There is a substantial body of literature on environmental risk associated with schizophrenia. Most research has largely been conducted in Europe and North America, with little representation of the rest of the world; hence generalisability of findings is questionable. For this reason, we performed a mapping review of studies on environmental risk for schizophrenia spectrum disorders, recording the country where they were conducted, and we linked our findings with publicly available data to identify correlates with the uneven global distribution. Our aim was to evaluate how universal is the ‘common knowledge’ of environmental risk for psychosis collating the availability of evidence across different countries and to generate suggestions for future research identifying gaps in evidence.

We performed a systematic search and mapping of studies in the PubMed and PsycINFO electronic databases reporting on exposure to environmental risk for schizophrenia including obstetric complications, paternal age, migration, urbanicity, childhood trauma, and cannabis use and subsequent onset of schizophrenia spectrum disorders. This search focused on articles published from the date of the first available publication until 31 May 2023. We recorded the country where they were conducted. We downloaded publicly available data on population size, measures of wealth, medical provisions, research investment, and of quality research outputs per country and performed regression analyses of each predictor with the number of studies and recruited cases in each country.

We identified 308 publications that included a sample size of 445,000 patients with schizophrenia spectrum disorders. The majority were conducted in northern Europe and North America, with large parts of the world totally unrepresented. In the associations between the number of environmental risk studies for schizophrenia with potential predictors, we found that neither population nor wealth or research investment were strong predictors of research outputs in the field. Interestingly, the stronger correlations were found for number of researchers per population and for indicators of top-end scientific achievements, such as number of Nobel laureates per country.

Our results demonstrate a gap of knowledge due to the underrepresentation of studies on environmental risk of schizophrenia spectrum disorders in large parts of the world. This has implications not only in the generalisability of any findings from research conducted in the Northern hemisphere but also in our ability to progress in efforts to make causal inferences about biological pathways to schizophrenia. These findings reinforce the need to focus research on populations that are underrepresented in research and underserved in health care.

We evaluated performance-based differences in neuropsychological functioning in older adults (age 65+) across the dementia continuum (cognitively intact, mild cognitive impairment, and dementia) according to recent cannabis use (past six months).

A sample of 540 older adults from a well-characterized observational cohort was included for analysis. Participants completed a standardized questionnaire assessing cannabis use in the six months prior to the study visit and completed a comprehensive neuropsychological assessment. We used traditional cross-sectional analyses (multivariate, univariate) alongside causal inference techniques (propensity score matching [PSM]) to evaluate group differences according to recent cannabis use status. We also examined whether cannabis-related problem severity, a risk factor for cannabis use disorder (CUD), was associated with cognitive outcomes among those reporting recent cannabis use.

Approximately 11% of participants reported using cannabis in the prior six months, with the median user consuming cannabis two to four times per month. Participants with recent cannabis use performed similarly across all five domains of neuropsychological functioning compared to those with no cannabis use. Among older adults reporting recent cannabis use, those with elevated risk for CUD demonstrated lower memory performance.

These preliminary results are broadly consistent with other findings indicating that low-frequency cannabis use among older adults, including those along the dementia continuum, is generally well tolerated from a cognitive perspective. However, among older adults who used cannabis, elevated symptoms of CUD may negatively impact memory performance. Future research should explore how variations in cannabis use patterns, individual characteristics, and clinical phenotypes influence cognitive outcomes.

Cannabis use in young adulthood is common, yet few studies have explored how it predicts changes in psychopathology and functional well-being in community samples. We assessed these links using both self-reported frequency of cannabis use and hair THC concentrations.

Data came from a community sample of young adults (N = 863) who reported cannabis use (weekly-to-daily use: n = 150) and provided hair samples at age 20 (cannabis detected: n = 110). Liquid chromatography–tandem mass spectrometry quantified delta-9-tetrahydrocannabinol (THC) and cannabinol (CBN) concentrations in hair. At ages 20 and 24, participants reported psychopathology (psychotic-like experiences, problematic substance use, internalizing symptoms, and aggression) and functional wellbeing (general well-being, delinquency, and not being in employment, education, or training). Multiple linear and logit regression models tested associations between six different continuous and dichotomous operationalizations of self-reported and objective cannabis exposure at age 20 and psychological and functional well-being at age 24, adjusting for sex, sociodemographic characteristics, and the outcomes measured at age 20.

Both self-reported frequency of cannabis use and hair THC concentrations predicted increases in psychotic-like experiences and internalizing symptoms, increased aggression, decreased general well-being, higher odds of not being in employment, training, or education, and more problematic substance use from age 20 to 24, with small effect sizes. Composite exposure scores derived from self-reports and hair data were not more informative than either source alone.

Frequent cannabis use predicted adverse changes in psychopathological outcomes from ages 20 to 24, regardless of how it was assessed.

Cannabis use is elevated in youth with depression and attention-deficit/hyperactivity disorder (ADHD), but drivers of this increase remain underexplored. The self-medication hypothesis suggests cannabis is used by patients for mood regulation, a common difficulty in ADHD and depression. This study aimed to examine associations between mood instability and cannabis use in a large, representative clinical cohort of adolescents diagnosed with ADHD and/or depression.

Natural language processing (NLP) approaches were utilised to identify references to mood instability and cannabis use in the electronic health records of adolescents (aged 11–18 years) with primary diagnoses of ADHD (n = 7,985) or depression (n = 5,738). Logistic regression was used to examine mood instability as the main exposure for cannabis use in models stratified by ADHD and depression.

Mood instability was associated with a 25% higher probability of cannabis use in adolescents with ADHD compared to those with depression. Following adjustment for available sociodemographic and clinical covariates, mood instability was associated with increased cannabis use in both ADHD (aOR: 1.61 [95% CI: 1.41–1.84]) and depression (aOR: 1.38 [95% CI: 1.21–1.57]) groups.

This was the first study to explore the differential impact of mood instability on adolescent cannabis use across distinct diagnostic profiles. NLP analysis proved an efficient tool for examining large populations of adolescents accessing psychiatric services and provided preliminary evidence of a link between mood instability and cannabis use in ADHD and depression. Longitudinal studies using direct measures or tailored NLP techniques can further establish the directionality of these associations.

Cannabis use is linked to treatment non-adherence and relapses in psychotic disorders. Antipsychotic medication is effective for relapse prevention in primary psychoses, but its effectiveness after cannabis-induced psychosis (CIP) remains unclear.

To examine the effectiveness of antipsychotic medication for relapse prevention following the first clinically diagnosed CIP.

A cohort of 1772 patients (84.1% men) with incident CIP was identified from the Swedish National Patient and Micro Data for Analyses of Social Insurance registers. The primary outcome was hospitalisation due to any psychotic episode. Drug use data were collected from the Prescribed Drug Register and modelled into drug use periods using the PRE2DUP method. A within-individual Cox regression model was used to study the risk of outcomes during the use of different oral or long-acting injectable (LAI) antipsychotics compared with non-use.

The mean age at first diagnosis was 26.6 years (s.d. = 8.3). Of the cohort, 1343 (75.8%) used antipsychotics and 914 (51.3%) experienced psychosis hospitalisation during the follow-up. Any antipsychotic use was associated with a decreased risk of psychosis hospitalisation (adjusted hazard ratio (aHR) 0.75; 95% CI 0.67–0.84). Specific antipsychotics associated with decreased risk included aripiprazole LAI (aHR 0.27; 95% CI 0.14–0.51), olanzapine LAI (aHR 0.28; 95% CI 0.15–0.53), clozapine (aHR 0.55; 95% CI 0.34–0.90), oral aripiprazole (aHR 0.64; 95% CI 0.45–0.91), antipsychotic polytherapy (aHR 0.74; 95% CI 0.63–0.87) and oral olanzapine (aHR 0.81; 95% CI 0.69–0.94).

In particular, LAIs, clozapine and oral aripiprazole were associated with a decreased risk of psychosis relapse following CIP. Prescribers should consider using more LAIs for better treatment outcomes after CIP.

Since cannabis was legalized in Canada in 2018, its use among older adults has increased. Although cannabis may exacerbate cognitive impairment, there are few studies on its use among older adults being evaluated for cognitive disorders.

We analyzed data from 238 patients who attended a cognitive clinic between 2019 and 2023 and provided data on cannabis use. Health professionals collected information using a standardized case report form.

Cannabis use was reported by 23 out of 238 patients (9.7%): 12 took cannabis for recreation, 8 for medicinal purposes and 3 for both purposes. Compared to non-users, cannabis users were younger (mean ± SD 62.0 ± 7.5 vs 68.9 ± 9.5 years; p = 0.001), more likely to have a mood disorder (p < 0.05) and be current or former cigarette smokers (p < 0.05). There were no significant differences in sex, race or education. The proportion with dementia compared with pre-dementia cognitive states did not differ significantly in users compared with non-users. Cognitive test scores were similar in users compared with non-users (Montreal Cognitive Assessment: 20.4 ± 5.0 vs 20.7 ± 4.5, p = 0.81; Folstein Mini-Mental Status Exam: 24.5 ± 5.1 vs 26.0 ± 3.6, p = 0.25). The prevalence of insomnia, obstructive sleep apnea, anxiety disorders, alcohol use or psychotic disorders did not differ significantly.

The prevalence of cannabis use among patients with cognitive concerns in this study was similar to the general Canadian population aged 65 and older. Further research is necessary to investigate patients’ motivations for use and explore the relationship between cannabis use and mood disorders and cognitive decline.

Vaping is increasing in popularity. Vape products are offered in a wide variety and promise to reduce harms associated with cigarette smoking, among other claims. The motivations for vaping in patients with substance use disorder are largely unknown.

To describe perceptions and motivations regarding vaping among patients with opioid use disorder (OUD) who vape.

A convergent mixed-methods study design was used, and individual, semi-structured interviews were conducted with 41 individuals with OUD who were receiving medication for OUD and also vaped. An inductive data-driven approach was employed to characterise perspectives on vaping.

The mean ages at which participants had been introduced to vaping and initiated regular vaping were 33.95 years (s.d. 12.70) and 34.85 years (s.d. 12.38), respectively. Daily vaping (85%) of nicotine, flavoured nicotine or cannabis was common, with 27% reporting vaping both nicotine and cannabis. Qualitative analysis identified 14 themes describing motivations for vaping, including viewing vaping as a smoking cessation tool, convenience and popularity among youth.

Mixed-methods findings indicated that patients with OUD who vape perceived vaping to be healthier, cleaner and more convenient than cigarette and cannabis smoking, without appreciating the health risks. The perspectives reflected the importance of health education, guidelines and screening tools for vaping and could provide direction for healthcare providers and future vaping cessation programmes.

Cannabis is one of the most commonly used drugs globally, although its legal status varies across regions. Public support for its decriminalization has increased, but gaps in our understanding of the health consequences of cannabis use remain, particularly related to its impact on mental health. This article provides an updated systematic review and meta-analysis (previous being Lev-Ran et al., 2014) looking at the relationship between cannabis and depression.

Literature available before March 2023 was screened for longitudinal studies that included cannabis use and depression. Cross-sectional studies and those only looking at special populations were excluded. Studies must have also controlled for depression at baseline to allow for investigation of a temporal relationship. Extracted data included cannabis measures, depression outcomes, adjusted odds ratios, and study settings. Meta-analysis employed a random effects model with multilevel meta-regression for effect size moderators.

The search yielded 1,599 titles from various databases, resulting in 22 studies for meta-analysis, including 14 from Lev-Ran et al. Eleven studies were US-based, with participants mostly under 18. Meta-analysis showed a higher risk of depression among cannabis users (OR: 1.29, 95% CI: 1.13–1.46). Risk of bias assessment showed medium risk across studies with exposure measurement being a key bias area. The funnel plot and Egger’s Sandwich test did not suggest publication bias.

This study underscores the association between cannabis use and depression but also emphasizes the need for further research, especially in understanding usage patterns, heavy use definitions, and long-term effects on depression risk amidst changing cannabis trends.

Previous studies identified clusters of first-episode psychosis (FEP) patients based on cognition and premorbid adjustment. This study examined a range of socio-environmental risk factors associated with clusters of FEP, aiming a) to compare clusters of FEP and community controls using the Maudsley Environmental Risk Score for psychosis (ERS), a weighted sum of the following risks: paternal age, childhood adversities, cannabis use, and ethnic minority membership; b) to explore the putative differences in specific environmental risk factors in distinguishing within patient clusters and from controls.

A univariable general linear model (GLS) compared the ERS between 1,263 community controls and clusters derived from 802 FEP patients, namely, low (n = 223) and high-cognitive-functioning (n = 205), intermediate (n = 224) and deteriorating (n = 150), from the EU-GEI study. A multivariable GLS compared clusters and controls by different exposures included in the ERS.

The ERS was higher in all clusters compared to controls, mostly in the deteriorating (β=2.8, 95% CI 2.3 3.4, η2 = 0.049) and the low-cognitive-functioning cluster (β=2.4, 95% CI 1.9 2.8, η2 = 0.049) and distinguished them from the cluster with high-cognitive-functioning. The deteriorating cluster had higher cannabis exposure (meandifference = 0.48, 95% CI 0.49 0.91) than the intermediate having identical IQ, and more people from an ethnic minority (meandifference = 0.77, 95% CI 0.24 1.29) compared to the high-cognitive-functioning cluster.

High exposure to environmental risk factors might result in cognitive impairment and lower-than-expected functioning in individuals at the onset of psychosis. Some patients’ trajectories involved risk factors that could be modified by tailored interventions.

Despite one-third of patients with cancer using cannabis for symptom management, little is known about their access to and usage of cannabis. Community Engagement (CE) studios involving community experts with chronic health conditions were used to inform a qualitative study on access to and use of cannabis products among patients with cancer.

We conducted two 2-hour CE studios with residents from Western NY (WNY) (N = 18). Our sample primarily included White and Black residents (56% vs. 39%). After a researcher-led 10-minute presentation, a community facilitator led the discussion, which focused on questions about challenges to cannabis use, recommendations for providers when discussing cannabis with patients, and community factors influencing use.

Community experts reported that state legalization of cannabis made it easier to access cannabis, but the costs of cannabis and distance to dispensaries hindered their ability to obtain it. Discrimination was also a key barrier to medical cannabis receipt. There were differences in the perceived safety of where to obtain cannabis (dispensaries vs. friends). Community experts wanted providers to be more informed and less biased about recommending cannabis. Community experts recommended conducting focus groups for the subsequent study to ask questions about cannabis use.

The CE studios encouraged us to switch formats from qualitative interviews to focus groups and provided guidance on question topics for the subsequent study. Incorporating community expert’s feedback through CE studios is an effective strategy to design more impactful studies.