A meta-analysis of ten studies (three cohort, seven case-control) with 7,390 participants aged 12–65 found a log-linear dose-response association between cannabis use frequency and psychosis risk. The risk of psychosis significantly increased with weekly or more frequent use: weekly use showed a relative risk of 1.35 (95% CI 1.19–1.52) and daily use a relative risk of 1.76 (95% CI 1.47–2.12). Less frequent use (yearly or monthly) was not associated with a significant increase in risk. The authors conclude that frequent cannabis users are at increased risk of psychosis and recommend public health messages convey these risk thresholds.
A course of six sub-anesthetic ketamine infusions over four weeks helped patients with treatment-resistant depression discontinue long-term benzodiazepine or z-drug use. Of 22 patients, 91% (20/22) successfully stopped all such medications by the end of the infusions, confirmed by urine tests. Fewer than 25% experienced significant worsening of anxiety, depression, sleep problems, or suicidality during withdrawal. Over a mean follow-up of one year, 64% (14/22) remained abstinent. These preliminary results suggest ketamine infusions may facilitate benzodiazepine deprescription even in patients with active depression and significant comorbidity.
A new treatment combining ketamine infusions with acceptance and commitment therapy (ACT) may be feasible for people who have both alcohol use disorder and treatment-resistant depression. In an open-label trial at a Montreal hospital, 30 participants will receive six ketamine infusions plus eight weekly therapy sessions, either in person or online. The study primarily tests whether the combined approach is practical and acceptable by measuring completion rates, safety, and data quality. Exploratory measures will track changes in depressive symptoms, alcohol use, and quality of life. Some participants will also be interviewed about their experiences.
Cannabis use is increasingly normalized, and psychosis is a major adverse health outcome. This review identifies risk factors for cannabis-related psychosis: genetic predisposition, mental health and substance use histories, early age of first use, high frequency of use, high THC potency, mode of use, and co-use of other substances. The protective effects of CBD are uncertain. Continuous cannabis use may worsen psychosis treatment and medication effects. Combinations of risk factors further amplify the odds of adverse psychosis outcomes. Reducing these risk factors, short of abstinence, may decrease the risk of psychosis and protect cannabis users' health.