title: Khat use is associated with increased response conflict in humans.
abstract: OBJECTIVE
  Khat consumption has become a worldwide phenomenon broadening from Eastern Africa and the south west of the Arabian Peninsula to ethnic communities in the rest of the world. Only few studies have systematically looked into cognitive impairments in khat users. We studied whether khat use is associated with changes in the emergence and resolution of response conflict, a central cognitive control function.
  
  
  METHODS
  Khat users (n = 16) and khat-free controls (n = 16) were matched in terms of sex, ethnicity, socio-economical situation, age, alcohol and cannabis consumption, and IQ (Raven's Progressive Matrices). Groups were tested on response conflict, as measured by the Simon task.
  
  
  RESULTS
  Khat users performed significantly slower than controls and were more strongly affected by stimulus-induced response conflict.
  
  
  CONCLUSIONS
  Khat use is associated with specific impairments in behavioral control: general slowing and less efficient resolution of response conflicts, which is likely to impair decision making in everyday life.
authors.affiliation: Institute for Psychology, Leiden University, Wassenaarseweg 52, 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; D000704:Analysis of Variance; D016022:Case-Control Studies; D029754:Catha / Q000009:adverse effects*; D003220:Conflict, Psychological; D004192:Discrimination, Psychological / Q000187:drug effects; D005260:Female; D006801:Humans; D007361:Intelligence Tests; D016014:Linear Models; D008297:Male; D009426:Netherlands; D010936:Plant Extracts / Q000009:adverse effects*; D011597:Psychomotor Performance / Q000187:drug effects; D011930:Reaction Time / Q000187:drug effects; D013997:Time Factors; D055815:Young Adult
chemical_list: D010936:Plant Extracts