title: Beyond the K-hole: a 3-year longitudinal investigation of the cognitive and subjective effects of ketamine in recreational users who have substantially reduced their use of the drug.
abstract: BACKGROUND
  Ketamine is a dissociative anaesthetic that is also a drug of abuse. Previous studies have demonstrated persisting episodic and semantic memory impairments in recreational ketamine users 3 days after taking ketamine. However, the degree to which these deficits might be reversible upon reduction or cessation of ketamine use was not known.
  
  
  OBJECTIVE
  To follow-up a population of ketamine users tested 3 years previously and examine whether impairments observed 3 days after drug use are enduring or reversible.
  
  
  METHODS
  Eighteen ketamine users and 10 polydrug controls from studies conducted between 3 and 4 years earlier were re-tested on the same battery of cognitive tasks and subjective measures. These tapped episodic, semantic and working memory and executive and attentional functioning. Subjective schizotypal, dissociative, mood and bodily symptoms were also examined and a drug use history recorded.
  
  
  RESULTS
  The ketamine users had reduced their frequency of use of ketamine by an average of 88.3%. Performance of ketamine users on tasks tapping semantic memory had improved and this improvement was correlated with their reduction in ketamine use. On tasks tapping episodic memory and attentional functioning, ketamine users still showed deficits compared to polydrug controls. Higher levels of schizotypal symptoms and perceptual distortions were exhibited by the ketamine group, although dissociative symptoms were similar to controls.
  
  
  CONCLUSIONS
  These findings indicate that semantic memory impairments associated with recreational ketamine are reversible upon marked reduction of use; however, impairments to episodic memory and possibly attentional functioning appear long-lasting. In addition, schizotypal symptoms and perceptual distortions may persist after cessation of ketamine use. Ketamine users, or potential users, should be aware of the enduring effects of this drug on aspects of memory and subjective experience.
authors.affiliation: Clinical Psychopharmacology Unit, University College London, London, UK. c.morgan@ucl.ac.uk
authors.forename: Celia J A
authors.initials: CJ
authors.lastname: Morgan
authors.forename: Lisa
authors.initials: L
authors.lastname: Monaghan
authors.forename: H Valerie
authors.initials: HV
authors.lastname: Curran
mesh_terms: D000328:Adult; D000700:Analgesics; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007649:Ketamine; D007806:Language Disorders / Q000139:chemically induced*; D008137:Longitudinal Studies; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors*; D019966:Substance-Related Disorders / Q000523:psychology*; D013997:Time Factors
chemical_list: D000700:Analgesics; D016194:Receptors, N-Methyl-D-Aspartate; D007649:Ketamine