Cannabis and cognitive dysfunction: Parallels with endophenotypes of schizophrenia?

Cannabis and cognitive dysfunction: Parallels with endophenotypes of schizophrenia?

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J Psychiatry Neurosci 2007;32(1):30-52

Nadia Solowij, PhD; Patricia T. Michie, PhD

Neuroscience Institute for Schizophrenia and Allied Disorders Affiliated Scientists; Solowij — Illawarra Institute for MentalHealth and School of Psychology, University of Wollongong; Michie — Functional Neuroimaging Laboratory, School of Psychology, University of Newcastle, NSW, Australia

Abstract

Currently, there is a lot of interest in cannabis use as a risk factor for the development of schizophrenia. Cognitive dysfunction associated with long-term or heavy cannabis use is similar in many respects to the cognitive endophenotypes that have been proposed as vulnerability markers of schizophrenia. In this overview, we examine the similarities between these in the context of the neurobiology underlying cognitive dysfunction, particularly implicating the endogenous cannabinoid system, which plays a significant role in attention, learning and memory, and in general, inhibitory regulatory mechanisms in the brain. Closer examination of the cognitive deficits associated with specific parameters of cannabis use and interactions with neurodevelopmental stages and neural substrates will better inform our understanding of the nature of the association between cannabis use and psychosis. The theoretical and clinical significance of further research in this field is in enhancing our understanding of underlying pathophysiology and improving the provision of treatments for substance use and mental illness.

Résumé

La consommation de cannabis comme facteur de risque d’apparition de la schizophrénie suscite actuellement beaucoup d’intérêt. Le dysfonctionnement de la cognition associé à la consommation de longue durée ou importante de cannabis ressemble à de nombreux égards aux endophénotypes cognitifs que l’on a proposés comme marqueurs de la vulnérabilité à la schizophrénie. Dans cet aperçu, nous analysons les similitudes entre ces facteurs dans le contexte de la neurobiologie qui soustend le dysfonctionnement de la cognition, en mettant en cause particulièrement le système cannabinoïde endogène qui joue un rôle important dans l’attention, l’apprentissage et la mémoire et, en général, dans les mécanismes régulateurs de l’inhibition dans le cerveau. Une étude plus attentive des déficits de la cognition associés à des paramètres particuliers de la consommation de cannabis et aux interactions avec les stades neurodéveloppementaux et les substrats nerveux nous aidera à mieux comprendre la nature du lien entre la consommation de cannabis et la psychose. L’importance théorique et clinique de recherches plus poussées dans ce domaine vise à nous aider à mieux comprendre la pathophysiologie sous-jacente et à améliorer la prestation des traitements contre les toxicomanies et les maladies mentales.


Medical subject headings: cannabis; cognitive dysfunction; endophenotypes; schizophrenia; endocannabinoids.

Competing interests: None declared.

Acknowledgements: The authors are grateful to Sharon Monterrubio for assistance with manuscript preparation and to anonymous reviewers for their helpful suggestions.

Contributors: Dr. Solowij acquired the data and wrote the article. Both Drs. Solowij and Michie designed the review, analyzed the data, revised the article and gave final permission for it to be published.

Submitted June 2, 2006; Revised Aug. 16, 2006; Accepted Aug. 18, 2006

Correspondence to: Dr. Nadia Solowij, School of Psychology, University of Wollongong, Wollongong, NSW 2522 Australia; fax 61 2 4221 4163;nadia@uow.edu.au