Two intravenous infusions of ketamine (0.5 mg/kg) given 24 hours apart, added to usual treatment, led to full remission of suicidal ideas by day 3 in 63.0% of hospitalized patients with suicidal ideation, compared to 31.6% with placebo. The benefit was strongest in patients with bipolar disorder (odds ratio 14.1), not significant in those with depressive disorder (odds ratio 1.3), and intermediate for other disorders (odds ratio 3.7). At six weeks, remission remained high in the ketamine group (69.5% vs 56.3%) but was no longer statistically significant. Side effects were limited, with no manic or psychotic symptoms observed. An analgesic effect on mental pain may explain the anti-suicidal action.
Childhood adversity and cannabis use are both known risk factors for psychosis. This study examined whether cannabis use might explain the link between childhood adversity and psychotic disorders. Data from 881 first-episode psychosis patients and 1231 controls from the EU-GEI study showed that household discord was associated with psychosis partly through cannabis use. Lifetime cannabis use mediated 17% of the association, cannabis potency mediated 14%, and frequency of use mediated 29%. Similar results appeared for early exposure to household discord. The findings suggest that harmful cannabis use patterns partially explain how household discord leads to psychosis, and children exposed to challenging home environments could benefit from interventions to prevent cannabis misuse.