To describe the demographic, clinical, and treatment characteristics of individuals admitted with hexahydrocannabinol (HHC)-associated psychosis and compare with cannabis-associated psychosis.

A retrospective chart review was undertaken of all admissions to the Adult Acute Mental Health Unit at University Hospital Galway, Ireland, between 1 May 2023 and 31 July 2025, with psychosis and documented HHC or cannabis use in the seven days preceding admission. Demographic, clinical, and treatment variables were compared across three groups: HHC-only, cannabis-only, and combined HHC + cannabis associated psychosis. Group differences were examined using ANOVA for continuous variables and Fisher’s exact tests for categorical variables, with repeated-measures ANOVA used to examine antipsychotic dosing. Analyses were exploratory in nature.

Thirty-three individuals (79% male) met inclusion criteria. All HHC-related cases occurred in a first episode of psychosis. Affective symptoms were more frequent in the HHC-only group (89%) than in the cannabis-only (54%) and combined HHC + cannabis groups (27%) (p = 0.024). Formal thought disorder appeared more common in HHC-exposed groups (80%) compared with cannabis-only presentations (38%), reaching statistical significance in an exploratory comparison between cannabis-only and combined HHC-exposed groups (p = 0.027). Urine toxicology screening for THC metabolites, length of stay and maximum antipsychotic dose were similar across groups.

In this cohort, HHC-associated psychosis was associated with higher rates of affective symptoms and formal thought disorder than cannabis-related presentations, despite otherwise similar clinical features. Findings are hypothesis-generating, given the exploratory analyses, small sample and uncorrected multiple testing. They suggest a potential role for novel cannabinoid screening to support earlier identification and management.

Post-traumatic stress disorder (PTSD) symptoms can fluctuate substantially over short periods, yet routine screening typically relies on infrequent self-report. Wearable sensors provide continuous behavioural and physiological signals that may help identify periods of elevated risk.

This study aimed to evaluate whether combining wearable sensor features with daily self-report data could identify short-term PTSD symptom increases among recently discharged veterans.

Seventy-four veterans wore commercial activity trackers and completed brief daily questionnaires over 87 days. For each participant, we defined an individual baseline by using the first 14 days of PTSD scores. Wearable variables were transformed into baseline-referenced deviation features to capture departures from personal norms. Missing data were addressed with multiple imputation by chained equations. Candidate predictors were prioritised with least absolute shrinkage and selection operator regression, and a set of machine-learning classifiers was evaluated. Primary performance was assessed by using the area under the precision–recall curve (PR AUC).

Across feature set sizes (k = 1–25), performance peaked at k = 17. At this iteration, LightGBM achieved the strongest discrimination (PR AUC 0.86 (s.d. 0.07); area under the receiver-operating characteristic curve 0.89 (s.d. 0.04)) with a precision of 0.67 (s.d. 0.08), recall of 0.64 (s.d. 0.08) and F1 of 0.65 (s.d. 0.07). Key predictors reflected a multimodal profile, combining self-reported affect and perceived stress with wearable indicators of sleep continuity, activity variability and autonomic regulation.

Baseline-referenced wearable features combined with daily self-report may help identify near-term PTSD symptom increases among recently discharged veterans with elevated PTSD symptoms and problematic cannabis use. Future work should validate performance in broader PTSD populations, including samples without problematic cannabis use.

Cannabis use is common in people with psychosis and is associated with poor outcomes.

To assess insight into cannabis use disorder, perceptions about how cannabis use influences mental health and the desire to change cannabis use among people with psychotic disorders.

Adults with a psychotic disorder and comorbid cannabis use disorder were asked about the impact of cannabis use on their illness and their desire to change cannabis use. Cannabis use disorder was determined using DSM-5 criteria. Participants completed the Substance Use Awareness and Insight Scale.

Sixty-two participants (mean age: 42 years; 95% male; 65% Black ethnicity; 85% severe DSM-5 cannabis use disorder) completed the study. The mean total Substance Use Awareness and Insight Scale score was 4.8 (s.d.: 2.1), with subdomain scores of 3.7 (s.d.: 2.8) for general illness awareness, 6.2 (s.d.: 2.8) for symptom attribution, 3.5 (s.d.: 2.9) for awareness of need for treatment and 5.6 (s.d.: 3.8) for awareness of negative consequences. Fifty-eight per cent said that cannabis use made their mental health ‘better’, whereas only 15% said it made it ‘worse’; 27% reported that cannabis made their psychotic symptoms ‘better’, and 21% said it made them ‘worse’. Nevertheless, more than half the sample (53%) said they wanted to reduce or stop using cannabis.

Many people with psychotic disorders have impaired insight into cannabis use disorder or believe that cannabis improves their mental health; these factors may contribute to persistent use in this population. Interventions that improve insight may help to address ambivalence and support those already wishing to reduce use.

The United Kingdom legalized medical cannabis in 2018, yet little is known about people using cannabis medically with and without a prescription. This study aimed to estimate: 1) the percentage of people reporting using cannabis medically with and without a prescription; 2) the sources; 3) products used; and 4) associations between frequent product use and medical cannabis status.

Data were from national repeat cross-sectional surveys conducted in 2023 and 2024. UK participants were aged 16–65 who used cannabis in the past 12 months (n = 4,414). Multivariable regression analyses estimated associations between outcomes and medical cannabis status.

Overall, 12.9% of respondents reported receiving a medical cannabis prescription, 35.9% reported medical use without a prescription, and 51.2% reported no medical use. Cannabis was sourced through diverse routes; only 10.9% of people with prescriptions obtained all their cannabis from a prescription. Respondents with a prescription had a higher probability of reporting frequent use of drops, capsules, vape oils, edibles, drinks, solid concentrates, hash/kief, and topicals (aRRs = range between 1.82 and 3.51)) and a higher probability of screening positive for high-risk use (aRR = 3.09; 2.51–3.79) than respondents who did not use medically.

People with medical cannabis prescriptions show a higher probability of frequent use of processed products and of meeting a threshold for high-risk use. Healthcare encounters during medical cannabis prescribing should discuss risks related to products, potency, and adverse effects such as cannabis use disorder.

Recently, there has been a significant rise in potency (% tetrahydrocannabinol (THC)) of cannabis products globally. As such, there is a need for a better understanding of the relationship between cannabis potency and mental health outcomes, especially in a developmentally vulnerable population such as adolescents and young adults.

The objective of this scoping review was to summarise existing literature investigating the potency of cannabis products as it relates to mental health outcomes in adolescents and young adults aged 14–25.

Systematic searches of MEDLINE, Embase, CINAHL and PsycINFO were conducted for relevant manuscripts up to October 2025. Following PRISMA-ScR guidelines, retrieved studies were then screened and data extracted by two independent reviewers.

Out of 11 225 studies identified by our searches, 71 were included in the review after screening. Compared with low-potency cannabis, our findings suggest that high-potency cannabis is more strongly associated with severe mental health issues, such as cannabis dependence, psychosis and cognitive deficits.

Overall, it was found that high-potency cannabis use (>15% THC) was associated with a great number and magnitude of adverse mental health outcomes. As such, the potency of cannabis products should be measured in future cannabis research that investigates short- and long-term outcomes. Additionally, the potency of cannabis products should be a consideration in any future cannabis regulatory policy discussions.

Substances, such as cannabis, alcohol, and nicotine, have each been associated with an increased risk of mental health concerns in adolescence. These substances are often taken concurrently and less is known about the effects of polysubstance use. We investigated the relationship between polysubstance use and psychopathology in adolescence including internalising, externalising behaviours, and psychotic experiences (PE). As a secondary analysis, we examined gender differences.

A sample of 4,404 15–16-year-old adolescents in 40 schools in Ireland was examined. Our exposure was single substance use (cannabis, alcohol, and nicotine) and polysubstance use within the past month. The outcome of interest was psychopathology, measured using the Strengths & Difficulties Questionnaire, and the Adolescent Psychotic Symptoms Scale. Associations were explored using mixed-effects logistic models.

Adjusted odds ratios were calculated to examine the associations between polysubstance use and each outcome, compared to substance-naive participants. A significant dose response relationship was observed, with increasing substance use associated with higher odds of general psychopathology (aOR range: 1.65–5.09), internalising behaviours (aOR range: 1.18–2.06), externalising behaviours (aOR range: 1.68–5.79), and PE (aOR range: 1.60–3.13). Females engaging in polysubstance use exhibited the poorest mental health outcomes.

This study highlights the strong associations between adolescent polysubstance use and emerging mental health problems. The findings reinforce the need for mental health services to take polysubstance use into consideration during intervention. Tailored public health messaging is required, acknowledging polysubstance use as a marker for poor mental health among adolescents and young adults.

In recent decades, the potency of cannabis resin increased globally, raising concerns, as higher potency has been associated with increased risk of psychiatric harms at the individual level. The aim here was to examine whether changes over time in the potency of seized cannabis resin samples were associated with psychiatric harms at the population level.

Data on ∆-9-tetrahydrocannabinol (THC) concentration in seized cannabis resin were obtained from forensic departments in Denmark (2000–2022), the country reporting the highest potency in Europe. Data on admissions to cannabis treatment, incidence of cannabis-induced psychosis, and dual diagnosis (schizophrenia and cannabis use disorder) were obtained from national registers. Time-dependent associations between potency and the outcomes were examined with mixed-effects linear regression models and associations across age and sex were explored. Candidate time lags were 0–10 years.

THC concentration increased almost fourfold: mean 8.3–31.2% from 2000 to 2022. In fully adjusted models, THC was positively associated with first-time cannabis treatment entry at lags of 0–6, strongest at year 0 (p < 0.0001); incidence of cannabis-induced psychosis at lags of 0–4, strongest at year 0 (p < 0.0001); and incidence of dual diagnosis at lags of 0–1, strongest at year 0 (p < 0.01). No positive associations were found in unadjusted models. Subgroup analyses indicated associations in older patients and women.

Potency of seized cannabis resin increased almost fourfold from 2000 to 2022. Changes in cannabis potency were positively associated with psychiatric harms at the population level across all outcomes.

Neurodevelopmental models regard impulsivity as a central risk factor for adolescent substance use. However, the practical utility of impulsivity in predicting substance use is complicated by variability among measures that encompass multiple methods and theoretical domains. Prior research has been constrained by cross-sectional designs, small sample sizes, and/or the use of a narrow subset of impulsivity measures.

Leveraging the ABCD dataset (n = 11,868), we identified and replicated correlations among impulsivity measures and assessed their prospective longitudinal and concurrent predictive utility regarding adolescent substance use outcomes before 15 years old. We then used simulation to inform how associations between impulsivity and substance use vary across sampling strategies (population vs. high-risk cohorts) and sample sizes.

Correlations between questionnaire and behavioral measures of impulsivity were small, and questionnaires significantly outperformed behavioral measures in predicting substance use initiation, largely due to the contribution of the CBCL externalizing scale. Predictions of substance use based on impulsivity were statistically detectable but small according to clinical standards (AUCs 0.6–0.76), exhibiting sensitivity to sample size and base rate of substance use, and thus, poor absolute predictive performance. Large samples (n > 1,000) were needed to achieve adequate power for impulsivity measures to predict substance use initiation.

These results support a significant but small contribution of impulsivity in predicting the onset of early adolescent substance use, indicating that these factors alone are insufficient for clinically deployable prediction. In community samples, large sample sizes are needed for reproducible impulsivity prediction of adolescent substance use.

Decades of research have identified a strong association between heavy cannabis use and schizophrenia (SCZ), with evidence of correlated genetic factors. However, many studies on the genetic relationship between cannabis use and psychosis have lacked data on both phenotypes within the same individuals, creating challenges due to unmeasured confounding. We aimed to address this by using multimodal data from the All of Us Research Program, which contains genetic data as well as information on SCZ diagnosis and cannabis use.

We tested the association between cannabis use disorder (CUD) and SCZ polygenic scores (PGSs) with SCZ and heavy cannabis use. We tested models where both CUD and SCZ PGSs were included as joint predictors of heavy cannabis use and SCZ case status. We defined three sets of cases based on comorbidities: relaxed (assessing for only the primary condition), strict (excluding comorbidity), and dual-comorbidity.

CUD and SCZ polygenic liability were independently associated with heavy cannabis use; the SCZ PGS effect was very modest. In contrast, both SCZ and CUD PGSs were independently associated with SCZ, with independent significant effects of CUD PGS. Polygenic liability to CUD was associated with SCZ in individuals without a documented history of cannabis use, suggesting widespread pleiotropy.

These findings underscore the need for comprehensive models that integrate genetic risk factors for heavy cannabis use to advance our understanding of SCZ etiology.