Developmental Changes in the Parahippocampal Gyrus

OBJECTIVE

Cannabis consumption during adolescence has been reported as a risk factor for psychotic-like experiences (PLEs) and schizophrenia. However, brain developmental processes associated with cannabis-related PLEs are still poorly described.

METHOD

A total of 706 adolescents from the general population who were recruited by the IMAGEN consortium had structural magnetic resonance imaging scans at both 14 and 19 years of age. We used deformation-based morphometry to map voxelwise brain changes between the two time points, using the pairwise algorithm in SPM12b. We used an a priori region-of-interest approach focusing on the hippocampus/parahippocampus to perform voxelwise linear regressions. Lifetime cannabis consumption was assessed using the European School Survey Project on Alcohol and other Drugs (ESPAD), and PLEs were assessed with the Comprehensive Assessment Psychotic-like experiences (CAPE) tool. We first tested whether hippocampus/parahippocampus development was associated with PLEs. Then we formulated and tested an a priori simple mediation model in which uncus development mediates the association between lifetime cannabis consumption and PLEs.

RESULTS

We found that PLEs were associated with reduced expansion within a specific region of the right hippocampus/parahippocampus formation, the uncus (p = .002 at the cluster level, p = .018 at the peak level). The partial simple mediation model revealed a significant total effect from lifetime cannabis consumption to PLEs (b = 0.069, 95% CI = 0.04-0.1, p =2 × 10^-16), as well as a small yet significant, indirect effect of right uncus development (0.004; 95% CI = 0.0004-0.01, p = .026).

CONCLUSION

We show here that the uncus development is involved in the cerebral basis of PLEs in a population-based sample of healthy adolescents.

Terminology and assessment tools of psychosis: A systematic narrative review

AIM

Phenomena within the psychosis continuum that varies in frequency/duration/intensity have been increasingly identified. Different terms describe these phenomena, however there is no standardization within the terminology. This review evaluated the definitions and assessment tools of seven terms - (i) 'psychotic experiences'; (ii) 'psychotic-like experiences'; (iii) 'psychotic-like symptoms'; (iv) 'attenuated psychotic symptoms'; (v) 'prodromal psychotic symptoms'; (vi) 'psychotic symptomatology'; and (vii) 'psychotic symptoms'.

METHODS

EMBASE, MEDLINE, and CINAHL were searched during February-March 2019. Inclusion criteria included 1989-2019, full text, human, and English. Papers with no explicit definition or assessment tool, duplicates, conference abstracts, systematic reviews, meta-analyses, or no access were excluded.

RESULTS

A total of 2238 papers were identified and of these, 627 were included. Definitions and assessment tools varied, but some trends were found. Psychotic experiences and psychotic-like experiences were transient and mild, found in the general population and those at-risk. Psychotic-like symptoms were subthreshold and among at-risk populations and non-psychotic mental disorders. Attenuated psychotic symptoms were subthreshold but associated with distress, risk, and help-seeking. Prodromal psychotic symptoms referred to the prodrome of psychotic disorders. Psychotic symptomatology included delusions and hallucinations within psychotic disorders. Psychotic symptoms was the broadest term, encompassing a range of populations but most commonly involving hallucinations, delusions, thought disorder, and disorganization.

DISCUSSION

A model for conceptualizing the required terms is proposed and future directions needed to advance this field of research are discussed.

The interplay between childhood trauma, cognitive biases, and cannabis use on the risk of psychosis in nonclinical young adults in Poland

Background.

Childhood traumatic events are risk factors for psychotic-like experiences (PLEs). However, the mechanisms explaining how trauma may contribute to the development of PLEs are not fully understood. In our study, we investigated whether cannabis use and cognitive biases mediate the relationship between early trauma and PLEs.

Methods.

A total sample of 6,772 young adults (age 26.6 ± 4.7, 2,181 male and 3,433 female) was recruited from the general population to participate in an online survey. We excluded 1,158 individuals due to a self-reported lifetime diagnosis of any mental disorder. The online survey included selected items from the following questionnaires: Traumatic Experience Checklist (TEC, 3 items), Childhood Experience of Care and Abuse Questionnaire (CECA.Q, 3 items), Cannabis Problems Questionnaire (CPQ, 10 items), Davos Assessment of Cognitive Biases Scale (DACOBS-18, 9 items), and Prodromal Questionnaire-16 (PQ-16). Mediation analyses were performed with respect to different categories of traumatic experiences (emotional, physical and sexual abuse as well as emotional neglect).

Results.

Our results showed significant associations of any time of childhood trauma with higher scores of cannabis use (CPQ), cognitive biases (DACOBS), and PLEs (PQ-16) (p < 0.001). We found a direct effect of childhood trauma on PLEs as well as significant indirect effect mediated through cannabis use and cognitive biases. All models tested for the effects of specific childhood adversities revealed similar results. The percentage of variance in PQ-16 scores explained by serial mediation models varied between 32.8 and 34.2% depending on childhood trauma category.

Conclusion.

Cannabis use and cognitive biases play an important mediating role in the relationship between childhood traumatic events and the development of PLEs in a nonclinical young adult population.

Factors Moderating the Association Between Cannabis Use and Psychosis Risk: A Systematic Review

Increasing evidence indicates a relationship between cannabis use and psychosis risk. Specific factors, such as determinants of cannabis use or the genetic profile of cannabis users, appear to moderate this association. The present systematic review presents a detailed and up-to-date literature overview on factors that influence the relationship between cannabis use and psychosis risk. A systematic search was performed according to the PRISMA guidelines in MEDLINE and Embase, and 56 studies were included. The results show that, in particular, frequent cannabis use, especially daily use, and the consumption of high-potency cannabis are associated with a higher risk of developing psychosis. Moreover, several genotypes moderate the impact of cannabis use on psychosis risk, particularly those involved in the dopamine function, such as AKT1. Finally, cannabis use is associated with an earlier psychosis onset and increased risk of transition in individuals at a clinical high risk of psychosis. These findings indicate that changing cannabis use behavior could be a harm reduction strategy employed to lower the risk of developing psychosis. Future research should aim to further develop specific biomarkers and genetic profiles for psychosis, thereby contributing to the identification of individuals at the highest risk of developing a psychotic disorder.

Delta-9-tetrahydrocannabinol increases striatal glutamate levels in healthy individuals: implications for psychosis

The neurobiological mechanisms underlying the association between cannabis use and acute or long-lasting psychosis are not completely understood. While some evidence suggests altered striatal dopamine may underlie the association, direct evidence that cannabis use affects either acute or chronic striatal dopamine is inconclusive. In contrast, pre-clinical research suggests that cannabis may affect dopamine via modulation of glutamate signaling. A double-blind, randomized, placebo-controlled, crossover design was used to investigate whether altered striatal glutamate, as measured using proton magnetic resonance spectroscopy, underlies the acute psychotomimetic effects of intravenously administered delta-9-tetrahydrocannabinol (Δ9-THC; 1.19 mg/2 ml), the key psychoactive ingredient in cannabis, in a set of 16 healthy participants (7 males) with modest previous cannabis exposure. Compared to placebo, acute administration of Δ9-THC significantly increased Glutamate (Glu) + Glutamine (Gln) metabolites (Glx) in the left caudate head (P = 0.027). Furthermore, compared to individuals who were not sensitive to the psychotomimetic effects of Δ9-THC, individuals who developed transient psychotic-like symptoms (~70% of the sample) had significantly lower baseline Glx (placebo; P 7= 0.023) and a 2.27-times higher increase following Δ9-THC administration. Lower baseline Glx values (r = -0.55; P = 0.026) and higher previous cannabis exposure (r = 0.52; P = 0.040) were associated with a higher Δ9-THC-induced Glx increase. These results suggest that an increase in striatal glutamate levels may underlie acute cannabis-induced psychosis while lower baseline levels may be a marker of greater sensitivity to its acute psychotomimetic effects and may have important public health implications.

A Twin Study on the Association Between Psychotic Experiences and Tobacco Use During Adolescence

OBJECTIVE

Psychotic experiences (PE) are dimensional phenomena in the general population that resemble psychotic symptoms, such as paranoia and hallucinations. This is the first twin study to explore the degree to which tobacco use and PE share genetic or environmental influences. Previous studies on the association between adolescent tobacco use and PE have not considered PE dimensionally, included negative symptoms, or accounted for confounding by sleep disturbance and stressful life events.

METHOD

An unselected adolescent twin sample (N = 3,787 pairs; mean age = 16.16 years) reported on PE (paranoia, hallucinations, cognitive disorganization, grandiosity, and anhedonia) and regularity of tobacco use. Parents rated the twins' negative symptoms. Regression analyses were conducted while adjusted for sociodemographic characteristics, prenatal maternal smoking, cannabis use, sleep disturbance, and stressful life events. Bivariate twin modeling was used to estimate the degree of genetic and common and unique environmental influences shared between tobacco use and PE.

RESULTS

Regular smokers were significantly more likely to experience paranoia, hallucinations, cognitive disorganization, and negative symptoms (β = 0.17-0.34), but not grandiosity or anhedonia, than nonsmokers, after adjustment for confounders. Paranoia, hallucinations, and cognitive disorganization correlated ≥0.15 with tobacco use (r = 0.15-0.21, all p < .001). Significant genetic correlations (r_A=0.37-0.45) were found. Genetic influences accounted for most of the association between tobacco use and paranoia (84%) and cognitive disorganization (81%). Familial influences accounted for 80% of the association between tobacco use and hallucinations.

CONCLUSION

Tobacco use and PE during adolescence were associated after adjustment for confounders. They appear to co-occur largely because of shared genetic influences.

Genetic Predisposition vs Individual-Specific Processes in the Association Between Psychotic-like Experiences and Cannabis Use

Importance

Previous research indicates that cannabis use is associated with psychotic-like experiences (PLEs). However, it is unclear whether this association results from predispositional (ie, shared genetic) factors or individual-specific factors (eg, causal processes, such as cannabis use leading to PLEs).

Objectives

To estimate genetic and environmental correlations between cannabis use and PLEs, and to examine PLEs in twin and nontwin sibling pairs discordant for exposure to cannabis use to disentangle predispositional from individual-specific effects.

Design, Setting, and Participants

In this cross-sectional analysis, diagnostic interviews and self-reported data were collected from 2 separate population-based samples of twin and nontwin sibling pairs. Data from the Human Connectome Project were collected between August 10, 2012, and September 29, 2015, and data from the Australian Twin Registry Cohort 3 (ATR3) were collected between August 1, 2005, and August 31, 2010. Data were analyzed between August 17, 2017, and July 6, 2018. The study included data from 1188 Human Connectome Project participants and 3486 ATR3 participants, totaling 4674 participants.

Main Outcomes and Measures

Three cannabis-involvement variables were examined: frequent use (ie, ≥100 times), a DSM-IV lifetime cannabis use disorder diagnosis, and current cannabis use. Genetic and environmental correlations between cannabis involvement and PLEs were estimated. Generalized linear mixed models examined PLE differences in twin and nontwin sibling pairs discordant for cannabis use.

Results

Among the 4674 participants, the mean (SD) age was 30.5 (3.2) years, and 2923 (62.5%) were female. Data on race/ethnicity were not included as a covariate owing to lack of variability within the ATR3 sample; among the 1188 participants in the Human Connectome Project, 875 (73.7%) were white. Psychotic-like experiences were associated with frequent cannabis use (β = 0.11; 95% CI, 0.08-0.14), cannabis use disorder (β = 0.13; 95% CI, 0.09-0.16), and current cannabis use (β = 0.07; 95% CI, 0.04-0.10) even after adjustment for covariates. Correlated genetic factors explained between 69.2% and 84.1% of this observed association. Within discordant pairs of twins/siblings (Npairs, 308-324), Psychotic-like experiences were more common in cannabis-exposed individuals compared with their relative who used cannabis to a lesser degree (β ≥ .23, P < .05; eg, frequent and infrequent cannabis-using relatives significantly differed, z = -5.41; P < .001).

Conclusions and Relevance

Despite the strong contribution of shared genetic factors, frequent and problem cannabis use also appears to be associated with PLEs via person-specific pathways. This study's findings suggest that policy discussions surrounding legalization should consider the influence of escalations in cannabis use on traitlike indices of vulnerability, such as PLEs, which could contribute to pervasive psychological and interpersonal burden.

Cannabis use as a risk factor for psychotic-like experiences: A systematic review of non-clinical populations evaluated with the Community Assessment of Psychic Experiences

AIM

Epidemiological data have provided evidence that psychotic-like experiences (PLEs) can occur in the general population, not necessarily accompanied by the impairment and suffering observed in formal psychiatric diagnoses. According to the psychosis continuum hypothesis, PLEs would be subject to the same risk factors as frank psychosis. The aim of this review was to summarize observational studies that evaluated cannabis use as a risk factor for PLEs as determined by the Community Assessment of Psychic Experiences in non-clinical samples. The instrument composed of 3 dimensions-positive, negative and depressive-is a scale specifically designed to assess the occurrence, frequency and impact of PLEs in non-clinical population.

METHODS

We searched PubMed/Medline, Web of Science and PsycInfo electronic databases for indexed peer-reviewed studies published until September 2017.

RESULTS

We initially identified 100 articles. The PRISMA model for systematic reviews was used and 19 full-text articles were analysed. In general, the findings suggested that the higher the cannabis use and the younger the participants, the higher the reports of PLEs, although associations were more consistent for the positive dimension.

CONCLUSIONS

More attention should be paid to the understanding of the risk factors of PLEs in the general population, since these experiences are themselves a risk for psychotic disorders.

Longitudinal assessment of the effect of cannabis use on hospital readmission rates in early psychosis: A 6-year follow-up in an inpatient cohort

Cannabis is the most commonly used illicit drug in psychosis patients and has been identified as a risk factor for relapse and subsequent hospital readmission, having substantial economic implications. To clarify the contribution of cannabis consumption to hospital readmission, a consecutive inpatient cohort of 161 early psychosis patients was included into the study. Data on cannabis use at admission and number of hospital readmissions and length of stay (LOS, number of inpatient days) in a 6-year follow-up was extracted from clinical notes. 62.4% of the patients had lifetime cannabis use. Their admission lasted on average 54.3 ± 75 days and over the following 6 years patients had 2.2 ± 2.8 hospital readmissions, for a total of 197.4 ± 331.5 days. Cannabis use significantly predicted the number of hospital readmissions and LOS in the following 6 years, the latter remaining significant after adjusting for use of other substance. Cannabis-using patients of male gender and Black ethnicity had a longer LOS at follow-up compared to female patients and other ethnic groups, respectively. Having a history of cannabis use when admitted to an early intervention inpatient unit for psychosis is associated with a higher number of subsequent hospital readmissions and a longer LOS, especially in male and Black patients.

Genetic vulnerability to schizophrenia is associated with cannabis use patterns during adolescence

BACKGROUND

Previously reported comorbidity between schizophrenia and substance use may be explained by shared underlying risk factors, such as genetic background. The aim of the present longitudinal study was to investigate how a genetic predisposition to schizophrenia was associated with patterns of substance use (cannabis use, smoking, alcohol use) during adolescence (comparing ages 13-16 with 16-20 years).

METHOD

Using piecewise latent growth curve modelling in a longitudinal adolescent cohort (RADAR-Y study, N = 372), we analyzed the association of polygenic risk scores for schizophrenia (PRS; p-value thresholds (p_t) < 5e-8 to p_t < 0.5) with increase in substance use over the years, including stratified analyses for gender. Significance thresholds were set to adjust for multiple testing using Bonferroni at p ≤ 0.001.

RESULTS

High schizophrenia vulnerability was associated with a stronger increase in cannabis use at age 16-20 (PRS thresholds p_t < 5e-5 and p_t < 5e-4; p_t < 5e-6 was marginally significant), whereas more lenient PRS thresholds (PRS thresholds p_t < 5e-3 to p_t < 0.5) showed the reverse association. For smoking and alcohol, no clear relations were found.

CONCLUSIONS

In conclusion, our findings support a relation between genetic risk to schizophrenia and prospective cannabis use patterns during adolescence. In contrast, no relation between alcohol and smoking was established.

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.

U-shaped curve of psychosis according to cannabis use: New evidence from a snowball sample

BACKGROUND

The aim of this study was to investigate the relationship between psychotic-like experiences (PLEs) assessed using the Community Assessment of Psychic Experience (CAPE) questionnaire and the pattern of cannabis use in a non-clinical sample collected by snowball sampling.

METHODS

Our sample was composed of 204 subjects, distributed into three groups by their cannabis use pattern: 68 were non-cannabis users, 40 were moderate cannabis users and 96 were daily cannabis users. We assessed the psychotic experiences in each group with the CAPE questionnaire; and then controlled for the effect of possible confounding factors like sex, age, social exclusion, age of onset of cannabis use, alcohol use and other drug use.

RESULTS

We found a significant quadratic association between the frequency of cannabis use and positive (β = -1.8; p = 0.004) and negative dimension scores (β = -1.2; p = 0.04). The first-rank and mania factors showed a significant quadratic association (p < 0.05), while the voices factor showed a trend (p = 0.07). Scores for the different groups tended to maintain a U-shape in their values for the different factors. When we adjusted for gender, age, social exclusion, age of onset of cannabis use, and use of alcohol and other drugs, only the first-rank experiences remained significant.

CONCLUSIONS

We found there was a U-shaped curve in the association between cannabis use and the positive and negative dimensions of the CAPE score. We also found this association in mania and first-rank experiences.

Medicinal Cannabis for Parkinson's Disease: Practices, Beliefs, and Attitudes Among Providers at National Parkinson Foundation Centers of Excellence

Background

Legalization of the medical use of cannabis for Parkinson's disease (PD) has bypassed the traditional drug-approval process, leaving physicians with little evidence with which to guide patients.

Objective

The goal of this study was to gather data on the cannabis-related prescribing practices and views regarding potential risks and benefits of cannabis among experts caring for patients with PD.

Methods

An anonymous, 73-item online survey was conducted through an online service (SurveyMonkey) and included neurologists at all National Parkinson Foundation Centers of Excellence.

Results

Fifty-six responders represented centers across 5 countries and 14 states. 23% reported some formal education on cannabis. Eighty percent of responders had patients with PD who used cannabis, and 95% were asked to prescribe it. Fifty-two percent took a neutral position on cannabis use with their patients, 9% discouraged use, and 39% encouraged it. Most believed that the literature supported use of cannabis for nausea (87%; n = 48), anxiety (60%; n = 33), and pain (86%; n = 47), but responses were divided with regard to motor symptoms. Most respondents expected that cannabis would worsen motivation (59%; n = 32), sleepiness (60%; n = 31), and hallucinations (69%; n = 37). In addition, most feared negative effects on short-term memory (75%; n = 42), long-term memory (55%; n = 31), executive functioning (79%; n = 44), and driving (96%; n = 54). Although many did not believe that cannabis should be recreational (50%; n = 28), most believed that it should be legalized for medicinal purposes (69.6%; n = 39).

Conclusions

This study provides data on the cannabis-related practices, beliefs, and attitudes of expert PD physicians. There is a lack of consensus that likely reflects a general knowledge gap and paucity of data to guide clinical practice.

Cannabis Liberalization and Adolescent Cannabis Use: A Cross-National Study in 38 Countries

AIMS

To assess the associations between types of cannabis control policies at country level and prevalence of adolescent cannabis use.

SETTING, PARTICIPANTS AND DESIGN

Multilevel logistic regressions were performed on 172,894 adolescents 15 year of age who participated in the 2001/2002, 2005/2006, or 2009/2010 cross-sectional Health Behaviour in School-Aged Children (HBSC) survey in 38 European and North American countries.

MEASURES

Self-reported cannabis use status was classified into ever use in life time, use in past year, and regular use. Country-level cannabis control policies were categorized into a dichotomous measure (whether or not liberalized) as well as 4 detailed types (full prohibition, depenalization, decriminalization, and partial prohibition). Control variables included individual-level sociodemographic characteristics and country-level economic characteristics.

FINDINGS

Considerable intra-class correlations (.15-.19) were found at country level. With respect to the dichotomized cannabis control policy, adolescents were more likely to ever use cannabis (odds ratio (OR) = 1.10, p = .001), use in past year (OR = 1.09, p = .007), and use regularly (OR = 1.26, p = .004). Although boys were substantially more likely to use cannabis, the correlation between cannabis liberalization and cannabis use was smaller in boys than in girls. With respect to detailed types of policies, depenalization was associated with higher odds of past-year use (OR = 1.14, p = .013) and regular use (OR = 1.23, p = .038), and partial prohibition was associated with higher odds of regular use (OR = 2.39, p = .016). The correlation between cannabis liberalization and regular use was only significant after the policy had been introduced for more than 5 years.

CONCLUSIONS

Cannabis liberalization with depenalization and partial prohibition policies was associated with higher levels of regular cannabis use among adolescents. The correlations were heterogeneous between genders and between short- and long-terms.

Cannabinoids and Schizophrenia: Risks and Therapeutic Potential

A convergence of evidence shows that use of Cannabis sativa is associated with increased risk of developing psychotic disorders, including schizophrenia, and earlier age at which psychotic symptoms first manifest. Cannabis exposure during adolescence is most strongly associated with the onset of psychosis amongst those who are particularly vulnerable, such as those who have been exposed to child abuse and those with family histories of schizophrenia. Schizophrenia that develops after cannabis use may have a unique clinical phenotype, and several genetic polymorphisms may modulate the relationship between cannabis use and psychosis. The endocannabinoid system has been implicated in psychosis both related and unrelated to cannabis exposure, and studying this system holds potential to increase understanding of the pathophysiology of schizophrenia. Anandamide signaling in the central nervous system may be particularly important. Δ(9)-Tetrahydrocannabinol in cannabis can cause symptoms of schizophrenia when acutely administered, and cannabidiol (CBD), another compound in cannabis, can counter many of these effects. CBD may have therapeutic potential for the treatment of psychosis following cannabis use, as well as schizophrenia, possibly with better tolerability than current antipsychotic treatments. CBD may also have anti-inflammatory and neuroprotective properties. Establishing the role of CBD and other CBD-based compounds in treating psychotic disorders will require further human research.

Psychotic experiences are linked to cannabis use in adolescents in the community because of common underlying environmental risk factors

Cannabis users are more likely to have psychotic experiences (PEs). The degree to which these associations are driven by genetic or environmental influences in adolescence is unknown. This study estimated the genetic and environmental contributions to the relationship between cannabis use and PEs. Specific PEs were measured in a community-based twin sample (4830 16-year-old pairs) using self-reports and parent-reports. Adolescents reported on ever using cannabis. Multivariate liability threshold structural equation model-fitting was conducted. Cannabis use was significantly correlated with PEs. Modest heritability (37%), common environmental influences (55%) and unique environment (8%) were found for cannabis use. For PEs, modest heritability (27-54%), unique environmental influences (E=12-50%) and little common environmental influences (11-20%), with the exception of parent-rated Negative Symptoms (42%), were reported. Environmental influences explained all of the covariation between cannabis use and paranoia, cognitive disorganization and parent-rated negative symptoms (bivariate common environment=69-100%, bivariate unique environment=28-31%), whilst the relationship between cannabis use and hallucinations indicated familial influences. Cannabis use explains 2-5% of variance in positive, cognitive, and negative PEs. Cannabis use and psychotic experience co-occur due to environmental factors. Focus on specific environments may reveal why adolescent cannabis use and psychotic experiences tend to 'travel together'.

Association between cannabis use and schizotypal dimensions--a meta-analysis of cross-sectional studies

Cannabis consumption can cause abuse and dependence and increase risk of developing psychiatric and somatic disorders. Several literature reviews explored the link between cannabis consumption and schizophrenia but none summarized the rich literature on cannabis and psychometric schizotypy. The aim of our review is to synthesize data from studies that explored the association between cannabis consumption and schizoptypal dimensions. A systematic review of the literature and, when needed, contact with the authors, allowed us to gather data from 29 cross-sectional studies. We compared schizotypy scores between subjects that never used cannabis and subjects that used it at least once ("never vs. ever") and between current users and subjects that do not use cannabis currently ("current vs. other"). We conducted separate analyses for total schizotypy score and each of the three classical schizotypal dimensions (positive, negative, disorganized). For all eight comparisons, the cannabis group ("ever" or "current") had higher schizotypy scores. Differences were in the small or medium range and, with the exception of the negative score in the current vs. other comparison, statistically significant. Cannabis consumption is associated with increased schizotypal traits. More research, using different approaches (e.g. longitudinal studies) is needed to explore the cause of this association.

Anxiety mediates the association between cannabis use and attenuated positive psychotic symptoms

Cannabis use has been associated with a continuum of psychotic experiences. However, it is unclear whether mood and anxiety symptoms account for increases in attenuated positive psychotic symptoms (APPS) among cannabis users. We predicted that depression and anxiety symptoms would mediate the relation between cannabis use and APPS, and between cannabis use and endorsement of eight or more distressing APPS (D-APPS), a potentially more clinically meaningful group. Young adults (n=674) completed the Prodromal Questionnaire (PQ); Drug Use Frequency measure; Center for Epidemiologic Studies Depression Scale; State-Trait Anxiety Inventory, Trait Form, Anxiety Subscale; and Social Phobia Scale. Results indicated that symptoms of trait anxiety, but not symptoms of depression or social anxiety, mediated the relationship between cannabis use and APPS, as well as the relationship between cannabis use and D-APPS. Results indicate that symptoms of trait anxiety may play a role in the relation between cannabis use and APPS. Findings underscore the importance of considering clinical characteristics co-occurring with psychotic symptoms, such as affective symptoms, when examining the association between cannabis use and psychotic symptoms.

Change in cannabis use in the general population: a longitudinal study on the impact on psychotic experiences

OBJECTIVE

To prospectively assess the relationship between cannabis use and psychotic experiences over time.

METHOD

In a longitudinal design, young adults aged 18-27years (N=705) gave online information on cannabis use and completed the Community Assessment of Psychic Experiences (CAPE). These measures were repeated after an interval ranging from six months to five years.

RESULTS

A decrease in cannabis use was associated with a decrease in total psychotic experiences (β=-0.096, p=0.01) after adjustment for a range of potential confounders. An increase in cannabis use was associated with increased positive symptoms at follow-up (β=0.07, p=0.02), but was not significantly associated with increases in Negative and Depression symptom scores, nor with the total number of psychotic experiences.

CONCLUSION

In the first study to the association of change in cannabis use and psychotic experiences over time in the general population, we found an association between changes in cannabis use and changes in the frequency of psychotic experiences. While this does not prove a causal relationship between cannabis use and psychosis, our findings are consistent with studies suggesting that cessation of cannabis use may be beneficial in terms of reducing psychotic experiences.

Cannabidiol as a potential treatment for psychosis

Although cannabis use is associated with an increased risk of developing psychosis, the cannabis constituent cannabidiol (CBD) may have antipsychotic properties. This review concisely describes the role of the endocannabinoid system in the development of psychosis and provides an overview of currently available animal, human experimental, imaging, epidemiological and clinical studies that investigated the antipsychotic properties of CBD. In this targeted literature review we performed a search for English articles using Medline and EMBASE. Studies were selected if they described experiments with psychosis models, psychotic symptoms or psychotic disorders as outcome measure and involved the use of CBD as intervention. Evidence from several research domains suggests that CBD shows potential for antipsychotic treatment.

Cigarette smoking and cannabis use are equally strongly associated with psychotic-like experiences: a cross-sectional study in 1929 young adults

BACKGROUND

Cannabis use is associated with increased risk for psychotic-like experiences (PLEs) and psychotic disorders. It remains unclear whether this relationship is causal or due to confounding.

METHOD

A total of 1929 young adults aged 18-30 years participated in a nationwide internet-based survey in The Netherlands and gave information on demographics, substance use and parental psychiatric illness and completed the Community Assessment of Psychic Experiences (CAPE).

RESULTS

Cigarette smoking and cannabis use were equally strongly associated with the frequency of PLEs in a fully adjusted model (β = 0.098 and 0.079 respectively, p < 0.05). Cannabis use was associated with distress from PLEs in a model adjusted for an elaborate set of confounders excluding smoking (β = 0.082, p < 0.05). However, when cigarette smoking was included in the model, cannabis use was not a significant predictor of distress from PLEs. Cigarette smoking remained associated with distress from PLEs in a fully adjusted model (β = 0.107, p < 0.001).

CONCLUSIONS

Smoking is an equally strong independent predictor of frequency of PLEs as monthly cannabis use. Our results suggest that the association between moderate cannabis use and PLEs is confounded by cigarette smoking.

Cannabis use as an indicator of risk for mental health problems in adolescents: a population-based study at secondary schools

BACKGROUND

Although the association between cannabis use and a wide range of psychiatric symptoms is fairly well established, it is not clear whether cannabis use is also a risk factor for general mental health problems at secondary school. Method A total of 10 324 secondary school children aged 11-16 years, participating in an ongoing Public Health Service School Survey, gave information on demographics, substance use, school factors and stressful life events and completed the Strengths and Difficulties Questionnaire (SDQ).

RESULTS

Cannabis use in the past month was associated with a clinically relevant score on the SDQ [unadjusted odds ratio (OR) 4.46, 95% confidence interval (CI) 3.46-5.76]. Other risk factors associated with poor psychosocial functioning were: a low level of education, alcohol use, cigarette smoking, hard drug use, frequent truancy, an unfavourable school evaluation, feeling unsafe at school, being victimized, frequent absence due to illness, a mentally ill parent, molestation by a parent, financial problems and feeling distressed by an adverse event. In a full model adjusting for these risk factors, cannabis was not significantly associated with mental health problems, although an association at trend level was apparent. Of these risk factors, regular alcohol use, cigarette smoking, hard drug use, frequent truancy, an unfavourable school evaluation and frequent absence due to illness were also associated with cannabis use.

CONCLUSIONS

The association between cannabis use and poor psychosocial functioning in adolescence is due, at least in part, to confounding by other risk factors. Thus, cannabis use can best be viewed as an indicator of risk for mental health problems in adolescence.

Cannabis use and vulnerability for psychosis in early adolescence--a TRAILS study

AIMS

To examine the direction of the longitudinal association between vulnerability for psychosis and cannabis use throughout adolescence.

DESIGN

Cross-lagged path analysis was used to identify the temporal order of vulnerability for psychosis and cannabis use, while controlling for gender, family psychopathology, alcohol use and tobacco use.

SETTING

A large prospective population study of Dutch adolescents [the TRacking Adolescents' Individual Lives Survey (TRAILS) study].

PARTICIPANTS

A total of 2120 adolescents with assessments at (mean) age 13.6, age 16.3 and age 19.1.

MEASUREMENTS

Vulnerability for psychosis at the three assessment points was represented by latent factors derived from scores on three scales of the Youth Self-Report and the Adult Self-Report, i.e. thought problems, social problems and attention problems. Participants self-reported on cannabis use during the past year at all three waves.

FINDINGS

Significant associations (r = 0.12-0.23) were observed between psychosis vulnerability and cannabis use at all assessments. Also, cannabis use at age 16 predicted psychosis vulnerability at age 19 (Z = 2.6, P < 0.05). Furthermore, psychosis vulnerability at ages 13 (Z = 2.0, P < 0.05) and 16 (Z = 3.0, P < 0.05) predicted cannabis use at, respectively, ages 16 and 19.

CONCLUSIONS

Cannabis use predicts psychosis vulnerability in adolescents and vice versa, which suggests that there is a bidirectional causal association between the two.

Advanced paternal age and vulnerability to psychotic-like experiences in the offspring

OBJECTIVE

To investigate whether advanced paternal age is associated with increased psychotic-like experiences (PLEs) and increased sensitivity to Cannabis in the offspring.

METHODS

A cross-sectional population-based study in 1684 participants aged 18 to 25.

RESULTS

We found no association of paternal age with PLEs. Only the positive dimension subscale was associated to paternal age, but that could be largely contributed to outliers. Also no increased sensitivity to Cannabis smoking was apparent.

CONCLUSION

In the general population, we did not find robust support for an association between paternal age and vulnerability to PLEs in 18-25year old offspring.

Exploration of the comorbidity of cannabis use disorders and mental health disorders among inpatients presenting to all hospitals in New South Wales, Australia

BACKGROUND

Cannabis is one of the most commonly used illegal psychoactive substances and its use often coexists with mental health disorders.

OBJECTIVES

This study explores the relationships between cannabis use disorders and some common mental health disorders.

METHODS

Admissions to all New South Wales (NSW) hospitals were analyzed. The data were extracted from the NSW Department of Health Inpatient Statistics Data Collection for the period 1 July 2006 to 30 June 2007. Readmissions within 28 days were excluded. Data extraction and analyses were performed by using the SAS program. Chi-square tests and odds ratio were used to examine the association between cannabis use disorder and mental health disorders.

RESULTS

Of the 1.8 million admissions, associations between cannabis use disorders and mental health disorders were strong (odds ratio = 7.8-10.7, p < .001). Inpatients (53.8%) who used cannabis had at least one identifiable mental disorder. Higher comorbidity rates were observed for females (39.6%) and for those aged between 30 and 49 years. Cannabis use disorder comorbid with the most common mental disorders were: anxiety disorder (3.4%), bipolar affective disorder (5.7%), major depressive disorder (10.9%), personality disorder (9.2%), schizophrenia (15.0%), and severe stress disorder (8.7%). Cannabis use disorder has strong associations with these mental health disorders (odds ratio 4.8-34.8). The average length of stay (ALOS) for cannabis use disorders was 9.0 days and the ALOS for the most common mental health disorders was 11.0 days.

CONCLUSIONS AND IMPLICATIONS

This study provides detailed information about the association between cannabis use disorders and mental health disorders and extends our understanding of comorbidity presentations in inpatient admissions.

The association between delusional-like experiences, and tobacco, alcohol or cannabis use: a nationwide population-based survey

BACKGROUND

Previous population-based studies have found that delusional-like experiences (DLE) are prevalent in the community, and are associated with a wide range of mental health disorders including substance use. The aim of the study was to explore the association between DLE and three commonly used substances--tobacco, alcohol and cannabis.

METHODS

Subjects were drawn from the Australian National Survey of Mental Health and Wellbeing 2007. The Composite International Diagnostic Interview was used to identify DLE, common psychiatric disorders, and substance use. We examined the relationship between the variables of interest using logistic regression, adjusting for potential confounding factors.

RESULTS

Of 8,773 participants, 8.4% (n=776) subjects endorsed one or more DLE. With respect to tobacco use, compared to nonusers, DLE were more common in those who (a) had daily use, (b) commenced usage aged 15 years or less, and (c) those who smoked heavily (23 or more cigarettes per day). Participants with cannabis use disorders were more likely to endorse DLE; this association was most prominent in those with an onset of 16 years or younger. In contrast, the pattern of association between DLE versus alcohol use or dependence was less consistent, however those with early onset alcohol use disorders were more likely to endorse DLE probe items.

CONCLUSIONS

While cannabis use disorders have been previously linked with DLE, our findings linking alcohol and tobacco use and DLE suggest that the influence of these substances on psychosis-related outcomes warrants closer scrutiny in longitudinal prospective studies.