Neurocognitive performance of repeated versus single intravenous subanesthetic ketamine in treatment resistant depression

•Baseline working memory is a predictor of antidepressant response to repeated ketamine.•Most neurocognitive performance at the end of treatment remain stable or improved to repeated or single ketamine.•Speed of processing, set shifting, and spatial working memory improved in the six ketamine group.•These cognitive improvements from baseline to the end of treatment was independent of changes in depression.