Research Article

Khat use is associated with increased response conflict in humans

  1. Lorenza S. Colzato1,2,*,
  2. Manuel J. Ruiz1,2,
  3. Wery P. M. van den Wildenberg3 and
  4. Bernhard Hommel1,2

Article first published online: 15 MAY 2012

DOI: 10.1002/hup.2229

Issue

Human Psychopharmacology: Clinical and Experimental

Human Psychopharmacology: Clinical and Experimental

Volume 27, Issue 3, pages 315–321, May 2012


Additional Information

How to Cite

Colzato, L. S., Ruiz, M. J., van den Wildenberg, W. P. M. and Hommel, B. (2012), Khat use is associated with increased response conflict in humans. Hum. Psychopharmacol. Clin. Exp., 27: 315–321. doi: 10.1002/hup.2229

Author Information

  1. 1

    Institute for Psychology, Leiden University, Leiden, The Netherlands

  2. 2

    Leiden Institute for Brain and Cognition, Leiden, The Netherlands

  3. 3

    Amsterdam Center for the Study of Adaptive Control in Brain and Behaviour (Acacia), Psychology Department, University of Amsterdam, Amsterdam, The Netherlands

*L. S. Colzato, Leiden University, Institute for Psychology, Cognitive Psychology Unit, Wassenaarseweg 52, 2333 AK Leiden, The Netherlands. E-mail: colzato@fsw.leidenuniv.nl

Publication History

  1. Issue published online: 15 MAY 2012
  2. Article first published online: 15 MAY 2012
  3. Manuscript Accepted: 30 MAR 2012
  4. Manuscript Received: 20 OCT 2011

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Keywords:

  • khat;
  • response conflict;
  • Simon task;
  • dopamine

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.

Method

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. Copyright © 2012 John Wiley & Sons, Ltd.

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