A systematic review of 29 studies examined whether the psychoactive effects of ketamine are linked to its therapeutic benefits for psychiatric disorders. About half of the studies (51.72%) found a positive relationship between ketamine-induced altered states of consciousness and clinical outcomes, while 44.83% found no link, and one study found a negative association. For mood disorders like major depressive disorder and bipolar disorder, 48% of studies showed a positive relationship and 48% showed none. All three studies on substance use disorder reported a positive correlation. The authors conclude the relationship remains uncertain due to high variability across studies.
A meta-analysis of eleven studies found no significant correlation between the psychoactive (psychomimetic) effects of ketamine and clinical outcomes in mental illness, including depression. The overall correlation was r = 0.06, and for depression specifically r = 0.03, both non-significant. Sub-analyses accounting for patient disorders, intravenous administration, assessment instruments, and timing also yielded no significant findings. High heterogeneity was present. The analysis suggests that altered states of consciousness during ketamine sessions are not directly linked to clinical outcomes, but the limited number of studies and heterogeneity make this conclusion preliminary.
Adults with major depressive disorder who report higher levels of dispositional mindfulness—the tendency to attend to present-moment experiences with openness and awareness—show fewer depressive and anxiety symptoms, better sleep quality, and higher self-esteem compared to those with lower trait mindfulness. In a cross-sectional study of 97 adults diagnosed with MDD, two clusters emerged: a High Trait group and a Low Trait group. The High Trait group had significantly lower depressive symptoms (d = 0.795) and anxiety symptoms (d = 0.739), and higher self-esteem (d = -0.586) and sleep quality (d = 0.460). These results suggest trait mindfulness may protect against poor mental health in depression.