In our Forum discussion "journal club" series, the editors of Schizophrenia Bulletin provide access to the full text of a recent article. A short introduction by a journal editor gets us started, and then it's up to our readers to share their ideas and insights, questions, and reactions to the selected paper. So read on".
Simonsen C, Sundet K, Vaskinn A, Birkenaes AB, Engh JA, Færden A, Jónsdóttir H, Ringen PA, Opjordsmoen S, Melle I, Friis S, Andreassen OA. Neurocognitive Dysfunction in Bipolar and Schizophrenia Spectrum Disorders Depends on History of Psychosis Rather Than Diagnostic Group. Schizophr Bull . 2009 May 14. Abstract
Background Text By Gunvant Thaker, Professor and Chief, Schizophrenia Related Disorders Program, Maryland Psychiatric Research Center and Deputy Editor, Schizophrenia Bulletin
Historically, there has been an interest in understanding the commonality and differences between the clinical manifestations of schizophrenia and bipolar disorder. With the field focusing on the next iteration of the Diagnostic and Statistical Manual of Mental Disorders, DSM-V, this interest has intensified. Recent genetic findings that implicate sharing of several vulnerability chromosomal loci and genes by the two disorders add further fuel (Berrettini, 2003; Craddock et al., 2006). If some of the etiological factors are shared between the disorders, one of the important questions is to what extent the phenotypic expressions overlap, and where the two disorders diverge.
In this context, the recent paper by Simonsen and colleagues provides interesting data on neurocognitive dysfunction in the two disorders. In a sample of over 500 subjects, Simonsen and colleagues administered a comprehensive cognitive battery. They found that bipolar patients with a history of psychosis showed similar cognitive dysfunction as observed in schizophrenia and schizoaffective disorder, while bipolar patients without a history of psychosis showed poor performance only in processing speed. Impairments in several of the cognitive functions assessed in the study are also observed in non-ill, first-degree relatives of schizophrenia probands and are moderately heritable. This raises an interesting question: does the shared cognitive dysfunction among schizophrenia and bipolar disorder patients mark the shared genetic effects that are associated with vulnerability to psychosis?
References: Simonsen C, Sundet K, Vaskinn A, Birkenaes AB, Engh JA, F"rden A, J"nsd"ttir H, Ringen PA, Opjordsmoen S, Melle I, Friis S, Andreassen OA. Neurocognitive Dysfunction in Bipolar and Schizophrenia Spectrum Disorders Depends on History of Psychosis Rather Than Diagnostic Group. Schizophr Bull . 2009 May 14. Abstract
Berrettini W. Evidence for shared susceptibility in bipolar disorder and schizophrenia. Am J Med Genet C Semin Med Genet . 2003 Nov 15 ; 123C(1):59-64. Abstract
Craddock N, O'Donovan MC, Owen MJ. Genes for schizophrenia and bipolar disorder? Implications for psychiatric nosology. Schizophr Bull . 2006 Jan 1 ; 32(1):9-16. Abstract