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In and out of the K‐hole: a comparison of the acute and residual effects of ketamine in frequent and infrequent ketamine users

Helen Valerie Curran, Lisa Monaghan

Addiction May 1, 2001 DOI: 10.1046/j.1360-0443.2001.96574910.x (opens in new tab)

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Study at a glance

AI-extracted from the abstract
Characteristics Observational cohort Peer reviewed
Sample size 37
Population Frequent and infrequent ketamine users
Duration 3 days
Measures cognitive tasks tapping memory and attentional function, subjective scales (schizotypal symptomatology, dissociation, mood)
Topics Esketamine Ketamine
Key findings Frequent ketamine users showed significant impairments on episodic and semantic memory tasks three days after use, compared with infrequent users, with no persisting dissociative or schizotypal symptoms. The authors conclude that frequent use produces long-lasting memory deficits.

Abstract

Aims. Ketamine, a non‐competitive NMDA receptor antagonist, produces acute impairments of working, episodic and semantic memory along with psychotogenic and dissociative effects when a single dose is given to healthy volunteers. In recreational users, Curran & Morgan (2000) showed that ketamine produced the same acute effects but that 3 days after ingestion, ketamine users showed persisting memory impairment and elevated psychotogenic symptoms compared with controls. To explore whether such persisting effects reflect chronic effects of ketamine use, the present study compared frequent with infrequent users of ketamine on the night of drug use and again 3 days later. Design and participants. Eighteen frequent and 19 infrequent ketamine users were assessed on each test day on a range of cognitive tasks tapping memory and attentional function and on subjective scales (schizotypal symptomatology, dissociation, mood). Findings. Groups were broadly matched for polydrug use apart from ketamine which frequent users took significantly more often and in larger quantities than infrequent users. Acute effects on day 0 replicated previous findings. On day 3 frequent users showed significant impairments on tasks tapping episodic and semantic memory but there was no evidence of persisting dissociative or schizotypal symptoms. Conclusion. These findings indicate that frequent use of ketamine produces long‐lasting impairments in episodic memory and aspects of retrieval from semantic memory. Such effects accord with animal evidence of the effects of NMDA receptor blockade on memory. Those using, or contemplating using ketamine should be informed of these persisting, detrimental effects of the drug upon human memory.

Comparable studies

Other observational and cohort studies on ketamine, most cited first.

Study Year Design Participants
Taming the Ketamine Tiger Volunteers from a prison population 2010 Observational study n = 20
Increased spontaneous MEG signal diversity for psychoactive doses of ketamine, LSD and psilocybin Humans 2017 Observational study
Disruption of Frontal–Parietal Communication by Ketamine, Propofol, and Sevoflurane Surgical patients undergoing induction of anesthesia with intravenous ketamine 2013 Observational cohort n = 30
Do the dissociative side effects of ketamine mediate its antidepressant effects? Treatment-resistant inpatients with major depressive disorder or bipolar disorder 2014 Observational cohort n = 108
Concomitant BDNF and sleep slow wave changes indicate ketamine-induced plasticity in major depressive disorder Patients with treatment-resistant major depressive disorder 2012 Observational cohort n = 30

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Esketamine Ketamine