Cannabis use and transition to psychosis in individuals at ultra-high risk: review and meta-analysis

What Causes the Onset of Psychosis in Individuals at Clinical High Risk? A Meta-analysis of Risk and Protective Factors

Twenty percent of individuals at clinical high risk for psychosis (CHR-P) develop the disorder within 2 years. Extensive research has explored the factors that differentiate those who develop psychosis and those who do not, but the results are conflicting. The current systematic review and meta-analysis comprehensively addresses the consistency and magnitude of evidence for non-purely genetic risk and protective factors associated with the risk of developing psychosis in CHR-P individuals. Random effects meta-analyses, standardized mean difference (SMD) and odds ratio (OR) were used, in combination with an established stratification of evidence that assesses the association of each factor and the onset of psychotic disorders (from class I, convincing evidence to class IV weak evidence), while controlling for several types of biases. A total of 128 original controlled studies relating to 26 factors were retrieved. No factors showed class I-convincing evidence. Two further factors were associated with class II-highly suggestive evidence: attenuated positive psychotic symptoms (SMD = 0.348, 95% CI: 0.280, 0.415) and global functioning (SMD = -0.291, 95% CI: -0.370, -0.211). There was class III-suggestive evidence for negative psychotic symptoms (SMD = 0.393, 95% CI: 0.317, 0.469). There was either class IV-weak or no evidence for all other factors. Our findings suggest that despite the large number of putative risk factors investigated in the literature, only attenuated positive psychotic symptoms, global functioning, and negative psychotic symptoms show suggestive evidence or greater for association with transition to psychosis. The current findings may inform the refinement of clinical prediction models and precision medicine in this field.

Migrant status and identification as ultra-high risk for psychosis and transitioning to a psychotic disorder

BACKGROUND

Certain migrant groups are more likely to develop a psychotic disorder compared to the native-born populations, and a younger age at migration is associated with greater risk. However, it is not known at which stage migration has an effect on the development of psychotic disorders. We examined whether migrants were more likely to be identified as ultra-high risk for psychosis (UHR) compared to native-born young people and whether migrant status was associated with the risk of transition to a full-threshold psychotic disorder.

METHODS

The cohort included all young people aged 15-24 who were identified as UHR at a specialist clinic over a five-year period (2012-16). Australian census data were used to obtain the at-risk population. Poisson regression was used to calculate rate ratios and Cox regression analysis determined hazard ratios.

RESULTS

467 young people were identified as UHR, of which 13.5% (n = 63) were born overseas. First-generation migrants were 2.6-fold less likely to be identified as UHR compared to Australian-born young people (IRR = 0.39, 95% CI [0.30, 0.51], P < 0.001). There was no difference between migrant and native-born young people in their risk of transitioning to a psychotic disorder (HR = 0.90, 95% CI [0.39, 2.08], P = 0.81).

CONCLUSIONS

UHR first-generation migrants may be under-accessing mental health services.

Cannabis Use and the Risk for Psychosis and Affective Disorders

Objective: This review discusses the relationship between cannabis use and psychotic, bipolar, depressive, and anxiety disorders, as well as suicide. It summarizes epidemiological evidence from cross-sectional and long-term prospective studies and considers possible etiological mechanisms. Methods: Systematic reviews and methodologically robust studies in the field (from inception to February 2019) were identified using a comprehensive search of Medline, PsychINFO, and Embase and summarized using a narrative synthesis. Results: Consistent evidence, both from observational and experimental studies, has confirmed the important role of cannabis use in the initiation and persistence of psychotic disorders. The size of the effect is related to the extent of cannabis use, with greater risk for early cannabis use and use of high-potency varieties and synthetic cannabinoids. Accumulating evidence suggests that frequent cannabis use also increases the risk for mania as well as for suicide. However, the effect on depression is less clear and findings on anxiety are contradictory with only a few methodologically robust studies. Furthermore, the relationship with common mental disorders may involve reverse causality, as depression and anxiety are reported to lead to greater cannabis consumption in some studies. Pathogenetic mechanisms focus on the effect of tetrahydrocannabinol (THC, the main psychoactive ingredient of cannabis) interacting with genetic predisposition and perhaps other environmental risk factors. Cannabidiol (CBD), the other important ingredient of traditional cannabis, ameliorates the psychotogenic effects of THC but is absent from the high-potency varieties that are increasingly available. Conclusions: The evidence that heavy use of high-THC/low-CBD types of cannabis increases the risk of psychosis is sufficiently strong to merit public health education. Evidence of similar but smaller effects in mania and suicide is growing, but is not convincing for depression and anxiety. There is much current interest in the possibility that CBD may be therapeutically useful.

Adverse Effects of Cannabis Use on Neurocognitive Functioning: A Systematic Review of Meta- Analytic Studies

Objective: As the perceived risk of cannabis use continues to decline among youths and access continues to increase, it has become more important to synthesize the rapidly growing literature on the effects of cannabis on neurocognition. Hundreds of studies examining associations between cannabis use and neurocognitive functioning have been published in recent decades. However, results often differ across individual studies, particularly when sample sizes are small. Meta-analytic methods help to make sense of this literature and have been increasingly applied to studies on cannabis use and neurocognition. Methods: A systematic literature search using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted to identify peer-reviewed meta-analyses of neurocognitive or functional neuroimaging data that examined associations between cannabis use and non-acute effects on neurocognitive functioning (n = 8). Results: Current findings suggest that regular healthy cannabis users, regardless of age, display poorer neurocognitive functioning relative to nonusers of small to medium effect sizes across many neurocognitive domains, as well as functional brain alterations when compared to non-users. Adverse effects are not uniform across neurocognitive domains and evidence for adolescent-onset users having poorer neurocognitive outcomes remains equivocal based on these studies. However, less is known about cannabis effects on neurocognition among clinical samples, as findings from specific clinical samples revealed mixed results. Conclusions: Meta-analyses have played an important role in helping to grasp the totality of results from a large body of literature on cannabis effects on neurocognition, yet more research (particularly large-scale longitudinal studies) is needed to identify critical periods or patterns of use that are more likely to result in negative outcomes.

The "Reggio Emilia At-Risk Mental States" program: A diffused, "liquid" model of early intervention in psychosis implemented in an Italian Department of Mental Health

AIM

From September 2012, the Reggio Emilia Department of Mental Health developed a specific program (the "Reggio Emilia At-Risk Mental States" [ReARMS] protocol) as a diffused, "liquid" infrastructure for early intervention in psychosis. Aims of the current study are (a) to describe the ReARMS macroscopic organization and (b) to examine specific process indicators during the first 5 years of clinical activity.

METHODS

All participants (n = 300) were young help-seekers, aged 13 to 35 years, who completed the Comprehensive Assessment of At-Risk Mental States (CAARMS).

RESULTS

At baseline, 95 (31.7%) participants did not meet CAARMS-defined criteria, while 205 (68.3%) were offered a dedicated protocol of care: 154 (75.1%) of them were enrolled in the program, 19 (9.3%) refused and 32 (15.6%) dropped out during the first year of treatment. Individuals enrolled in the ReARMS protocol were mainly referred by general practitioners (33.3%), emergency room/general hospital (24%) or they were self-referred (15%). In comparison with ultra-high risk individuals, patients with first episode psychosis showed significantly higher mean age at entry and preponderance of males, as well as higher percentages of history of substance abuse and previous hospitalization.

CONCLUSIONS

An early intervention in psychosis service in Italian child/adolescent and adult mental health services are feasible and clinically relevant, also in adolescents, who have a high risk of falling through the child-adult service gap as they cross the transition boundary between services.

Estimating Exposome Score for Schizophrenia Using Predictive Modeling Approach in Two Independent Samples: The Results From the EUGEI Study

Exposures constitute a dense network of the environment: exposome. Here, we argue for embracing the exposome paradigm to investigate the sum of nongenetic "risk" and show how predictive modeling approaches can be used to construct an exposome score (ES; an aggregated score of exposures) for schizophrenia. The training dataset consisted of patients with schizophrenia and controls, whereas the independent validation dataset consisted of patients, their unaffected siblings, and controls. Binary exposures were cannabis use, hearing impairment, winter birth, bullying, and emotional, physical, and sexual abuse along with physical and emotional neglect. We applied logistic regression (LR), Gaussian Naive Bayes (GNB), the least absolute shrinkage and selection operator (LASSO), and Ridge penalized classification models to the training dataset. ESs, the sum of weighted exposures based on coefficients from each model, were calculated in the validation dataset. In addition, we estimated ES based on meta-analyses and a simple sum score of exposures. Accuracy, sensitivity, specificity, area under the receiver operating characteristic, and Nagelkerke's R2 were compared. The ESMeta-analyses performed the worst, whereas the sum score and the ESGNB were worse than the ESLR that performed similar to the ESLASSO and ESRIDGE. The ESLR distinguished patients from controls (odds ratio [OR] = 1.94, P < .001), patients from siblings (OR = 1.58, P < .001), and siblings from controls (OR = 1.21, P = .001). An increase in ESLR was associated with a gradient increase of schizophrenia risk. In reference to the remaining fractions, the ESLR at top 30%, 20%, and 10% of the control distribution yielded ORs of 3.72, 3.74, and 4.77, respectively. Our findings demonstrate that predictive modeling approaches can be harnessed to evaluate the exposome.

The psychosis risk timeline: can we improve our preventive strategies? Part 2: adolescence and adulthood

Current understanding of psychosis development is relevant to patients' clinical outcomes in mental health services as a whole, given that psychotic symptoms can be a feature of many different diagnoses at different stages of life. Understanding the risk factors helps clinicians to contemplate primary, secondary and tertiary preventive strategies that it may be possible to implement. In this second article of a three-part series, the psychosis risk timeline is again considered, here focusing on risk factors more likely to be encountered during later childhood, adolescence and adulthood. These include environmental factors, substance misuse, and social and psychopathological aspects.

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DECLARATION OF INTEREST:

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Predictors of Transition to Psychosis in Individuals at Clinical High Risk

PURPOSE OF REVIEW

Current research is examining predictors of the transition to psychosis in youth who are at clinical high risk based on attenuated psychotic symptoms (APS). Determining predictors of the development of psychosis is important for an improved understanding of mechanisms as well as the development of preventative strategies. The purpose is to review the most recent literature identifying predictors of the transition to psychosis in those who are already assessed as being at risk.

RECENT FINDINGS

Multidomain models, in particular, integrated models of symptoms, social functioning, and cognition variables, achieve better predictive performance than individual factors. There are many methodological issues; however, several solutions have now been described in the literature. For youth who already have APS, predicting who may go on to later develop psychosis is possible. Several studies are underway in large consortiums that may overcome some of the methodological concerns and develop improved means of prediction.

Federated multi-site longitudinal study of at-risk mental state for psychosis in Japan

There has been recent accumulation of evidence and clinical guidance regarding the at-risk mental state (ARMS) for psychosis. However, most studies have been observational cohort and intervention studies of Western populations. To assess the validity of the ARMS concept and the transition rate to psychosis in a non-Western nation, we retrospectively combined and analyzed clinical data of individuals diagnosed with ARMS who were prospectively followed-up at three specialized clinical services for ARMS in Japan. In total, we included 309 individuals with ARMS, of whom 43 developed overt psychosis. We estimated cumulative transition rates to psychosis with the Kaplan-Meier method, obtaining rates of 12% at 12, 16% at 24, 19% at 36, and 20% at 48 months. Only two individuals reported past cannabis use. Despite several differences among the three sites, transition rates did not differ among them. Furthermore, the transition rate of children aged between 14 and 17 years did not differ from that of individuals aged 18 years or older. Regression analysis revealed that meeting the brief limited intermittent psychotic symptoms (BLIPS) criterion was associated with an increased risk of transition to psychosis, whereas genetic risk factors were not. Although antipsychotic prescription was relatively frequent in this cohort, there was no evidence supporting frequent use of antipsychotics for this population. In conclusion, our findings support the assertion that the current concept of ARMS is applicable in Japan. Development of local clinical guidelines and training for clinicians is necessary to disseminate this concept to more clinical settings.

Impact of rurality and substance use on young people at ultra high risk for psychosis

BACKGROUND

Longitudinal research into early intervention for youth at ultra high risk (UHR) for psychosis demonstrates beneficial outcomes including increased treatment compliance and greater participation in education and the workforce. Despite known barriers for rural youth accessing mental health services, research comparing urban and rural UHR youth is lacking. The study included an examination of the impact of substance use on functioning of UHR youth.

METHODS

Youth aged 12 to 25 years were recruited from the urban area of Newcastle or the rural area of Orange, New South Wales, Australia, and identified as UHR by the Comprehensive Assessment of At Risk Mental States. Rural and urban youth were compared on clinical profiles, social and occupational functioning and substance use.

RESULTS

The rural youth showed different help-seeking behaviours and had greater functional impairment than urban youth. Substance use was common across the sample of 57 youth (mean age 16.5 years, 56% female) and a history of hazardous substance use was associated with higher levels of depression. Rural youth (n = 32) were more likely than urban youth to be taking antidepressants at baseline (44% compared with 16%).

CONCLUSION

Different patterns of help seeking by rural UHR youth suggest a need for greater access to psychosis informed primary care early intervention services. Interventions should target functional decline to prevent adverse outcomes such as reduced community participation and unemployment. In addition, interventions for substance use should be a priority for UHR youth, who should also be screened and monitored for depressive symptoms and treated for depression if indicated.

Social network confidants, duration of untreated psychosis and cannabis use in people with first episode psychosis: An exploratory study

AIM

Reduced social network (SN) might be associated with a longer duration of untreated psychosis (DUP) in people with first episode psychosis (FEP). We aimed at exploring the specific role of SN confidants on DUP, taking into account cannabis misuse, which is known to influence DUP and might be associated with social functioning.

METHODS

People with FEP recently referred to an inner London Early Intervention Service were assessed with standardized instruments exploring SN characteristics, DUP and cannabis misuse.

RESULTS

Taking into account cannabis misuse, we found an association between confidants and DUP (P = 0.020), with the higher the number of confidants, the shorter the DUP.

CONCLUSIONS

Confidants may provide access to, and perceptions of, social support and this may increase early engagement for people with FEP, reducing DUP and possibly improving outcomes. Future research should identify correlates of small networks of confidants, which could inform early detection community initiatives.

The adverse health effects and harms related to marijuana use: an overview review

BACKGROUND

With impending marijuana legislation in Canada, a broad understanding of the harms associated with marijuana use is needed to inform the clinical community and public, and to support evidence-informed public policy development. The purpose of the review was to synthesize the evidence on adverse health effects and harms of marijuana use.

METHODS

We searched MEDLINE, The Cochrane Database of Systematic Reviews, Embase, PsycINFO, the Cumulative Index to Nursing and Allied Health Literature, and the Health Technology Assessment Database from the inception of each database to May 2018. Given that systematic reviews evaluating one or other specific harm have been published, this is an overview review with the primary objective of assessing a health effect or harm. Data on author, country and year of publication, search strategy and results, and outcomes were extracted. Quality was assessed using the AMSTAR (A Measurement Tool to Assess Systematic Reviews) checklist.

RESULTS

The final analysis included 68 reviews. Evidence of harm was reported in 62 reviews for several mental health disorders, brain changes, cognitive outcomes, pregnancy outcomes and testicular cancer. Inconclusive evidence was found for 20 outcomes (some mental health outcomes, other types of cancers and all-cause mortality). No evidence of harm was reported for 6 outcomes.

INTERPRETATION

Harm was associated with most outcomes assessed. These results should be viewed with concern by physicians and policy-makers given the prevalence of use, the persistent reporting of a lack of recognition of marijuana as a possibly harmful substance and the emerging context of legalization for recreational use.

Associations between adolescent cannabis use and brain structure in psychosis

Associations between cannabis use and psychotic disorders suggest that cannabis may be a contributory risk factor in the neurobiology of psychosis. In this study, we examined brain structure characteristics, total and regional gray matter density (GMD), using Voxel Based Morphometry, in psychotic individuals, stratified by history of cannabis use (total n = 109). We also contrasted GMD estimates in individual diagnostic groups (schizophrenia/bipolar I disorder) with and without history of adolescent cannabis use (ACU). Individuals with psychosis as a whole, both with and without history of ACU, had lower total and regional GMD, compared to healthy controls. ACU was associated with attenuated GMD reductions, compared to non-users, especially in the schizophrenia cases, who showed robust GMD reductions in fronto-temporal and parietal cortex, as well as subcortical regions. Notably, total and regional GMD estimates in individuals with psychosis and ACU were not different from controls with no ACU. These data indicate that the history of ACU in psychotic individuals is associated with attenuated GMD abnormalities. Future investigations targeting potential unique etiological and risk factors associated with psychosis in individuals with ACU may help in understanding of the neurobiology of psychotic disorders and novel treatment options for these individuals.

Medical marijuana laws and adolescent marijuana use in the United States: a systematic review and meta-analysis

AIMS

To conduct a systematic review and meta-analysis of studies in order to estimate the effect of US medical marijuana laws (MMLs) on past-month marijuana use prevalence among adolescents.

METHODS

A total of 2999 papers from 17 literature sources were screened systematically. Eleven studies, developed from four ongoing large national surveys, were meta-analyzed. Estimates of MML effects on any past-month marijuana use prevalence from included studies were obtained from comparisons of pre-post MML changes in MML states to changes in non-MML states over comparable time-periods. These estimates were standardized and entered into a meta-analysis model with fixed-effects for each study. Heterogeneity among the study estimates by national data survey was tested with an omnibus F-test. Estimates of effects on additional marijuana outcomes, of MML provisions (e.g. dispensaries) and among demographic subgroups were abstracted and summarized. Key methodological and modeling characteristics were also described. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed.

RESULTS

None of the 11 studies found significant estimates of pre-post MML changes compared with contemporaneous changes in non-MML states for marijuana use prevalence among adolescents. The meta-analysis yielded a non-significant pooled estimate (standardized mean difference) of -0.003 (95% confidence interval = -0.012, +0.007). Four studies compared MML with non-MML states on pre-MML differences and all found higher rates of past-month marijuana use in MML states pre-MML passage. Additional tests of specific MML provisions, of MML effects on additional marijuana outcomes and among subgroups generally yielded non-significant results, although limited heterogeneity may warrant further study.

CONCLUSIONS

Synthesis of the current evidence does not support the hypothesis that US medical marijuana laws (MMLs) until 2014 have led to increases in adolescent marijuana use prevalence. Limited heterogeneity exists among estimates of effects of MMLs on other patterns of marijuana use, of effects within particular population subgroups and of effects of specific MML provisions.

US Epidemiology of Cannabis Use and Associated Problems

This review provides an overview of the changing US epidemiology of cannabis use and associated problems. Adults and adolescents increasingly view cannabis as harmless, and some can use cannabis without harm. However, potential problems include harms from prenatal exposure and unintentional childhood exposure; decline in educational or occupational functioning after early adolescent use, and in adulthood, impaired driving and vehicle crashes; cannabis use disorders (CUD), cannabis withdrawal, and psychiatric comorbidity. Evidence suggests national increases in cannabis potency, prenatal and unintentional childhood exposure; and in adults, increased use, CUD, cannabis-related emergency room visits, and fatal vehicle crashes. Twenty-nine states have medical marijuana laws (MMLs) and of these, 8 have recreational marijuana laws (RMLs). Many studies indicate that MMLs or their specific provisions did not increase adolescent cannabis use. However, the more limited literature suggests that MMLs have led to increased cannabis potency, unintentional childhood exposures, adult cannabis use, and adult CUD. Ecological-level studies suggest that MMLs have led to substitution of cannabis for opioids, and also possibly for psychiatric medications. Much remains to be determined about cannabis trends and the role of MMLs and RMLs in these trends. The public, health professionals, and policy makers would benefit from education about the risks of cannabis use, the increases in such risks, and the role of marijuana laws in these increases.

Comorbid diagnoses for youth at clinical high risk of psychosis

Several studies have demonstrated that youth at clinical high risk (CHR) of developing psychosis have a high prevalence of comorbid psychiatric disorders. Less is known about the impact of comorbid diagnoses on later conversion to psychosis and the change over time. The aim of this study was to determine the frequency and distribution of psychiatric diagnoses at baseline and over time in the North American Prodrome Longitudinal Study (NAPLS 2) and the role of comorbid diagnoses in conversion to psychosis. The NAPLS 2 sample consisted of 744 CHR youth and 276 healthy controls. Only 21% of the CHR group did not have a comorbid diagnosis with many have 2-3 DSM-IV comorbid diagnoses. The most common diagnoses were anxiety and depressive disorders, which did improve over time. The only diagnosis at baseline that differentiated the converters from the non-converters was cannabis misuse. Comorbidity, except for cannabis use, was essentially independent of clinical outcome. It is possible that those with comorbid diagnoses are preferentially the help-seeking individuals that present for help in our clinics and research projects and that those who are at risk but do not have a comorbid diagnosis may not be seeking help in the prodromal phase.

Demographic, physical and mental health assessments in the adolescent brain and cognitive development study: Rationale and description

The Adolescent Brain and Cognitive Development (ABCD) Study incorporates a comprehensive range of measures assessing predictors and outcomes related to both mental and physical health across childhood and adolescence. The workgroup developed a battery that would assess a comprehensive range of domains that address study aims while minimizing participant and family burden. We review the major considerations that went into deciding what constructs to cover in the demographics, physical health and mental health domains, as well as the process of selecting measures, piloting and refining the originally proposed battery. We present a description of the baseline battery, as well as the six-month interim assessments and the one-year follow-up assessments. This battery includes assessments from the perspectives of both the parent and the target youth, as well as teacher reports. This battery will provide a foundational baseline assessment of the youth's current function so as to permit characterization of stability and change in key domains over time. The findings from this battery will also be utilized to identify both resilience markers that predict healthy development and risk factors for later adverse outcomes in physical health, mental health, and substance use and abuse.

Predicting Persistent, Limited, and Delayed Problematic Cannabis Use in Early Adulthood: Findings From a Longitudinal Study

OBJECTIVE

To identify risk profiles associated with patterns of problematic cannabis use in early adulthood.

METHOD

Data came from 1,229 participants in the Great Smoky Mountains Study, a prospective 20-year cohort study from 1993 to 2015 that is representative of western North Carolina with yearly assessments conducted from ages 9 and 16 years, and assessments at ages 19, 21, 26, and 30 years. Patterns of problematic cannabis use (i.e., DSM-5 cannabis use disorder or daily use) in early adulthood included the following: nonproblematic use in late adolescence (ages 19-21) and early adulthood (ages 26-30); limited problematic use in late adolescence only; persistent problematic use in late adolescence and early adulthood; and delayed problematic use in early adulthood only. Multinominal logistic regression models examined pairwise associations between these patterns and risk factors in childhood/early adolescence (ages 9-16) and late adolescence (ages 19-21). Risk factors included psychiatric disorders (e.g., anxiety, depressive), other substance use (smoking, alcohol, illicit drugs), and challenging social factors (e.g., low socioeconomic status, family functioning, peers). Sex and race/ethnicity (white, African American, American Indian) interactions were tested.

RESULTS

The persistent pattern (6.7% of sample) was characterized by more anxiety disorders across development and more DSM-5 CUD symptoms during late adolescence compared to the limited pattern (13.3%), which, in turn, had more childhood family instability and dysfunction. The delayed pattern (3.7%) was characterized by more externalizing disorders, maltreatment, and peer bullying in childhood compared to those in nonproblematic users. There were no significant interactions of sex or race/ethnicity.

CONCLUSION

Problematic cannabis use patterns during early adulthood have distinctive risk profiles, which may be useful in tailoring targeted interventions.

The relationship between cannabis use and cortisol levels in youth at ultra high-risk for psychosis

Recent studies have posited a relationship between cannabis use and the biological stress system, but this critical relationship has not been evaluated during the ultra high-risk (UHR) period immediately preceding the onset of psychotic disorders. Salivary cortisol samples were collected on 46 UHR and 29 control adolescents; these individuals were assessed for current cannabis use with a urine panel and self-report. UHR participants where separated into two groups: Current Cannabis Use (UHR-CU) and No Current Cannabis Use (UHR-NC). Healthy Control participants (HC) were free of cannabis use. Consistent with the literature, results indicate UHR individuals showed elevated cortisol levels when compared to HC participants. Further, we also observed that UHR-CU participants exhibited elevated levels when compared to both the non-using UHR and HC groups. Findings suggest that cannabis use may interact with underlying biological vulnerability associated with the hypothalamic-pituitary-adrenal (HPA) axis system.

Lower-Risk Cannabis Use Guidelines: A Comprehensive Update of Evidence and Recommendations

BACKGROUND

Cannabis use is common in North America, especially among young people, and is associated with a risk of various acute and chronic adverse health outcomes. Cannabis control regimes are evolving, for example toward a national legalization policy in Canada, with the aim to improve public health, and thus require evidence-based interventions. As cannabis-related health outcomes may be influenced by behaviors that are modifiable by the user, evidence-based Lower-Risk Cannabis Use Guidelines (LRCUG)-akin to similar guidelines in other health fields-offer a valuable, targeted prevention tool to improve public health outcomes.

OBJECTIVES

To systematically review, update, and quality-grade evidence on behavioral factors determining adverse health outcomes from cannabis that may be modifiable by the user, and translate this evidence into revised LRCUG as a public health intervention tool based on an expert consensus process.

SEARCH METHODS

We used pertinent medical search terms and structured search strategies, to search MEDLINE, EMBASE, PsycINFO, Cochrane Library databases, and reference lists primarily for systematic reviews and meta-analyses, and additional evidence on modifiable risk factors for adverse health outcomes from cannabis use.

SELECTION CRITERIA

We included studies if they focused on potentially modifiable behavior-based factors for risks or harms for health from cannabis use, and excluded studies if cannabis use was assessed for therapeutic purposes.

DATA COLLECTION AND ANALYSIS

We screened the titles and abstracts of all studies identified by the search strategy and assessed the full texts of all potentially eligible studies for inclusion; 2 of the authors independently extracted the data of all studies included in this review. We created Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow-charts for each of the topical searches. Subsequently, we summarized the evidence by behavioral factor topic, quality-graded it by following standard (Grading of Recommendations Assessment, Development, and Evaluation; GRADE) criteria, and translated it into the LRCUG recommendations by the author expert collective on the basis of an iterative consensus process.

MAIN RESULTS

For most recommendations, there was at least "substantial" (i.e., good-quality) evidence. We developed 10 major recommendations for lower-risk use: (1) the most effective way to avoid cannabis use-related health risks is abstinence, (2) avoid early age initiation of cannabis use (i.e., definitively before the age of 16 years), (3) choose low-potency tetrahydrocannabinol (THC) or balanced THC-to-cannabidiol (CBD)-ratio cannabis products, (4) abstain from using synthetic cannabinoids, (5) avoid combusted cannabis inhalation and give preference to nonsmoking use methods, (6) avoid deep or other risky inhalation practices, (7) avoid high-frequency (e.g., daily or near-daily) cannabis use, (8) abstain from cannabis-impaired driving, (9) populations at higher risk for cannabis use-related health problems should avoid use altogether, and (10) avoid combining previously mentioned risk behaviors (e.g., early initiation and high-frequency use).

AUTHORS' CONCLUSIONS

Evidence indicates that a substantial extent of the risk of adverse health outcomes from cannabis use may be reduced by informed behavioral choices among users. The evidence-based LRCUG serve as a population-level education and intervention tool to inform such user choices toward improved public health outcomes. However, the LRCUG ought to be systematically communicated and supported by key regulation measures (e.g., cannabis product labeling, content regulation) to be effective. All of these measures are concretely possible under emerging legalization regimes, and should be actively implemented by regulatory authorities. The population-level impact of the LRCUG toward reducing cannabis use-related health risks should be evaluated. Public health implications. Cannabis control regimes are evolving, including legalization in North America, with uncertain impacts on public health. Evidence-based LRCUG offer a potentially valuable population-level tool to reduce the risk of adverse health outcomes from cannabis use among (especially young) users in legalization contexts, and hence to contribute to improved public health outcomes.

Cannabis use and symptom severity in individuals at ultra high risk for psychosis: a meta-analysis

OBJECTIVE

We aimed to assess whether individuals at ultra high risk (UHR) for psychosis have higher rates of cannabis use and cannabis use disorders (CUDs) than non-UHR individuals and determine whether UHR cannabis users have more severe psychotic experiences than non-users.

METHOD

We conducted a meta-analysis of studies reporting cannabis use in the UHR group and/or positive or negative symptoms among UHR cannabis users and non-users. Logit event rates were calculated for cannabis use, in addition to odds ratios to assess the difference between UHR and controls. Severity of clinical symptoms in UHR cannabis users and non-users was compared using Hedges' g.

RESULTS

Thirty unique studies were included (UHR n = 4205, controls n = 667) containing data from cross-sectional and longitudinal studies, and randomised control trials. UHR individuals have high rates of current (26.7%) and lifetime (52.8%) cannabis use, and CUDs (12.8%). Lifetime use and CUDs were significantly higher than controls (lifetime OR: 2.09; CUD OR: 5.49). UHR cannabis users had higher rates of unusual thought content and suspiciousness than non-users.

CONCLUSION

Ultra high risk individuals have high rates of cannabis use and CUDs, and cannabis users had more severe positive symptoms. Targeting substance use during the UHR phase may have significant benefits to an individual's long-term outcome.

Prediction of conversion to psychosis in individuals with an at-risk mental state: a brief update on recent developments

PURPOSE OF REVIEW

So far, only little more than one-third of individuals classified as being at-risk for psychosis have been shown to actually convert to frank psychosis during follow-up. There have therefore been enormous efforts to improve the accuracy of predicting this transition. We reviewed the most recent studies in the field with the aim to clarify whether accuracy of prediction has been improved by the different research endeavors and what could be done to further improve it, and/or what alternative goals research should pursue.

RECENT FINDINGS

A total of 56 studies published between May 2015 and December 2016 were included, of which eight were meta-analyses. New meta-analytical evidence confirms that established instruments for checking clinical risk criteria have an excellent clinical utility in individuals referred to high-risk services. Within a such identified group of ultra-high-risk (UHR) individuals, especially Brief Limited Intermittent Psychotic Symptoms and Attenuated Psychotic Symptoms seem to predict transition. Further assessments should be performed within the UHR individuals, as risk of transition seems particularly high in those with an even higher severity of certain symptoms such as suspiciousness or anhedonia, in those with lower global or social functioning, poor neurocognitive performance or cannabis abuse. Also, electroencephalography, neuroimaging and blood biomarkers might contribute to improving individual prediction. The most promising approach certainly is a staged multidomain assessment. Risk calculators to integrate all data for an individualized prediction are being developed.

SUMMARY

Prediction of psychosis is already possible with an excellent prognostic performance based on clinical assessments. Recent studies show that this accuracy can be further improved by using multidomain approaches and modern statistics for individualized prediction. The challenge now is the translation into the clinic with a broad clinical implementation.

The "polyenviromic risk score": Aggregating environmental risk factors predicts conversion to psychosis in familial high-risk subjects

BACKGROUND

Young relatives of individuals with schizophrenia (i.e. youth at familial high-risk, FHR) are at increased risk of developing psychotic disorders, and show higher rates of psychiatric symptoms, cognitive and neurobiological abnormalities than non-relatives. It is not known whether overall exposure to environmental risk factors increases risk of conversion to psychosis in FHR subjects.

METHODS

Subjects consisted of a pilot longitudinal sample of 83 young FHR subjects. As a proof of principle, we examined whether an aggregate score of exposure to environmental risk factors, which we term a 'polyenviromic risk score' (PERS), could predict conversion to psychosis. The PERS combines known environmental risk factors including cannabis use, urbanicity, season of birth, paternal age, obstetric and perinatal complications, and various types of childhood adversity, each weighted by its odds ratio for association with psychosis in the literature.

RESULTS

A higher PERS was significantly associated with conversion to psychosis in young, familial high-risk subjects (OR=1.97, p=0.009). A model combining the PERS and clinical predictors had a sensitivity of 27% and specificity of 96%.

CONCLUSION

An aggregate index of environmental risk may help predict conversion to psychosis in FHR subjects.

Evidence-based Treatment Options in Cannabis Dependency

BACKGROUND

Now that the consumption of natural and synthetic cannabinoids is becoming more widespread, the specific treatment of cannabis-related disturbances is an increasingly important matter. There are many therapeutic options, and it is not always clear which ones are evidence-based and appropriate for use in a given clinical situation.

METHODS

This review is based on reports of pertinent randomized and controlled trials (RCTs) that were retrieved by a selective search in the PubMed and Cochrane databases.

RESULTS

Cognitive behavior therapy (CBT) combined with other techniques has been found to have a moderate to large effect (Cohen's d = 0.53-0.9) on the amount of cannabis consumed as well as on the level of psychosocial functioning or the dependence syndrome. Systemic multidimensional family therapy (MDFT) has been found beneficial for younger adolescents who consume large amounts of cannabis and have psychiatric comorbidities. Short-term interventions with motivational talk therapy have been found effective for patients with or without an initial desire to achieve cannabis abstinence. All of these psychotherapeutic interventions are effective at evidence level Ia. The administration of gabapentin had a weak effect (d = 0.26) on the quantity consumed and on abstinence (evidence level Ib). Withdrawal symptoms can be alleviated with cannabinoid-receptor antagonists (d = 0.223 and 0.481) (evidence level Ib). On the other hand, there is evidence that serotonergic antidepressants can worsen withdrawal manifestations and increase the likelihood of relapse.

CONCLUSION

Psychotherapeutic techniques remain the foundation of treatment for cannabis dependence. No drug has yet been approved for the treatment of cannabis dependence because of the lack of scientific evidence. The rates of abstinence that are currently achieved, even with psychotherapy, are still only moderate. Further clinical studies are needed for the evaluation of combinations of various treatments that can meet the needs of individual patients.

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.