Ketamine-induced altered states of consciousness: a systematic review of implications for therapeutic outcomes in psychiatric practices.

Abstract

This systematic review aims to elucidate the nexus between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders. We searched three databases and used citation tracking to include 29 studies. Predominantly, mood disorders, including bipolar disorder (BD) and major depressive disorder (MDD) (MDD + BD: + n = 25 studies), a large part of them involve treatment-resistant patients (n = 14 studies), substance use disorder (SUD, n = 3 studies), and social anxiety disorder (SAD, n = 1 study). From all included studies (n = 29), 15 (51.72%) of them identified a positive relation between ketamine-induced altered states of consciousness and clinical outcomes, while 13 studies (44.83%) showed no linkage between them, and one study (3.45%) delineated a negative association. Focusing solely on intravenous (IV) ketamine infusions (n = 25), 14 studies (56%) reported a positive modulation of ketamine's psychoactive effects and therapeutic benefits, whereas 10 studies (40%) confirmed no relationship, and one study (4%) showed a negative association. The single study (33.34%) involving subcutaneous ketamine and all three studies (66.6%) intranasal administration did not demonstrate a significant interaction between ketamine's psychoactive effects and therapeutic response. All three SUD studies reported a positive correlation between ketamine's psychoactive effects and therapeutic response. In contrast, the single SAD study did not find a relationship between these parameters. For studies involving mood disorders (n = 25), 12 studies (48%) reported a positive relationship between psychoactive effects and therapeutic response. Others 12 studies (48%) identified a null relationship, and one study (4%) found a significant negative association. Although we have found a larger association than previous studies between ketamine's psychoactive properties and its efficacy in treating a broad spectrum of psychiatric disorders, its topic remains indeterminate, mainly due to the high heterogeneity.

In the evidence

This study is part of the evidence base for a synthesis in the library. Here is how each one recorded it.

• State of the evidence: Esketamine for anxiety ↕Mixed

  About half of the reviewed studies linked ketamine's psychoactive effects to better therapeutic outcomes while 13 of 29 found no linkage, and the single social anxiety disorder study found no relationship; the overall relationship remains indeterminate.

  Synthesized October 23, 2026

Comparable studies

Other systematic reviews and meta-analyses on esketamine for anxiety, most cited first.