Mapping and mitigating the health risks of legalizing recreational cannabis use: a call for synergy between research and policy

Risk-thresholds for the association between frequency of cannabis use and the development of psychosis: a systematic review and meta-analysis

BACKGROUND

Epidemiological studies show a dose-response association between cannabis use and the risk of psychosis. This review aimed to determine whether there are identifiable risk-thresholds between the frequency of cannabis use and psychosis development.

METHODS

Systematic search of Embase, MEDLINE, PsycINFO, CINAHL, and Web of Science for relevant studies (1 January 2010-26 April 2021). Case-control or cohort studies that investigated the relationship between cannabis use and the risk of psychosis development that reported effect estimates [odds ratios (OR), hazard ratios (HR), risk ratios (RR)] or the raw data to calculate them, with information on the frequency of cannabis consumption were included. Effect estimates were extracted from individual studies and converted to RR. Two-stage dose-response multivariable meta-analytic models were utilized and sensitivity analyses conducted. The Newcastle Ottawa Scale was used to assess the risk of bias of included studies.

RESULTS

Ten original (three cohorts, seven case-control) studies were included, including 7390 participants with an age range of 12-65 years. Random-effect model meta-analyses showed a significant log-linear dose-response association between cannabis use frequency and psychosis development. A restricted cubic-splines model provided the best fit for the data, with the risk of psychosis significantly increasing for weekly or more frequent cannabis use [RR = 1.01, 95% confidence interval (CI) 0.93-1.11 yearly; RR = 1.10, 95% CI 0.97-1.25 monthly; RR = 1.35, 95% CI 1.19-1.52 weekly; RR = 1.76, 95% CI 1.47-2.12 daily].

CONCLUSION

Individuals using cannabis frequently are at increased risk of psychosis, with no significant risk associated with less frequent use. Public health prevention messages should convey these risk-thresholds, which should be refined through further work.

Schizotypal traits in a large sample of high-school and university students from Tunisia: correlates and measurement invariance of the arabic schizotypal personality questionnaire across age and sex

BACKGROUND

The main goal of the present study was to examine the characteristics of schizotypal traits and their correlations with genetic (i.e., family history of mental illness), demographic (i.e., age, sex), environmental (e.g., income, urbanicity, tobacco/alcohol/cannabis use), and psychological (i.e., personal history of mental illness other than psychosis) factors in Tunisian high-school and university students. Our secondary goal was to contribute the literature by examining the factor structure and factorial invariance of the Arabic Schizotypal Personality Questionnaire (SPQ) across sex and age (adolescents [12-18 years] vs. young adults [18-35 years]) groups.

METHOD

This was a cross-sectional study involving 3166 students: 1160 (36.6%) high-school students (53.0% females, aged 14.9 ± 1.8); and 2006 (63.4%) university students (63.9% females, aged 21.8 ± 2.3). All students were asked to complete a paper-and-pencil self-administered questionnaire containing sociodemographic characteristics as well as the Arabic version of the SPQ.

RESULTS

The total sample yielded total SPQ scores of 24.1 ± 16.6 out of 74. The SPQ yielded good composite reliability as attested by McDonald's omega values ranging from .68 to .80 for all nine subscales. Confirmatory Factor Analysis indicated that fit of the 9-factor model of SPQ scores was acceptable. This model is invariant (at the configural, metric and structural levels) across sex and age. Except for "Odd or eccentric behavior", all schizotypy features were significantly higher among female students compared to males. Multivariable analyses showed that female sex, being a university student, lowest family incomes, tobacco use, and having a personal history of psychiatric illness were significantly associated with higher positive, negative and disorganized schizotypy subscales scores.

CONCLUSION

Future research still needs to confirm our findings and investigate the contribution of the identified factors in the development of clinical psychosis. We can also conclude that the Arabic SPQ is appropriate for measuring and comparing schizotypy across age and sex in clinical and research settings. These findings are highly relevant and essential for ensuring the clinical utility and applicability of the SPQ in cross-cultural research.

Cognitive functioning and cannabis use in first-episode psychosis

AIM

Cannabis use is common in people with psychotic disorders. However, the effect of cannabis on cognition in psychosis remains unclear. Our study investigates relationships between the history of cannabis use and cognitive performance in patients with first-episode psychosis (FEP) during a one-year follow-up.

METHODS

The present study included FEP (N = 91) and control (N = 61) groups. Cannabis use was evaluated with a self-report questionnaire, clinical assessment, and medical records during a lifetime and 12 months prior to the treatment onset (recent). Symptoms of psychosis and anxiety were evaluated on the brief psychiatric rating scale. Negative symptoms were assessed using the scale for the assessment of negative symptoms. Cognitive tests were used to evaluate neurocognition (summarized in the g factor) and social cognition. Crude regression analyses for the g factor included variables of cannabis use as independent variables. Full regression models were controlled for gender, education, and clinical symptoms.

RESULTS

In the FEP group, men used cannabis more frequently than women. In the crude regression model for FEP patients, never having used cannabis was associated with a better neurocognitive profile at 12 months. In the full model, more severe anxiety symptoms were associated with better neurocognition at two months, and less severe negative symptoms were associated with better neurocognition at 12 months. Cannabis use was not associated with social cognition. No associations between cognitive performance and cannabis use emerged in the controls.

CONCLUSION

Negative and affective symptom severity in FEP was associated with cognitive performance to a greater degree than a lifetime history of cannabis use.

Identifying risk-thresholds for the association between frequency of cannabis use and development of cannabis use disorder: A systematic review and meta-analysis

BACKGROUND

Cannabis use disorder (CUD) affects one-in-five cannabis users, presenting a major contributor to cannabis-associated disease burden. Epidemiological data identify the frequency of cannabis use as a risk factor for CUD. This review aimed to determine quantifiable risk-thresholds of the frequency of cannabis use for developing CUD.

METHODS

Systematic search of Medline, EMBASE, PsycInfo, CINAHL, and Web of Science for cohort/case-control studies that assessed the association between frequency of cannabis use and CUD from 2000 to 2022. Effect estimates were converted to risk ratios (RR). A random-effects multi-level multivariate meta-analytic approach was utilized, and sensitivity analyses conducted. Quality of included studies was assessed with the Newcastle Ottawa Scale.

RESULTS

Six prospective cohort studies were included in this review, drawn from two main source studies. Random-effect modeling showed a significant log-linear dose-response association between the frequency of cannabis use and CUD risk (p < 0.0001). The risk of CUD increased from RR:2.03 (95% CI:1.85-2.22) for 'yearly' use, to RR:4.12 (95% CI:3.44-4.95) for 'monthly" use, RR:8.37 (95% CI:6.37-11.00) for 'weekly' use, and RR:16.99 (95% CI:11.80-24.46) for 'daily' use. Multi-level modeling showed an absolute risk increase (ARI) from 3.5% (95% CI:2.6-4.7) for 'yearly' use, to 8.0% (95% CI:5.3-12.1) for 'monthly' use, to 16.8% (95% CI:8.8-32.0) for 'weekly' use, and 36% (95% CI:27.047.9) for 'daily' use.

CONCLUSION

A limited risk of CUD as a potential outcome of cannabis use exists even at infrequent levels of use, but significantly increases as frequency of use increases. Corresponding information should be conveyed to cannabis users as part of targeted prevention messaging to promote safer cannabis use.

The International Cannabis Toolkit (iCannToolkit): a multidisciplinary expert consensus on minimum standards for measuring cannabis use

BACKGROUND

The lack of an agreed international minimum approach to measuring cannabis use hinders the integration of multidisciplinary evidence on the psychosocial, neurocognitive, clinical and public health consequences of cannabis use.

METHODS

A group of 25 international expert cannabis researchers convened to discuss a multidisciplinary framework for minimum standards to measure cannabis use globally in diverse settings.

RESULTS

The expert-based consensus agreed upon a three-layered hierarchical framework. Each layer-universal measures, detailed self-report and biological measures-reflected different research priorities and minimum standards, costs and ease of implementation. Additional work is needed to develop valid and precise assessments.

CONCLUSIONS

Consistent use of the proposed framework across research, public health, clinical practice and medical settings would facilitate harmonisation of international evidence on cannabis consumption, related harms and approaches to their mitigation.

Youth Cannabis use and Legalization in Canada - Reconsidering the Fears, Myths and Facts Three Years In

Canada legalized and regulated non-medical cannabis in October 2018, and in the lead up to this policy change much debate was generated around the Federal Government's stated objective of "keeping cannabis out of the hands of children and youth". As Canada moved through the process of passing Bill C-45 (the Cannabis Act), a contentious issue was whether the 'public health approach' to legalization with strict regulation guiding Federal policy would protect young people from accessing cannabis and from the potential harms of use. Now that we are several years post-legalization of cannabis, in this brief commentary we reconsider the arguments made about the potential consequences of legalization for youth, centered on three key concerns: that prevalence would significantly increase, that there would be greater incidence of harms to youth brain development, and that there would be increased presentations of severe mental illnesses associated with cannabis use. We also consider how focusing narrowly on clinical outcomes has neglected the association between criminalization and social inequities, where the burdens are disproportionate for marginalized and racialized youth.

Efficacy and safety of COVID-19 vaccines: a systematic review

OBJECTIVE

To evaluate systematically the efficacy and safety of COVID-19 vaccines.

METHODS

PubMed, Embase, Cochrane Library, Clinicaltrial.gov, CNKI, Wanfang Data, China Biomedical Literature Service System, and China Clinical Trial Registry were searched for randomized controlled trials of COVID-19 vaccines published up to December 31, 2020. The Cochrane bias risk assessment tool was used to assess the quality of studies. A qualitative analysis was performed on the results of clinical trials.

RESULTS

Thirteen randomized, blinded, controlled trials, which involved the safety and efficacy of 11 COVID-19 vaccines, were included. In 10 studies, the 28-day seroconversion rate of subjects exceeded 80%. In two 10 000-scale clinical trials, the vaccines were effective in 95% and 70.4% of the subjects, respectively. The seroconversion rate was lower than 60% in only one study. In six studies, the proportion of subjects who had an adverse reaction within 28 days after vaccination was lower than 30%. This proportion was 30%-50% in two studies and > 50% in the other two studies. Most of the adverse reactions were mild to moderate and resolved within 24 hours after vaccination. The most common local adverse reaction was pain or tenderness at the injection site, and the most common systemic adverse reaction was fatigue, fever, or bodily pain. The immune response and incidence of adverse reactions to the vaccines were positively correlated with the dose given to the subjects. The immune response to the vaccines was worse in the elderly than in the younger population. In 6 studies that compared single-dose and double-dose vaccination, 4 studies showed that double-dose vaccination produced a stronger immune response than single-dose vaccination.

CONCLUSIONS

Most of the COVID-19 vaccines appear to be effective and safe. Double-dose vaccination is recommended. However, more research is needed to investigate the long-term efficacy and safety of the vaccines and the influence of dose, age, and production process on the protective efficacy.