People with alcohol use disorder experience changes in consciousness from 0.8 mg/kg intravenous ketamine administration. Ketamine's effects remain broadly consistent across three repeated infusions. Reductions in alcohol consumption linked to ketamine do not appear to be caused by the acute psychoactive effects of the drug.
Abruptly stopping heavy, daily cannabis use can trigger psychosis, both in people experiencing their first episode and in those with a pre-existing psychotic disorder. A systematic review of 21 studies identified 44 individuals whose psychosis began after cannabis withdrawal, and a health-record search found another 68 cases. Almost all were daily users who stopped abruptly. Those who resumed cannabis after the acute psychotic episode were far more likely to relapse than those who abstained (odds ratio 13.9). The findings indicate that acute psychotic symptoms can emerge after cannabis cessation, not only during its use.