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Review ARTICLE

This article is part of a Research Topic

Cannabis use and cognition in schizophrenia

Else-Marie Løberg^1,2* and Kenneth Hugdahl^1,2

Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway

Division of Psychiatry, Haukeland University Hospital, Bergen, Norway

People with schizophrenia frequently report cannabis use, and cannabis may be a risk factor for schizophrenia, mediated through effects on brain function and biochemistry. Thus, it is conceivable that cannabis may also influence cognitive functioning in this patient group. We report data from our own laboratory on the use of cannabis by schizophrenia patients, and review the existing literature on the effects of cannabis on cognition in schizophrenia and related psychosis. Of the 23 studies that were found, 14 reported that the cannabis users had better cognitive performance than the schizophrenia non-users. Eight studies reported no or minimal differences in cognitive performance in the two groups, but only one study reported better cognitive performance in the schizophrenia non-user group. Our own results confirm the overall impression from the literature review of better cognitive performance in the cannabis user group. These paradoxical findings may have several explanations, which are discussed. We suggest that cannabis causes a transient cognitive breakdown enabling the development of psychosis, imitating the typical cognitive vulnerability seen in schizophrenia. This is further supported by an earlier age of onset and fewer neurological soft signs in the cannabis-related schizophrenia group, suggesting an alternative pathway to psychosis.

Keywords:

schizophrenia, psychosis, cannabis, neurocognition, substance abuse, neuropsychological functioning, illegal drugs

Citation:

Løberg EM and Hugdahl K (2009). Cannabis use and cognition in schizophrenia. Front. Hum. Neurosci. 3:53. doi: 10.3389/neuro.09.053.2009

Received:

01 June 2009;

Paper pending published:

22 August 2009;

Accepted:

04 November 2009;

Published online:

24 November 2009.

Edited by:

Vince D. Calhoun, University of New Mexico, USA

Reviewed by:

Francesca Filbey, The Mind Research Network, USA
Vince D. Calhoun, University of New Mexico, USA

© 2009 Løberg and Hugdahl. This is an open-access article subject to an exclusive license agreement between the authors and the frontiers research foundation, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are credited.

*Correspondence:

Else-Marie Løberg, Division of Psychiatry, Helse-Bergen HF, Haukeland University Hospital, Forskningsenheten, Bergen Mental Health Research Center, 5045 Bergen, Norway. e-mail: else.marie.loeberg@psych.uib.no