title: Khat use is associated with impaired working memory and cognitive flexibility.
abstract: BACKGROUND
  Khat consumption has increased during the last decades in Eastern Africa and has become a global phenomenon spreading to ethnic communities in the rest of the world, such as The Netherlands, United Kingdom, Canada, and the United States. Very little is known, however, about the relation between khat use and cognitive control functions in khat users.
  
  
  OBJECTIVE
  We studied whether khat use is associated with changes in working memory (WM) and cognitive flexibility, two central cognitive control functions.
  
  
  METHODS
  Khat users and khat-free controls were matched in terms of sex, ethnicity, age, alcohol and cannabis consumption, and IQ (Raven's progressive matrices). Groups were tested on cognitive flexibility, as measured by a Global-Local task, and on WM using an N-back task.
  
  
  RESULTS
  Khat users performed significantly worse than controls on tasks tapping into cognitive flexibility as well as monitoring of information in WM.
  
  
  CONCLUSIONS
  The present findings suggest that khat use impairs both cognitive flexibility and the updating of information in WM. The inability to monitor information in WM and to adjust behavior rapidly and flexibly may have repercussions for daily life activities.
authors.affiliation: Institute for Psychological Research and Leiden Institute for Brain and Cognition, Leiden University, Leiden, The Netherlands. colzato@fsw.leidenuniv.nl
authors.forename: Lorenza S
authors.initials: LS
authors.lastname: Colzato
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Ruiz
authors.forename: Wery P M
authors.initials: WP
authors.lastname: van den Wildenberg
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hommel
mesh_terms: D000328:Adult; D000351:Africa, Eastern; D029754:Catha; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008569:Memory Disorders / Q000209:etiology*