Background: Due to its rapid antidepressant effect, ketamine has recently been clinically translated for people with treatment-resistant depression. However, its cognitive profile remains unclear, particularly with repeated and higher doses. In the present study, we report the cognitive results from a recent large multicentre randomised controlled trial, the Ketamine for Adult Depression Study (KADS)., Methods: In this randomised, double-blind, active-controlled, parallel group, multicentre phase 3 trial study we investigated potential cognitive changes following repeated treatment of subcutaneous racemic ketamine compared to an active comparator, midazolam, over 4 weeks, which involved two cohorts; Cohort 1 involved a fixed dose treatment protocol (0.5 mg/kg ketamine), Cohort 2 involved a dose escalation protocol (0.5-0.9 mg/kg) based on mood outcomes. Participants with treatment-resistant Major Depressive Disorder (MDD) were recruited from 7 mood disorder centres and were randomly assigned to receive ketamine (Cohort 1 n = 33; Cohort 2 n = 53) or midazolam (Cohort 1 n = 35; Cohort 2 n = 53) in a 1:1 ratio. Cognitive measurements were assessed at baseline and at the end of randomised treatment., Results: Results showed that in Cohort 1, there were no differences between ketamine and midazolam in cognitive outcomes. For Cohort 2, there was similarly no difference between conditions for cognitive outcomes., Limitations: The study included two Cohorts with different dosing regimes., Conclusions: The findings support the cognitive safety of repeated fixed and escalating doses at least in the short-term in people with treatment resistant MDD., Competing Interests: Declaration of competing interest Dr. Loo is supported by a NHMRC Investigator Grant (1195651), is on the Clinical Advisory Board for Douglas Pharmaceuticals, and has received fees for the following: Janssen Cilag advisory board, Medical Director of Neurostimulation and Interventional Psychiatry at Ramsay Health Care, book royalties from Springer, speaker fees from the Australian Private Hospitals Association, Wesley Hospital ECT course, Royal Australian and New Zealand College of Psychiatrists Congress, Spanish Psychiatric Hospitalisation Units Conference, Japanese Society of Psychiatry and Neurology conference. In the last 36 months, Dr. Glozier has received speaker's bureau honoraria from Servier Laboratories, Janssen and Lundbeck, and served on Advisory Boards for Servier Laboratories, Esia, Seqirus and Lundbeck. Dr. Baune has received grants and served as consultant, advisor or CME speaker for the following entities: AstraZeneca, Bristol-Myers Squibb, Janssen, Lundbeck, Otsuka, Servier, the National Health and Medical Research Council, the Fay Fuller Foundation, the James and Diana Ramsay Foundation. He is supported by research grants from European Union, DFG (Germany) and NHMRC (Australia). Within the last 36 months, Dr. Glue has attended a Janssen New Zealand advisory board, and is named on a patent for a controlled release ketamine tablet developed by Douglas Pharmaceuticals. In the last 36 months, Dr. Martin has received research consulting fees from Douglas Pharmaceuticals for a clinical trial involving ketamine. Dr. Berk is supported by a NHMRC Senior Principal Research Fellowship [1156072]. In the last 3 years he received grant/research support from National Health and Medical Research Council, Wellcome Trust, Medical Research Future Fund, Victorian Medical Research Acceleration Fund, Centre for Research Excellence CRE, Victorian Government Department of Jobs, Precincts and Regions and Victorian COVID-19 Research Fund. He received honoraria/royalties from Springer, Oxford University Press, Cambridge University Press, Allen and Unwin, EPA Warsaw, Lundbeck, Controversias Barcelona, Servier, Medisquire, HealthEd, ANZJP, European Psychiatric Association, Janssen, Medplan, Milken Institute, RANZCP, Abbott India, ASCP, Headspace, Allori for Eisai, Otsuka, Global Congress of Biological Psychiatry India, St Bio Pharma and Sandoz. Dr. Carter has received educational and travel support from Servier, Astra Zeneca, Otsuka Australia, Merck Sharp & Dohme, and Janssen-Cilag in the past five years. He also served on an advisory board for the AFFINITY trial. Dr. Hackett was supported by an NHMRC fellowship from 2018 to 2021 (APP1141328) and was a named investigator on the NHMRC grant for this study (APP1105089). Dr. Hood has received speaker and consultancy fees from Janssen & Servier, served on advisory boards for Janssen and Lundbeck, and is a board member of UWA Young Lives Matter Foundation, International Master in Affective Neuroscience, and Journal of Psychopharmacology. Dr. Somogyi is a director of the Australian Medicines Handbook Pty Ltd. (unpaid) and has received funding support by the Australian and New Zealand College of Anaesthetists to investigate ketamine for chronic postsurgical pain. The following authors report no financial relationships with commercial interests: Ania Harvey, Dr. Natalie Mills, Dr. Shanthi Sarma, Mr. Dusan Hadzi-Pavlovic, Ms. Vanessa Dong, and Dr. Anthony Rodgers., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)