Fig. 2: Changes in depressive symptoms in non-improvers following six ketamine infusions.

Linear mixed models showed significant reductions in depressive symptoms from baseline to the end of treatment in patients with no improvement at 24 h post-infusion 4 (a), two consecutive non-improvements at 24 h post-infusion 3 (b), and three consecutive non-improvements at 24 h post-infusion 3 (c). Post hoc tests, after Sidak’s correction, revealed no significant changes from 24 h post-infusion 4 to the end in non-improvers at 24 h post-infusion 4 (a) and from 24 h post-infusion 3 to the end in those with three consecutive non-improvements at 24 h post-infusion 3 (c). However, depressive symptoms significantly decreased from 24 h post-infusion 3 to the end in patients with two consecutive non-improvements at 24 h post-infusion 3 (b; post-infusion 3 vs. 5: estimated marginal mean difference [EMMD], P = 0.033; post-infusion 3 vs. 6: EMMD = 5.480, P = 0.006). MADRS Montgomery–Åsberg Depression Rating Scale. *Significant difference at the given time point was found when compared to 24 h post-infusion 3 (paired t test, p < 0.05). **Significant difference at the given time point was found when compared to 24 h post-infusion 3 (paired t test, p < 0.01).