Ketamine lowers depressive symptoms after surgery even when given only under general anesthesia

Ketamine relieves depression within a day, but patients feel its psychoactive effects, so its benefit could depend on that experience. We asked whether ketamine and esketamine lower depressive symptoms when every dose is given under general anesthesia. Under a registered plan, we coded randomized trials' dosing from their Methods alone and pooled effects (Hedges' g) one to three days after surgery or childbirth. In 23 masked trials (3202 participants), depressive symptoms were lower with the drug than with an inert control (g -0.61, confidence interval -0.81 to -0.4; Holm-adjusted p < 0.001), though trials varied widely. Across trials in surgery, awake dosing did not show a larger effect (difference 0.12, -0.24 to 0.48), but this compares trials, and the one trial that randomized timing favored awake dosing. Masked doses also lowered pain. Ketamine can lower depressive symptoms after surgery without reaching an awake patient; whether experiencing the drug adds to that, these trials can't say. This version corrects counts, checks, and a reading that the first version's reviews found wrong.