Age at initiation of cannabis use predicts age at onset of psychosis: the 7- to 8-year trend

Effects of Recreational Cannabis Legalization on Mental Health: Scoping Review

OBJECTIVE

Recreational cannabis legalization (RCL) is expanding rapidly. RCL's effects on mental health issues are of particular concern because cannabis use is more frequent among people receiving psychiatric care and is associated with several psychiatric disorders. The authors conducted a scoping review to examine the evidence and discern gaps in the literature concerning the effects of RCL on mental health and to assess the factors responsible for an observed heterogeneity in research results.

METHODS

This scoping literature review followed PRISMA guidelines. Five databases-MEDLINE, CINAHL, Embase, APA PsycInfo, and Web of Science-were searched for English- or French-language reports published between January 1, 2012, and April 30, 2023.

RESULTS

Twenty-eight studies from the United States and Canada were found. The studies were classified by category of the study's data (patients receiving psychiatric care [k=1], death records [k=4], emergency department or hospital records [k=10], and the general population [k=13]) and by the diagnosis (schizophrenia or psychoses, mood disorders, anxiety disorders and symptoms, suicide or suicidal ideation, or other mental health issues) examined. The review findings revealed a paucity of research and indicated mixed and largely inconclusive results of the studies examined. Research gaps were found in the examination of potential changes in cannabis use patterns among people receiving psychiatric care and in the availability of longitudinal studies.

CONCLUSIONS

Clinicians, researchers, and policy makers need to collaborate to address the research gaps and to develop evidence-based policies that reflect a thorough understanding of the effects associated with RCL.

Age-dependent association of cannabis use with risk of psychotic disorder

BACKGROUND

Epidemiologic research suggests that youth cannabis use is associated with psychotic disorders. However, current evidence is based heavily on 20th-century data when cannabis was substantially less potent than today.

METHODS

We linked population-based survey data from 2009 to 2012 with records of health services covered under universal healthcare in Ontario, Canada, up to 2018. The cohort included respondents aged 12-24 years at baseline with no prior psychotic disorder (N = 11 363). The primary outcome was days to first hospitalization, ED visit, or outpatient visit related to a psychotic disorder according to validated diagnostic codes. Due to non-proportional hazards, we estimated age-specific hazard ratios during adolescence (12-19 years) and young adulthood (20-33 years). Sensitivity analyses explored alternative model conditions including restricting the outcome to hospitalizations and ED visits to increase specificity.

RESULTS

Compared to no cannabis use, cannabis use was significantly associated with psychotic disorders during adolescence (aHR = 11.2; 95% CI 4.6-27.3), but not during young adulthood (aHR = 1.3; 95% CI 0.6-2.6). When we restricted the outcome to hospitalizations and ED visits only, the strength of association increased markedly during adolescence (aHR = 26.7; 95% CI 7.7-92.8) but did not change meaningfully during young adulthood (aHR = 1.8; 95% CI 0.6-5.4).

CONCLUSIONS

This study provides new evidence of a strong but age-dependent association between cannabis use and risk of psychotic disorder, consistent with the neurodevelopmental theory that adolescence is a vulnerable time to use cannabis. The strength of association during adolescence was notably greater than in previous studies, possibly reflecting the recent rise in cannabis potency.

Exploring the relationship between frequent cannabis use, belief updating under uncertainty and psychotic-like symptoms

Background

Cannabis users present an important group for investigating putative mechanisms underlying psychosis, as cannabis-use is associated with an increased risk of psychosis. Recent work suggests that alterations in belief-updating under uncertainty underlie psychosis. We therefore compared belief updating under uncertainty between cannabis and non-cannabis users.

Methods

49 regular cannabis users and 52 controls completed the Space Game, via an online platform used for behavioral testing. In the task, participants were asked to predict the location of the stimulus based on previous information, under different uncertainty conditions. Mixed effects models were used to identify significant predictors of mean score, confidence, performance error and learning rate.

Results

Both groups showed decreased confidence in high noise conditions, and increased belief updating in more volatile conditions, suggesting that they could infer the degree and sources of uncertainty. There were no significant effects of group on any of the performance indices. However, within the cannabis group, frequent users showed worse performance than less frequent users.

Conclusion

Belief updating under uncertainty is not affected by cannabis use status but could be impaired in those who use cannabis more frequently. This finding could show a similarity between frequent cannabis use and psychosis risk, as predictors for abnormal belief-updating.

Stress, Environment and Early Psychosis

Existing literature provides extended evidence of the close relationship between stress dysregulation, environmental insults, and psychosis onset. Early stress can sensitize genetically vulnerable individuals to future stress, modifying their risk for developing psychotic phenomena. Neurobiological substrate of the aberrant stress response to hypothalamic-pituitary-adrenal axis dysregulation, disrupted inflammation processes, oxidative stress increase, gut dysbiosis, and altered brain signaling, provides mechanistic links between environmental risk factors and the development of psychotic symptoms. Early-life and later-life exposures may act directly, accumulatively, and repeatedly during critical neurodevelopmental time windows. Environmental hazards, such as pre- and perinatal complications, traumatic experiences, psychosocial stressors, and cannabis use might negatively intervene with brain developmental trajectories and disturb the balance of important stress systems, which act together with recent life events to push the individual over the threshold for the manifestation of psychosis. The current review presents the dynamic and complex relationship between stress, environment, and psychosis onset, attempting to provide an insight into potentially modifiable factors, enhancing resilience and possibly influencing individual psychosis liability.

Association between Cannabis Use Disorder and Mental Health Disorders in the Adolescent Population: A Cohort Study

INTRODUCTION

According to the literature, early initiation to cannabis use and a dependent pattern of use are important risk factors for the development of mental health disorders. However, there are few cohort studies which look at the development of mental health disorders associated with cannabis use among young people with cannabis use disorder (CUD). The aim of the study was to determine the cumulative incidence of mental health disorders and the risk of developing mental health disorders among minors who commenced treatment for CUD in Catalonia during 2015-2019.

METHODS

This was a retrospective fixed cohort study, matched for confounding variables, based on data from the Catalan Health Surveillance System. The exposed cohort comprised young people who entered treatment for CUD during 2015-2019 (n = 948) and who were minors on the date of commencing treatment. Matching was done with a paired cohort (n = 4,737), according to confounding variables. Individuals with a diagnosis of a mental health disorder prior to the study period were excluded. The cumulative incidence was calculated for mental health disorders for the exposed and the paired cohorts and stratified by type of mental disorder. Incidence rate ratios were estimated using the conditional Poisson model with robust variance, stratified by sex.

RESULTS

The cumulative incidence for development of a mental health disorder was 19.6% in the exposed cohort and 3.1% in the paired cohort; with higher incidence among females (females 32.7%; males 15.8%). The exposed cohort had an 8.7 times increased risk of developing a mental health disorder than the paired cohort. The most frequent diagnoses were reaction to severe stress, adjustment disorder, and personality disorders.

CONCLUSION

This study confirmed that the exposed cohort was at increased risk of developing mental health disorders compared to the paired cohort. To date, few studies have analyzed the association between cannabis use and the development of mental health disorders, considering cannabis dependence. Further studies should be undertaken considering CUD. In addition, more studies are needed to understand the factors that determine the development of CUD. Further research in these areas would contribute to the design of prevention strategies aimed at those young individuals with a higher risk of developing cannabis dependence and suffering its consequences.

Variations of cannabis-related adverse mental health and addiction outcomes across adolescence and adulthood: A scoping review

Introduction

Evidence supporting associations between cannabis use and many health outcomes is growing, however it remains unclear how such associations vary across the lifespan. We therefore aim to answer the following questions: (1) Are the risks of cannabis's adverse effects on mental health and addiction-related outcomes different in adolescents than in adults? (2) What are the relationships between these cannabis's adverse effects and (a) an individual's age at first cannabis use, (b) age at assessment, and (c) duration of cannabis use?

Methods

We searched Medline, Embase, CINAHL, and PsychINFO from inception to 18 October 2021. Two reviewers independently screened studies and descriptively synthesized results.

Results

We included 140 studies. Cannabis effects on mental health and addiction-related outcomes were worse in adolescents, early cannabis initiators and cannabis users who consumed for longest periods. Evidence of worse long-term adverse effects in adolescents was substantial for psychosis, cannabis, and nicotine use disorders; mixed for depression, suicidality, other substance use and disorders; and limited for anxiety. Additionally, acute cannabis exposure had the opposite trend with adults more often reporting adverse effects than adolescents.

Conclusion

The available evidence suggests that cannabis use should be delayed as late as possible in adulthood and shortened in duration across the lifespan to decrease the risk of negative outcomes, while emphasizing the need for adapted harm reduction approaches. This scoping review provides evidence on the role of age and duration of exposure as determinants of cannabis-related adverse effects, which may inform prevention and harm reduction strategies.

Systematic review registration

https://doi.org/10.17605/OSF.IO/BYG72.

Is early exposure to cannabis associated with bipolar disorder? Results from a Finnish birth cohort study

BACKGROUND AND AIMS

There are few longitudinal studies assessing the association of cannabis use and subsequent onset of bipolar disorder. We aimed to measure the association between early cannabis exposure and subsequent bipolar disorder.

DESIGN, SETTING AND PARTICIPANTS

Observational study linking a sample from the northern Finland birth cohort 1986 (n = 6325) to nation-wide register data to examine the association of life-time cannabis exposure at age 15/16 years and subsequent bipolar disorder until age 33 (until the end of 2018); 6325 individuals (48.8% males) were included in the analysis.

MEASUREMENTS

Cannabis exposure was measured via self-report. Bipolar disorder was measured via bipolar disorder-related diagnostic codes (ICD-10: F30.xx, F31.xx) collected from the Care Register for Health Care 2001-18, the Register of Primary Health Care Visits 2011-18, the medication reimbursement register of the Social Insurance Institution of Finland 2001-05 and the disability pensions of the Finnish Center for Pensions 2001-16. Potential confounders included demographic characteristics, parental psychiatric disorders, emotional and behavioral problems and other substance use.

FINDINGS

Three hundred and fifty-two adolescents (5.6%) reported any cannabis use until the age of 15-16 years. Of the whole sample, 66 (1.0%) were diagnosed with bipolar disorder. Adolescent cannabis use was associated with bipolar disorder [hazard ratio (HR) = 3.46; 95% confidence interval (CI) = 1.81-6.61]. This association remained statistically significant after adjusting for sex, family structure and parental psychiatric disorders (HR = 3.00; 95% CI = 1.47-6.13) and after further adjusting for adolescent emotional and behavioral problems (HR = 2.34; 95% CI = 1.11-4.94). Further adjustments for frequent alcohol intoxications, daily smoking and lifetime illicit drug use attenuated the associations to statistically non-significant.

CONCLUSIONS

In Finland, the positive association between early cannabis exposure and subsequent development of bipolar disorder appears to be confounded by other substance use.

Trajectories of adolescent psychotic-like experiences and early cannabis exposure: Results from a Finnish Birth Cohort Study

BACKGROUND

Longitudinal studies examining the effect of cannabis exposure (CE) on the prognosis of adolescents with psychotic-like experiences (PLEs) are scarce. We examined trajectories of mental health in adolescents with PLEs and cannabis exposure.

METHODS

The Northern Finland Birth Cohort 1986 (n = 6552) with linkage to nationwide register data was used. Information on lifetime cannabis exposure was collected when participants were aged 15/16. Register-based outcome data on diagnoses made in clinical practice were obtained until age 33. Logistic regression was used to study the association of PLE/CE patterns and subsequent psychiatric disorders. The group with neither PLEs nor CE was utilized as the reference group. Parental psychiatric disorders, family structure, sex, frequent alcohol intoxications, daily smoking and illicit substance use other than cannabis were adjusted for.

RESULTS

In all, 6552 subjects (49.2 % males) were included in analysis. PLEs with cannabis exposure were associated with any psychiatric disorder (OR = 2.59; 95 % CI 1.82-3.68), psychotic disorders (OR = 3.86; 95 % CI 1.83-8.11), mood disorders (OR 4.07; 95 % CI 2.74-6.04), depressive disorders (OR = 4.35; 95 % CI 2.93-6.48), anxiety disorders (OR = 2.06; 95 % CI 1.34-3.17) and substance use disorders (OR = 2.26; 95 % CI 1.13-4.50) compared to reference group. Effect sizes were greater for group with both PLEs and cannabis use than for group with PLEs only.

CONCLUSIONS

Early-onset cannabis use is an adverse prognostic marker for adolescents with PLEs after extensive confounder control including other substance use.

Adolescent cannabis use and later development of schizophrenia: An updated systematic review of longitudinal studies

BACKGROUND

The study aimed to review recent literature not included in previous reviews and ascertain the correlation between early marijuana use among adolescents, between 12 and 18 years of age, and the development of schizophrenia in early adulthood. A further aim was to determine if the frequency of use of marijuana demonstrated any significant effect on the risk of developing schizophrenia in early adulthood.

METHODS

Five hundred and ninety-one studies were examined; six longitudinal cohort studies were analyzed using a series of nonparametric tests and meta-analysis.

RESULTS

Nonparametric tests, Friedman tests, and Wilcoxon signed tests showed a highly statistically significant difference in odds ratios for schizophrenia between both high- and low-cannabis users and no-cannabis users.

CONCLUSION

Both high- and low-frequency marijuana usage were associated with a significantly increased risk of schizophrenia. The frequency of use among high- and low-frequency users is similar in both, demonstrating statistically significant increased risk in developing schizophrenia.

Lifetime Cannabis Use Is Not Associated With Negative Beliefs About Medication in Patients With First Treatment Psychosis

OBJECTIVE

Cannabis use is common among patients with psychosis, and along with negative beliefs about medication, it has been found to predict poor adherence to antipsychotic drug treatment. Such lack of adherence to antipsychotic drug treatment increases the risk of poor clinical outcomes and relapse in patients with first treatment for psychosis (FTP). However, to date, it is unclear whether cannabis use may be related to negative perceptions about antipsychotic drug treatment.

METHODS

A cross-sectional sample of 265 FTP patients with schizophrenia spectrum disorder underwent extensive clinical assessments. Three measures of cannabis use were obtained: lifetime, current and meeting diagnostic criteria for abuse or addiction. For the primary analyses we focused on lifetime cannabis use. The Beliefs about Medication Questionnaire (BMQ) was employed to assess the patients' specific concerns and perceptions of antipsychotic medications, as well as general beliefs about pharmacotherapy. The relationship between lifetime cannabis use and BMQ scores was investigated with general linear model (GLM) analyses, controlling for age and sex.

RESULTS

Patients with lifetime use of cannabis ≥10 times were more likely to be male, younger at the age of onset of psychosis and with higher levels of alcohol use and daily tobacco smoking, as compared to the non-users (p < 0.05). Neither lifetime use of cannabis, current use nor a cannabis abuse diagnosis was associated with negative beliefs about medicines as measured by the BMQ questionnaire.

CONCLUSION

Use of cannabis is not linked to negative perceptions about antipsychotic medicines in patients with FTP. Other reasons for poor compliance to antipsychotic drug treatment in cannabis users need to be further investigated.

Altered cerebellar-cortical resting-state functional connectivity in cannabis users

BACKGROUND

Cannabis use has been associated with abnormalities in cerebellar mediated motor and non-motor (i.e. cognition and personality) phenomena. Since the cerebellum is a region with high cannabinoid type 1 receptor density, these impairments may reflect alterations of signaling between the cerebellum and other brain regions.

AIMS

We hypothesized that cerebellar-cortical resting-state functional connectivity (rsFC) would be altered in cannabis users, relative to their non-using peers. It was also hypothesized that differences in rsFC would be associated with cannabis use features, such as age of initiation and lifetime use.

METHODS

Cerebellar-cortical and subcortical rsFCs were computed between 28 cerebellar lobules, defined by a spatially unbiased atlas template of the cerebellum, and individual voxels in the cerebral regions, in 41 regular cannabis users (20 female) and healthy non-using peers (N = 31; 18 female). We also investigated associations between rsFC and cannabis use features (e.g. lifetime cannabis use and age of initiation).

RESULTS

Cannabis users demonstrated hyperconnectivity between the anterior cerebellar regions (i.e. lobule I-IV) with the posterior cingulate cortex, and hypoconnectivity between the rest of the cerebellum (i.e. Crus I and II, lobule VIIb, VIIIa, VIIIb, IX, and X) and the cortex. No associations were observed between features of cannabis use and rsFC.

CONCLUSIONS

Cannabis use was associated with altered patterns of rsFC from the cerebellum to the cerebral cortex which may have a downstream impact on behavior and cognition.

Imaging Brain Fatty Acid Amide Hydrolase in Untreated Patients With Psychosis

BACKGROUND

The brain's endocannabinoid system, the primary target of cannabis, has been implicated in psychosis. The endocannabinoid anandamide is elevated in cerebrospinal fluid of patients with schizophrenia. Fatty acid amide hydrolase (FAAH) controls brain anandamide levels; however, it is unknown if FAAH is altered in vivo in psychosis or related to positive psychotic symptoms.

METHODS

Twenty-seven patients with schizophrenia spectrum disorders and 36 healthy control subjects completed high-resolution positron emission tomography scans with the novel FAAH radioligand [¹¹C]CURB and structural magnetic resonance imaging. Data were analyzed using the validated irreversible 2-tissue compartment model with a metabolite-corrected arterial input function.

RESULTS

FAAH did not differ significantly between patients with psychotic disorders and healthy control subjects (F_1,62.85 = 0.48, p = .49). In contrast, lower FAAH predicted greater positive psychotic symptom severity, with the strongest effect observed for the positive symptom dimension, which includes suspiciousness, delusions, unusual thought content, and hallucinations (F_1,26.69 = 12.42, p = .002; Cohen's f = 0.42, large effect). Shorter duration of illness (F_1,26.95 = 13.78, p = .001; Cohen's f = 0.39, medium to large effect) and duration of untreated psychosis predicted lower FAAH (F_1,26.95 = 6.03, p = .021, Cohen's f = 0.27, medium effect). These results were not explained by past cannabis exposure or current intake of antipsychotic medications. FAAH exhibited marked differences across brain regions (F_7,112.62 = 175.85, p < 1 × 10^-56; Cohen's f > 1). Overall, FAAH was higher in female subjects than in male subjects (F_1,62.84 = 10.05, p = .002; Cohen's f = 0.37).

CONCLUSIONS

This first study of brain FAAH in psychosis indicates that FAAH may represent a biomarker of disease state of potential utility for clinical studies targeting psychotic symptoms or as a novel target for interventions to treat psychotic symptoms.

Examining which factors influence age of onset in males and females with schizophrenia

OBJECTIVE

Data from the 2010 Australian National Survey of High Impact Psychosis (SHIP) was used to examine (1) what variables influence age of onset (AOO) for males and females, and (2) whether influencing variables were different between the sexes.

METHOD

Data from 622 schizophrenia patients in the SHIP sample was used. These included early life factors, encompassing family psychiatric history, childhood development, trauma and parental loss. Factors occurring within 12 months of diagnosis were also used, including drug/alcohol abuse and premorbid work and social adjustment. Based on the recognised differences in symptom profiles and AOO between the sexes, these factors were regressed separately for males and females.

RESULTS

Stepwise linear regressions showed that a family history of psychiatric disorders was significantly associated with earlier AOO in both sexes. Other variables differed between males and females. Specifically, for females, an earlier AOO was associated with poor premorbid social adjustment and the loss of a family member in childhood. Older AOO was associated with immigrant status. For males, a younger AOO was associated with unemployment at onset, poor premorbid work adjustment, parental divorce in childhood, and lifetime cannabis use. A higher premorbid IQ was associated with an older AOO.

CONCLUSION

Familial predisposition to psychiatric illness is related to earlier AOO of schizophrenia independent of sex. Males appear to have more individual-based predictive factors while females seem to have more community/social-based influences. Future directions for research in schizophrenia are suggested.

Prevalence and Correlates of Psychotic Like Experiences in a Large Community Sample of Young Adults in Tunisia

Despite the increased focus on non-clinical psychosis populations, no community surveys have properly investigated the phenotypal expression of Psychotic like experiences (PLEs) in the Arab-Muslim world. We aimed to examine the prevalence and correlates of PLEs in a large sample of Tunisian college students. A total of 1489 students (64.3% female, aged 18-40) participated in a cross-sectional survey. The Positive Subscale of Community Assessment of Psychotic Experiences was used to measure PLEs. The rates of PLEs found in our work were relatively high compared with those found in previous international studies, with 51.4% of the participants reporting at least one positive PLE 'nearly-always'. After controling for confounding variables, other drug use in the past year represented the only substance use variable among the significant predictors in the final model. Our findings should raise awareness of the need for implementing an early intervention programs in our region.

Assessing the public health impact of cannabis legalization in Canada: core outcome indicators towards an 'index' for monitoring and evaluation

The legalization of non-medical cannabis use and supply is impending in Canada. This constitutes a major policy change with the declared objective of improving public health outcomes, which requires rigorous monitoring and evaluation. While numerous different aspects associated with legalization will be examined, a focused perspective is required for effective policy evaluation purposes. To these ends, we have identified a set of 10 core indicators associated with cannabis-related risk/harm outcomes-based on current best evidence-that are expected to measure the primary impacts of legalization on public health outcomes. We briefly review these indicators, and their respective data availability in Canada. As ideally an integrated outcome assessment of cannabis legalization's impact on public health will be available, we further propose options to merge the individual indicators into an integrated, weighted 'index', considering their expected relative impact for public health. One possible approach to undertake this is 'multi-criteria decision analysis' as a method to weight the relative indicator impact on public health; alternative approaches are proposed. The integrated 'public health index' for cannabis legalization will allow for scientifically comprehensive, while focused, monitoring and evaluation of the effects of legalization in Canada for the benefits of science and evidence-based policy alike.

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.

Neighborhood-level predictors of age at onset and duration of untreated psychosis in first-episode psychotic disorders

OBJECTIVE

Recent years have witnessed growing interest in the role of the social environment in the development and outcomes of schizophrenia. We investigated whether neighborhood characteristics are associated with two important prognostic factors in early-course psychosis, age at onset of psychosis (AOP) and duration of untreated psychosis (DUP).

METHODS

Data were collected from patients admitted to the hospital for first-episode schizophrenia-spectrum disorder. We collected data on perceived neighborhood disorder during childhood/adolescence and extracted data on 13 neighborhood characteristics from the American Community Survey based upon individual addresses. Four neighborhood-level factors were derived from factor analysis. Multiple logistic regression analyses assessed the association between specific neighborhood characteristics and the two prognostic factors (earlier AOP and longer DUP) in early-course psychosis.

RESULTS

143 participants had valid addresses geo-coded. Neighborhood-level residential instability was associated with an earlier AOP (OR = 1.760; p = 0.022) even after controlling for known risk factors (OR = 2.026; p = 0.020) and also after controlling for individual-level residential instability (OR = 1.917; p = 0.037). The general socioeconomic status neighborhood factor (OR = 1.119; p = 0.019) and perceived neighborhood disorder (OR = 1.075; p = 0.005) were associated with a longer DUP. But only perceived neighborhood disorder (OR = 1.146; p = 0.011) remained significant, and general socioeconomic status was close to significant (OR = 1.215; p = 0.062), after controlling for individual-level predictors and socioeconomic status.

CONCLUSIONS

This study found evidence that neighborhood-level characteristics (in this case, residential instability) may be associated with earlier AOP, and perceptions of neighborhood disorder are associated with a longer treatment delay. Socioenvironmental factors should be more consistently considered going forward in research on early psychotic disorders.

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.

[Cannabis use in subjects at ultra high risk for psychosis]

Cannabis use is widespread among people at ultra-high risk (UHR) for psychosis. The causal link as well as the temporal link between cannabis use and further occurrence of psychosis in UHR people remain inconclusive. Current science data supported an increased risk of transition to psychosis in cannabis users who are genetically predisposed to psychosis. This risk would be even greater in the presence of a family history of psychosis, in case of a strong use and an early onset use. Several models have been cited to explain the link between cannabis use and the subsequent onset of psychosis or prepsychotic states: cannabis-induced modifications of some brain structures, a dysregulation of the hypothalamic-pituitary axis and an alteration of normal neurological development via the endocannabinoid system. Cannabis represents a modifiable risk for psychosis. Current interventions aim to reduce or stop the cannabis use in order to reduce the risk of transition to psychosis.

Maternal Cannabis Use During a Child's Lifetime Associated With Earlier Initiation

INTRODUCTION

Earlier cannabis initiation is associated with more severe neuropsychiatric and social consequences. The authors investigated whether mothers' cannabis use is associated with earlier cannabis initiation by their children.

METHODS

Mother and child data were from the National Longitudinal Survey of Youth 1979 (1980-1998 waves) and Child and Young Adults (1988-2014 waves) cohorts, respectively. Cox proportional hazard models assessed the effect of maternal cannabis use prior to a child's adolescence on the child's risk of subsequent cannabis initiation. Models were stratified by race and child's age category (6-16, 17-24, ≥25 years). Adjusted analyses controlled for sociodemographic variables. Analyses were conducted in 2017.

RESULTS

Median age of cannabis initiation for children of maternal ever users was age 16years compared with age 18years among children of maternal never users. Children of 1-year and multiple-year users were at increased risk of cannabis initiation between ages 6 and 16years (hazard ratio=1.38, p<0.001, and hazard ratio = 1.45, p<0.001, respectively). Effects were slightly stronger among non-Hispanic non-black children.

CONCLUSIONS

As cannabis legalization expands across the U.S., adult use may become increasingly normative. This study indicates that maternal cannabis use may be a risk factor for early initiation among their offspring. Preventive interventions should consider strategies to delay initiation among children of cannabis users.

Gene-environment interplay in the etiology of psychosis

Schizophrenia and other types of psychosis incur suffering, high health care costs and loss of human potential, due to the combination of early onset and poor response to treatment. Our ability to prevent or cure psychosis depends on knowledge of causal mechanisms. Molecular genetic studies show that thousands of common and rare variants contribute to the genetic risk for psychosis. Epidemiological studies have identified many environmental factors associated with increased risk of psychosis. However, no single genetic or environmental factor is sufficient to cause psychosis on its own. The risk of developing psychosis increases with the accumulation of many genetic risk variants and exposures to multiple adverse environmental factors. Additionally, the impact of environmental exposures likely depends on genetic factors, through gene-environment interactions. Only a few specific gene-environment combinations that lead to increased risk of psychosis have been identified to date. An example of replicable gene-environment interaction is a common polymorphism in the AKT1 gene that makes its carriers sensitive to developing psychosis with regular cannabis use. A synthesis of results from twin studies, molecular genetics, and epidemiological research outlines the many genetic and environmental factors contributing to psychosis. The interplay between these factors needs to be considered to draw a complete picture of etiology. To reach a more complete explanation of psychosis that can inform preventive strategies, future research should focus on longitudinal assessments of multiple environmental exposures within large, genotyped cohorts beginning early in life.

Age of Cannabis Use Onset and Adult Drug Abuse Symptoms: A Prospective Study of Common Risk Factors and Indirect Effects

The present study examined 1) whether the associations between cannabis use (CU) age of onset and drug abuse by 28 y remain when controlling for risk factors in childhood, adolescence and early adulthood; and 2) the developmental pathways from early risk factors to drug abuse problems. Participants from a longitudinal sample of boys of low socioeconomic status ( N = 1,030) were followed from 6 to 28 y. We examined the self-reported CU onset between the ages of 13 and 17 y and drug abuse symptoms by 28 y. The odds of developing any drug abuse symptoms by 28 y were reduced by 31% for each year of delayed CU onset (OR = 0.69). Cannabis, alcohol and other drug frequency at 17 y mediated this association. Still, even when taking that frequency of use into account, adolescents who started using cannabis before 15 y were at a higher risk of developing drug abuse symptoms by age 28 y. Significant indirect effects were found from early adolescent delinquency and affiliation with deviant friends to drug abuse symptoms at 28 y through CU age of onset and substance use frequency at 17 y. The results suggest more clearly than before that prevention programs should aim at delaying CU onset to prevent or reduce drug abuse in adulthood. Furthermore, prevention programs targeting delinquency and/or affiliation with deviant friends in childhood or early adolescence could indirectly reduce substance abuse in adulthood without addressing substance use specifically.

Is there a common vulnerability in cannabis phenomenology and schizotypy? The role of the N170 ERP

Cannabis use is a known risk factor for the development of psychosis, although the precise nature of this relationship is unclear. The phenomenological experiences associated with cannabis use vary dramatically, and for some resemble certain features of psychosis. We hypothesized that individuals who report particularly unusual experiences associated with cannabis use would demonstrate similar electrophysiological patterns to those who score high on schizotypal personality traits. The Cannabis Experiences Questionnaire (CEQ) and the Schizotypal Personality Questionnaire (SPQ) were used to measure these experiences and traits. A sample of 97 individuals were placed into one of three experimental or two control groups based on their questionnaire scores. These were the "High CEQ", "High SPQ", "High on Both", "Average Users" and "Control" (non-using) groups. Participants completed a visual face perception task. Electroencephalography was used to measure the neural response to the stimuli. The N170 event-related potential (ERP) was used to measure perceptual encoding of the stimulus. The experimental groups elicited significantly reduced N170 ERPs compared to the Control group. The Average User group did not significantly differ from the Control group, and approached significance with the High SPQ group. None of the high scoring groups significantly differed in N170 ERP response from each other. Replicating past research, the CEQ and SPQ scales moderately correlated with each other. The attenuated N170 ERP demonstrated by the high scoring experimental groups may reflect a manifestation of an underlying shared vulnerability.

Association of Substance Use Disorders With Conversion From Schizotypal Disorder to Schizophrenia

IMPORTANCE

Understanding the role of substance use disorders in conversion from schizotypal disorder to schizophrenia may provide physicians and psychiatrists with important tools for prevention or early detection of schizophrenia.

OBJECTIVE

To investigate whether substance use disorders, in particular cannabis use disorder, are associated with conversion to schizophrenia in individuals with schizotypal disorder.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study included a population-based sample of all individuals born in Denmark from January 1, 1981, through August 10, 2014, with an incident diagnosis of schizotypal disorder and without a previous diagnosis of schizophrenia. Follow-up was completed on August 10, 2014, and data were analyzed from March 10, 2017, through February 15, 2018.

EXPOSURES

Information on substance use disorders combined from 5 different registers.

MAIN OUTCOMES AND MEASURES

Cox proportional hazards regression using time-varying information on substance use disorders and receipt of antipsychotics and adjusted for parental history of mental disorders, sex, birth year, and calendar year were used to estimate hazard ratios (HRs) and 95% CIs for conversion to schizophrenia.

RESULTS

A total of 2539 participants with incident schizotypal disorder were identified (1448 men [57.0%] and 1091 women [43.0%]; mean [SD] age, 20.9 [4.4] years). After 2 years, 16.3% (95% CI, 14.8%-17.8%) experienced conversion to schizophrenia. After 20 years, the conversion rate was 33.1% (95% CI, 29.3%-37.3%) overall and 58.2% (95% CI, 44.8%-72.2%) among those with cannabis use disorders. In fully adjusted models, any substance use disorder was associated with conversion to schizophrenia (HR, 1.34; 95% CI, 1.11-1.63). When data were stratified by substance, cannabis use disorders (HR, 1.30; 95% CI, 1.01-1.68), amphetamine use disorders (HR, 1.90; 95% CI, 1.14-3.17), and opioid use disorders (HR, 2.74; 95% CI, 1.38-5.45) were associated with conversion to schizophrenia. These associations were not explained by concurrent use of antipsychotics, functional level before incident schizotypal disorder, or parental history of mental disorders.

CONCLUSIONS AND RELEVANCE

Substance use disorders, in particular cannabis, amphetamines, and opioids, may be associated with conversion from schizotypal disorder to schizophrenia. However, conversion rates are high even in those without substance use disorders, indicating a need for universal and substance-targeted prevention in individuals with schizotypal disorder.

Interactions Between Variation in Candidate Genes and Environmental Factors in the Etiology of Schizophrenia and Bipolar Disorder: a Systematic Review

Schizophrenia and bipolar disorder (BD) are complex and multidimensional disorders with high heritability rates. The contribution of genetic factors to the etiology of these disorders is increasingly being recognized as the action of multiple risk variants with small effect sizes, which might explain only a minor part of susceptibility. On the other site, numerous environmental factors have been found to play an important role in their causality. Therefore, in recent years, several studies focused on gene × environment interactions that are believed to bridge the gap between genetic underpinnings and environmental insults. In this article, we performed a systematic review of studies investigating gene × environment interactions in BD and schizophrenia spectrum phenotypes. In the majority of studies from this field, interacting effects of variation in genes encoding catechol-O-methyltransferase (COMT), brain-derived neurotrophic factor (BDNF), and FK506-binding protein 5 (FKBP5) have been explored. Almost consistently, these studies revealed that polymorphisms in COMT, BDNF, and FKBP5 genes might interact with early life stress and cannabis abuse or dependence, influencing various outcomes of schizophrenia spectrum disorders and BD. Other interactions still require further replication in larger clinical and non-clinical samples. In addition, future studies should address the direction of causality and potential mechanisms of the relationship between gene × environment interactions and various categories of outcomes in schizophrenia and BD.

The link between schizophrenia and substance use disorder: A unifying hypothesis

Substance use disorders occur commonly in patients with schizophrenia and dramatically worsen their overall clinical course. While the exact mechanisms contributing to substance use in schizophrenia are not known, a number of theories have been put forward to explain the basis of the co-occurrence of these disorders. We propose here a unifying hypothesis that combines recent evidence from epidemiological and genetic association studies with brain imaging and pre-clinical studies to provide an updated formulation regarding the basis of substance use in patients with schizophrenia. We suggest that the genetic determinants of risk for schizophrenia (especially within neural systems that contribute to the risk for both psychosis and addiction) make patients vulnerable to substance use. Since this vulnerability may arise prior to the appearance of psychotic symptoms, an increased use of substances in adolescence may both enhance the risk for developing a later substance use disorder, and also serve as an additional risk factor for the appearance of psychotic symptoms. Future studies that assess brain circuitry in a prospective longitudinal manner during adolescence prior to the appearance of psychotic symptoms could shed further light on the mechanistic underpinnings of these co-occurring disorders while identifying potential points of intervention for these difficult-to-treat co-occurring disorders.

Men and women with psychosis and the impact of illness-duration on sex-differences: The second Australian national survey of psychosis

We aimed to examine and compare sex-differences in people receiving treatment for psychotic illnesses in community settings, based on long or short duration of illness; expecting association between longer illness-duration and worse outcomes in women and men. Clinical, demographic and service-use data from the Survey of High Impact Psychosis were analysed by sex and duration of illness (≤5 years; ≥6 years), using independent t-tests, chi-square tests, one-way ANOVA, and Cramer's V. Of the 1825 participants, 47% had schizophrenia, 17.5% bipolar and 16.1% schizo-affective disorders. More women than men had undertaken post-school education, maintained relationships, and been living in their own homes. Women with a shorter-illness-duration showed social functioning equivalent to non-ill women in the general population. Men tended to have an early illness onset, show premorbid dysfunction, be single, show severe disability, and to use illicit substances. Men with a longer-illness-duration were very socially disadvantaged and isolated, often experiencing homelessness and substance use. Men with a short-illness-duration were most likely to be in paid employment, but two-thirds earned less than $AUD500 per fortnight. Men with longer-illness-duration showed most disability, socially and globally. Interventions should be guided by diagnosis, but also by a person's sex and duration of illness.

The consequences of chronic cannabis smoking in vulnerable adolescents

Cannabis, like the mythic shape-shifter, presents in various guises, morphing with the perspective and context of the observer. Arguments about cannabis are confused by a myriad of debates-medical, social, ethical and political-as if a single conceptual umbrella can capture the variety and granularity of marijuana-related issues. This paper responds to marijuana use as it is commonly practised by youth in Australia. It has little to say about synthetic cannabinoids, specific medicinal cannabinoids, or medicinal properties of marijuana. We address those adolescents genetically and environmentally vulnerable to mental illness, with specific emphasis on indigenous and neurodevelopmentally impaired young people who show patterns of usage and response very different to adults and more resilient members of the population. Specifically, the practice of mixing tobacco with marijuana by aboriginal youth, and the resultant coalition of dependencies, will likely presage a rise in pulmonary and central nervous system pathology over the coming decades. Aboriginal youth begin using earlier, persist longer, and take greater quantities of cannabis than non-indigenous youth. This paper recommends practical interventions to reduce the multiple health consequences of chronic cannabis use in young people, especially indigenous young people.

Substance use in youth at risk for psychosis

BACKGROUND

People with schizophrenia have high rates of substance use which contributes to co-morbidity and premature mortality. Some evidence suggests people at-risk for psychosis have high rates of substance use. We aimed to assess substance use in a help-seeking cohort, comparing those at-risk and not at-risk for psychosis, and to establish any relationship with clinical symptoms.

METHOD

Participants were help-seeking youth presenting to mental health services in Sydney and Melbourne. 279 (34.8%) were at-risk for psychosis, and 452 (56.4%) did not meet criteria for a psychotic disorder or risk for psychosis. The excluded individuals were made up of 59 (7.4%) young people who met criteria for a psychotic disorder and 11 (1.4%) who were unable to be evaluated. We assessed the association of substance use involvement with risk status and clinical symptoms using multivariate regression.

RESULTS

Individuals at-risk for psychosis had significantly higher tobacco, alcohol and cannabis use than those not at-risk. Multivariate analysis revealed at-risk status was significantly associated with higher alcohol involvement scores when adjusting for age and gender, but no association was found for cannabis or tobacco. At-risk status was no longer associated with alcohol involvement when cannabis or tobacco use was added into the analysis.

CONCLUSION

Tobacco smoking, alcohol consumption and cannabis use are common in help-seeking youth, particularly those at-risk for psychosis. It is important to consider co-occurring use of different substances in adolescents. Early substance misuse in this phase of illness could be targeted to improve physical and mental health in young people.

Responding to challenges for people with psychotic illness: Updated evidence from the Survey of High Impact Psychosis

OBJECTIVE

The objective is to summarise recent findings from the 2010 Australian Survey of High Impact Psychosis (SHIP) and examine their implications for future policy and planning to improve mental health, physical health and other circumstances of people with a psychotic disorder.

METHODS

Survey of High Impact Psychosis collected nationally representative data on 1825 people with psychotic illness. Over 60 papers have been published covering key challenges reported by participants: financial problems, loneliness and social isolation, unemployment, poor physical health, uncontrolled symptoms of mental illness, and lack of stable, suitable housing. Findings are summarised under the rubric of participant-ranked top challenges.

RESULTS

The main income source for the majority (85%) of participants was a government benefit. Only one-third was employed, and the most appropriate employment services for this group were under-utilised. High rates of loneliness and social isolation impacted mental and physical health. The rate of cardiometabolic disease was well above the general population rate, and associated risk factors were present from a very young age. Childhood abuse (30.6%), adult violent victimisation (16.4%) and alcohol and substance abuse/dependence (lifetime rates of 50.5% and 54.5%, respectively) complicated the clinical profile. Treatment with medication was suboptimal, with physical health conditions undertreated, a high rate of psychotropic polypharmacy and underutilisation of clozapine in chronic persistent psychotic illness. Only 38.6% received evidence-based psychosocial therapies. In the previous year, 27.4% had changed housing and 12.8% had been homeless, on average for 155 days.

CONCLUSION

Money, social engagement and employment are the most important challenges for people with psychotic illness, as well as good physical and mental health. An integrated approach to recovery is needed to optimise service delivery and augment evidence-based clinical practice with measures to improve physical health and social circumstances. Meeting these challenges has the potential to reduce costs to government and society, as well as promote recovery.

Cannabis use related to early psychotic onset: Role of premorbid function

The present cross-sectional study investigates the relation between Cannabis and the development of a psychotic disorder. The main objective is to explore the relations between Cannabis use and psychosis onset, premorbid adjustment cognitive impairment and familiarity. Forty-three patients with a diagnosis of Psychotic Disorder were recruited and divided in two groups based on Cannabis use before onset: Cannabis-using patients (PCU, N=21) and Cannabis-free patients (PCF, N=22). Cognitive functioning was evaluated by Trail Making Test A and B (TMT), Rey-Osterrieth Complex Figure Test (ROCF), and the Rey Auditory-Verbal Learning Test (RAVLT). Premorbid functioning was assessed retrospectively through the Premorbid Adjustment Scale (PAS). PCU group showed earlier onset of the psychotic disorder compared to PCF (p=0.008). This finding was not influenced by age or positive family history for psychiatric illness. PCU subjects showed a worse premorbid functioning respect to PCF and this difference was found to impact on the early onset in the PCU group. In conclusion the present study suggests the hypothesis of an interactive role of Cannabis and poor premorbid school adjustment in the development of psychotic disorders.

Cannabis and development of dual diagnoses: A literature review

BACKGROUND

The use of cannabis has garnered more attention recently with ongoing efforts at marijuana legalization. The consequences of cannabis use are not clearly understood and remain a concern.

OBJECTIVES

To review the acute and persistent effects of cannabis use and associations with psychiatric disorders.

METHODS

Using Pubmed and PsychInfo, we conducted a narrative review of the literature on cannabis and psychiatric comorbidity using the keywords cannab*, marijuana, schizo*, psychosis, mood, depression, mania, bipolar, and anxiety.

RESULTS

There is substantial evidence of cannabis use leading to other illicit drug use and of an association between cannabis use and psychosis. A few reports suggest an association with bipolar disorder while the association with depression and anxiety disorders is mixed.

CONCLUSIONS

Whenever an association is observed between cannabis use and psychiatric disorders, the relationship is generally an adverse one. Age at the time of cannabis use appears to be an important factor with stronger associations observed between adolescent onset cannabis use and later onset of psychiatric disorders. Additional studies taking into account potential confounds (such as withdrawal symptoms, periods of abstinence, and other substance use) and moderators (such as age of initiation of cannabis use, the amount and frequency of drug use, prior history of childhood maltreatment, and gender) are needed to better understand the psychiatric consequences of cannabis use.

Differential effects of childhood trauma and cannabis use disorders in patients suffering from schizophrenia

BACKGROUND

Childhood trauma (CT) and cannabis use are both environmental and modifier risk factors for schizophrenia. However, little is known about how they interact in schizophrenia. We examined the main effect of each of these two environmental factors on the clinical expression of the disease using a large set of variables, and we tested whether and how cannabis and CT interact to influence the course and the presentation of the illness.

METHODS

A sample of 366 patients who met the DSM-IV-TR criteria for schizophrenia was recruited through the FACE-SCZ (Fondamental Advanced Centre of Expertise - Schizophrenia) network. Patients completed a large standardized clinical evaluation including Structured Clinical Interview for DSM Disorders-I (SCID-I), Positive and Negative Symptoms Scale (PANSS), Columbia-Suicide Severity Rating Scale (C-SSRS), Global Assessment of Functioning (GAF), Short-Quality of Life-18 (S-QoL-18), and Medication Adherence Rating Scale (MARS). We assessed CT with the Childhood Trauma Questionnaire and cannabis status with SCID-I.

RESULTS

CT significantly predicted the number of hospitalizations, GAF, and S-QoL-18 scores, as well as the PANSS total, positive, excitement, and emotional distress scores. Cannabis use disorders significantly predicted age of onset, and MARS. There was no significant interaction between CT and cannabis use disorders. However, we found evidence of a correlation between these two risk factors.

CONCLUSIONS

CT and cannabis both have differential deleterious effects on clinical and functional outcomes in patients with schizophrenia. Our results highlight the need to systematically assess the presence of these risk factors and adopt suitable therapeutic interventions.

Clinical Characteristics and Predictors of Outcome of Schizophrenia-Spectrum Psychosis in Children and Adolescents: A Systematic Review

OBJECTIVE

Treatment of early-onset schizophrenia spectrum psychosis (EOS) is hampered by limited data on clinical presentation and illness course. We aimed to systematically review the clinical characteristics, diagnostic trajectories, and predictors of illness severity and outcomes of EOS.

METHODS

We conducted a systematic PubMed, PsycINFO, and Embase literature review including studies published from January 1, 1990 to August 8, 2014 of EOS patients with 1) ≥50% nonaffective psychosis cases; 2) mean age of subjects <19 years; 3) clinical samples recruited through mental health services; 4) cross-sectional or prospective design; 5) ≥20 participants at baseline; 6) standardized/validated diagnostic instruments; and 7) quantitative psychotic symptom frequency or severity data. Exploratory analyses assessed associations among relevant clinical variables.

RESULTS

Across 35 studies covering 28 independent samples (n = 1506, age = 15.6 years, age at illness onset = 14.5 years, males = 62.3%, schizophrenia-spectrum disorders = 89.0%), the most frequent psychotic symptoms were auditory hallucinations (81.9%), delusions (77.5%; mainly persecutory [48.5%], referential [35.1%], and grandiose [25.5%]), thought disorder (65.5%), bizarre/disorganized behavior (52.8%), and flat or blunted affect/negative symptoms (52.3%/50.4%). Mean baseline Positive and Negative Syndrome Scale (PANSS)-total, positive, and negative symptom scores were 84.5 ± 10.9, 19.3 ± 4.4 and 20.8 ± 2.9. Mean baseline Clinical Global Impressions-Severity and Children's Global Assessment Scale/Global Assessment of Functioning (CGAS/GAF) scores were 5.0 ± 0.7 and 35.5 ± 9.1. Comorbidity was frequent, particularly posttraumatic stress disorder (34.3%), attention-deficit/hyperactivity and/or disruptive behavior disorders (33.5%), and substance abuse/dependence (32.0%). Longer duration of untreated psychosis (DUP) predicted less CGAS/GAF improvement (p < 0.0001), and poor premorbid adjustment and a diagnosis of schizophrenia predicted less PANSS negative symptom improvement (p = 0.0048) at follow-up. Five studies directly comparing early-onset with adult-onset psychosis found longer DUP in EOP samples (18.7 ± 6.2 vs. 5.4 ± 3.1 months, p = 0.0027).

CONCLUSIONS

EOS patients suffer substantial impairment from significant levels of positive and negative symptoms. Although symptoms and functioning improve significantly over time, pre-/and comorbid conditions are frequent, and longer DUP and poorer premorbid adjustment is associated with poorer illness outcome.

Marijuana use in the immediate 5-year premorbid period is associated with increased risk of onset of schizophrenia and related psychotic disorders

OBJECTIVES

Several studies suggest that adolescent marijuana use predicts earlier age at onset of schizophrenia, which is a crucial prognostic indicator. Yet, many investigations have not adequately established a clear temporal relationship between the use and onset.

METHODS

We enrolled 247 first-episode psychosis patients from six psychiatric units and collected data on lifetime marijuana/alcohol/tobacco use, and ages at onset of prodrome and psychosis in 210 of these patients. Cox regression (survival analysis) was employed to quantify hazard ratios (HRs) for effects of diverse premorbid use variables on psychosis onset.

RESULTS

Escalation of premorbid use in the 5years prior to onset was highly predictive of an increased risk for onset (e.g., increasing from no use to daily use, HR=3.6, p<0.0005). Through the analysis of time-specific measures, we determined that daily use approximately doubled the rate of onset (HR=2.2, p<0.0005), even after controlling for simultaneous alcohol/tobacco use. Building on previous studies, we were able to determine that cumulative marijuana exposure was associated with an increased rate of onset of psychosis (p=0.007), independent of gender and family history, and this is possibly the reason for age at initiation of marijuana use also being associated with rate of onset in this cohort.

CONCLUSIONS

These data provide evidence of a clear temporal relationship between escalations in use in the five years pre-onset and an increased rate of onset, demonstrate that the strength of the association is similar pre- and post-onset of prodromal symptoms, and determine that early adult use may be just as important as adolescent use in these associations.

Commentary: Adolescent Marijuana Use and Mental Health Amidst a Changing Legal Climate

OBJECTIVE

The purpose of this commentary was to briefly summarize the literature on the relationship between adolescent marijuana use and mental health and how policy changes surrounding marijuana decriminalization and legalization might impact this relationship. 

METHODS

 A comprehensive literature search on adolescent marijuana use, mental health, and the impact of decriminalization and legalization was conducted. Findings are briefly summarized and discussed. 

RESULTS

 Although there is a great deal of ambiguity regarding the causal direction of marijuana use and mental health problems, what can safely be gleaned from this body of research is that early and frequent use of marijuana during adolescence is associated with the development of more psychiatric-related problems than occasional use or nonuse. 

CONCLUSIONS

 Until there is greater clarity in this domain, clinicians should continue to screen adolescent patients for marijuana use as well as mental health difficulties, but may need to be more thoughtful about screening among early adolescents, if in fact a shift in the age of marijuana uptake occurs amidst policy changes.

Cannabis use is associated with 3years earlier onset of schizophrenia spectrum disorder in a naturalistic, multi-site sample (N=1119)

BACKGROUND

Patients with schizophrenia spectrum disorders and substance use may have an earlier onset of illness compared to those without substance use. Most previous studies have, however, too small samples to control for confounding variables and the effect of specific types of substances. The present study aimed to examine the relationship between substance use and age at onset, in addition to the influence of possible confounders and specific substances, in a large and heterogeneous multisite sample of patients with schizophrenia spectrum disorders.

METHODS

The patients (N=1119) were recruited from catchment areas in Oslo, Stavanger and Bergen, Norway, diagnosed according to DSM-IV and screened for substance use history. Linear regression analysis was used to examine the relationship between substance use and age at onset of illness.

RESULTS

Patients with substance use (n=627) had about 3years earlier age at onset (23.0years; SD 7.1) than the abstinent group (n=492; 25.9years; SD 9.7). Only cannabis use was statistically significantly related to earlier age at onset. Gender or family history of psychosis did not influence the results.

CONCLUSION

Cannabis use is associated with 3years earlier onset of psychosis.

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.

No additive effect of cannabis on cognition in schizophrenia

BACKGROUND

We aimed to examine the association between lifetime cannabis use and estimates of both premorbid and current cognitive function in psychotic disorders in an Australian cohort.

METHODS

In an Australian multicenter cohort, 1237 participants with an established ICD-10 diagnosis of psychotic disorder were categorised according to history of lifetime cannabis use (non-users, n=354; cannabis users, n=221; cannabis dependency, n=662). Groups were analyzed according to available indices of cognitive ability: the National Adult Reading Test - Revised (NART-R) for ability prior to illness onset; and the Digit Symbol Coding Test (DSCT) for current ability. Two-way analysis of variance was conducted without any covariate, followed by a two-way analysis of covariance (using age, age at onset of psychiatric illness, premorbid IQ and the Socio-Economic Index for Areas (SEIFA) rankings).

RESULTS

Whilst there appeared to be a significant association between cannabis use and mean DSCT (higher DSCT scores in cannabis using groups) F(2,1080)=9.478, p<0.001, η2=0.017), once covariates were used in the analysis there were no significant differences between groups in mean DSCT scores (F(2,1011)=0.929, p=0.395, η2=0.002). Similarly there were no differences between groups in mean NART scores once, age, age at illness onset and SEIFA rankings were used as covariates (F(2,1032)=1.617, p=0.199, η2=0.003).

CONCLUSIONS

Confounding variables underpin the association between cannabis use and cognitive function in psychotic disorders. Taken together, it would appear that cannabis use or dependence has no additive effect on cognitive dysfunction in these disorders.

Chronic adolescent marijuana use as a risk factor for physical and mental health problems in young adult men

Some evidence suggests that youth who use marijuana heavily during adolescence may be particularly prone to health problems in later adulthood (e.g., respiratory illnesses, psychotic symptoms). However, relatively few longitudinal studies have prospectively examined the long-term physical and mental health consequences associated with chronic adolescent marijuana use. The present study used data from a longitudinal sample of Black and White young men to determine whether different developmental patterns of marijuana use, assessed annually from early adolescence to the mid-20s, were associated with adverse physical (e.g., asthma, high blood pressure) and mental (e.g., psychosis, anxiety disorders) health outcomes in the mid-30s. Analyses also examined whether chronic marijuana use was more strongly associated with later health problems in Black men relative to White men. Findings from latent class growth curve analysis identified 4 distinct subgroups of marijuana users: early onset chronic users, late increasing users, adolescence-limited users, and low/nonusers. Results indicated that the 4 marijuana use trajectory groups were not significantly different in terms of their physical and mental health problems assessed in the mid-30s. The associations between marijuana group membership and later health problems did not vary significantly by race. Findings are discussed in the context of a larger body of work investigating the potential long-term health consequences of early onset chronic marijuana use, as well as the complications inherent in studying the possible link between marijuana use and health effects.

Illness characteristics and symptoms in an Irish early intervention for psychosis service

OBJECTIVES

Study of illness characteristics and symptoms in a young population with psychosis can assist for understanding of their needs, and can inform service planning strategies. The aims of the current study were to describe illness characteristics and symptoms of a first episode psychosis (FEP) sample aged 25 years and under, and compare with a sample aged over 25 years.

METHODS

Interviews were conducted for 437 individuals aged 16-65 years presenting with suspected psychosis between 2005 and 2012 in a defined catchment area (population of 390 000) using the Structured Clinical Interview for DSM IV to determine the presence of a psychosis diagnosis. Individuals with confirmed psychosis were assessed using standardised instruments to determine illness characteristics at first presentation.

RESULTS

Among the 25 years, and under FEP sample, 23.9% had their first onset of symptoms (prodromal or psychotic) before 18 years of age. After controlling for confounders, the sample aged 25 years and under had a significantly shorter log transformed duration of untreated psychosis (p=0.002), more negative symptoms (p=0.045) and greater frequency of comorbid cannabis abuse diagnosis (p=0.027).

CONCLUSIONS

Symptom onset in a youth FEP sample frequently occurs before age 18 years. Certain illness characteristics differed across the age categories, such as greater negative symptoms and cannabis abuse in the youth sample. Overall, the findings support the provision of adequate strategies for management of negative symptom deficits and substance abuse across all ages in FEP.

The Cannabis Pathway to Non-Affective Psychosis may Reflect Less Neurobiological Vulnerability

There is a high prevalence of cannabis use reported in non-affective psychosis. Early prospective longitudinal studies conclude that cannabis use is a risk factor for psychosis, and neurochemical studies on cannabis have suggested potential mechanisms for this effect. Recent advances in the field of neuroscience and genetics may have important implications for our understanding of this relationship. Importantly, we need to better understand the vulnerability × cannabis interaction to shed light on the mediators of cannabis as a risk factor for psychosis. Thus, the present study reviews recent literature on several variables relevant for understanding the relationship between cannabis and psychosis, including age of onset, cognition, brain functioning, family history, genetics, and neurological soft signs (NSS) in non-affective psychosis. Compared with non-using non-affective psychosis, the present review shows that there seem to be fewer stable cognitive deficits in patients with cannabis use and psychosis, in addition to fewer NSS and possibly more normalized brain functioning, indicating less neurobiological vulnerability for psychosis. There are, however, some familiar and genetic vulnerabilities present in the cannabis psychosis group, which may influence the cannabis pathway to psychosis by increasing sensitivity to cannabis. Furthermore, an earlier age of onset suggests a different pathway to psychosis in the cannabis-using patients. Two alternative vulnerability models are presented to integrate these seemingly paradoxical findings.

Daily use, especially of high-potency cannabis, drives the earlier onset of psychosis in cannabis users

Cannabis use is associated with an earlier age of onset of psychosis (AOP). However, the reasons for this remain debated.

METHODS

We applied a Cox proportional hazards model to 410 first-episode psychosis patients to investigate the association between gender, patterns of cannabis use, and AOP.

RESULTS

Patients with a history of cannabis use presented with their first episode of psychosis at a younger age (mean years = 28.2, SD = 8.0; median years = 27.1) than those who never used cannabis (mean years = 31.4, SD = 9.9; median years = 30.0; hazard ratio [HR] = 1.42; 95% CI: 1.16-1.74; P < .001). This association remained significant after controlling for gender (HR = 1.39; 95% CI: 1.11-1.68; P < .001). Those who had started cannabis at age 15 or younger had an earlier onset of psychosis (mean years = 27.0, SD = 6.2; median years = 26.9) than those who had started after 15 years (mean years = 29.1, SD = 8.5; median years = 27.8; HR = 1.40; 95% CI: 1.06-1.84; P = .050). Importantly, subjects who had been using high-potency cannabis (skunk-type) every day had the earliest onset (mean years = 25.2, SD = 6.3; median years = 24.6) compared to never users among all the groups tested (HR = 1.99; 95% CI: 1.50- 2.65; P < .0001); these daily users of high-potency cannabis had an onset an average of 6 years earlier than that of non-cannabis users.

CONCLUSIONS

Daily use, especially of high-potency cannabis, drives the earlier onset of psychosis in cannabis users.