Philadelphia, PA, October 11, 2012 - A paper by Shizhong Han and colleagues in the current issue of Biological Psychiatry implicates a new gene in the risk for cannabis dependence. This gene, NRG1, codes for the ErbB4 receptor, a protein implicated in synaptic development and function.

The researchers set out to investigate susceptibility genes for cannabis dependence, as research has already shown that it has a strong genetic component.

To do this, they employed a multi-stage design using genetic data from African American and European American families. In the first stage, a linkage analysis, the strongest signal was identified in African Americans on chromosome 8p21. Then using a genome-wide association study dataset, they identified one genetic variant at NRG1 that showed consistent evidence for association in both African Americans and European Americans. Finally, they replicated the association of that same variant in an independent sample of African-Americans.

All together, the findings suggest that NRG1 may be a susceptibility gene for cannabis dependence.

An interesting feature of this paper is that these findings may also suggest a link between the genetics of schizophrenia and the genetics of cannabis dependence. NRG1 emerged into public awareness after a series of genetic studies implicated it in the heritable risk for schizophrenia. Subsequent studies in post-mortem brain tissue also suggested that the regulation of NRG1 was altered in the brains of individuals diagnosed with schizophrenia.

Thus, the current findings may help to explain the already established link between cannabis use and the risk for developing schizophrenia. A number of epidemiologic studies have attributed the association of cannabis use and schizophrenia to the effects of cannabis on the brain rather than a common genetic link between these two conditions.

"The current data provide a potentially important insight into the heritable risk for schizophrenia and raise the possibility that there are some common genetic contributions to these two disorders," commented Dr. John Krystal, Editor of Biological Psychiatry.

However, further research will be necessary to further confirm the role that NRG1 plays in cannabis dependence and the potential link between cannabis use and psychosis.

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The article is "Linkage Analysis Followed by Association Show NRG1 Associated with Cannabis Dependence in African Americans" by Shizhong Han, Bao-Zhu Yang, Henry R. Kranzler, David Oslin, Raymond Anton, Lindsay A. Farrer, and Joel Gelernter (doi: 10.1016/j.biopsych.2012.02.038). The article appears in Biological Psychiatry, Volume 72, Issue 8 (October 15, 2012), published by Elsevier.

Notes for editors

Full text of the article is available to credentialed journalists upon request; contact Rhiannon Bugno at +1 214 648 0880 or Biol.Psych@utsouthwestern.edu. Journalists wishing to interview the authors may contact Joel Gelernter at +1 203 932 5711 Ext. 3590 or joel.gelernter@yale.edu.

The authors' affiliations, and disclosures of financial and conflicts of interests are available in the article.

John H. Krystal, M.D., is Chairman of the Department of Psychiatry at the Yale University School of Medicine and a research psychiatrist at the VA Connecticut Healthcare System. His disclosures of financial and conflicts of interests are available here.

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Biological Psychiatry is the official journal of the Society of Biological Psychiatry, whose purpose is to promote excellence in scientific research and education in fields that investigate the nature, causes, mechanisms and treatments of disorders of thought, emotion, or behavior. In accord with this mission, this peer-reviewed, rapid-publication, international journal publishes both basic and clinical contributions from all disciplines and research areas relevant to the pathophysiology and treatment of major psychiatric disorders.

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