Joshua D. Rosenblat, MD, MSc, of the University Health Network in Toronto, and co-authors reported in JAMA Psychiatry that four ketamine infusions significantly reduced depression severity in 63 outpatients with treatment-resistant bipolar I or II depression compared with midazolam, with a between-group difference of -7.3 points on the Montgomery-Åsberg Depression Rating Scale (95% CI -12.0 to -2.5, P=0.003). ^[1] The clinical trial published in JAMA Psychiatry found that ketamine infusions reduced depressive symptoms for more than 35% of participants compared to fewer than 12% in the control group. ^[2] The study authors reported that response rates, defined as a greater than 50% reduction on the Montgomery-Åsberg Depression Rating Scale, were higher in the ketamine group (35.3% vs 11.8%) and remission rates, defined as MADRS scores below 13, were also higher (17.6% vs 8.8%). ^[3] The study authors wrote that ketamine was not associated with treatment-emergent mania or psychosis, and no cases of mania, hypomania, psychosis, or suicide attempts were observed in either the ketamine or midazolam group. ^[4] Greg Rennie, a 61-year-old participant in a University Health Network clinical trial, reported his bipolar depression rating dropped from 8 out of 10 to 0 out of 10 after receiving ketamine infusions. ^[5] Ketamine treatment is not covered by most provincial health insurance in Canada, with private community clinics charging approximately $4,200 for a full cycle of six treatments. ^[6] The study found that patients' symptoms returned after they stopped the infusions, suggesting they would need maintenance sessions to keep up the antidepressant effects. ^[7]