The authors of this paper do not have any commercial associations that might pose a conflict of interest in connection with this manuscript.
Differential working memory impairment in bipolar disorder and schizophrenia: effects of lifetime history of psychosis
Version of Record online: 15 MAR 2006
Volume 8, Issue 2, pages 117–123, April 2006
How to Cite
Glahn, D. C., Bearden, C. E., Cakir, S., Barrett, J. A., Najt, P., Serap Monkul, E., Maples, N., Velligan, D. I. and Soares, J. C. (2006), Differential working memory impairment in bipolar disorder and schizophrenia: effects of lifetime history of psychosis. Bipolar Disorders, 8: 117–123. doi: 10.1111/j.1399-5618.2006.00296.x
- Issue online: 15 MAR 2006
- Version of Record online: 15 MAR 2006
- Received 17 December 2004, revised and accepted for publication 15 September 2005
- bipolar disorder;
- delayed response task;
- digit span;
- psychotic features;
- schizoaffective disorder;
- working memory
Background: Although bipolar disorder and schizophrenia have long been viewed as distinct illnesses, there is growing evidence that these two complex diseases share some common genes, which may manifest as overlapping neuropsychological impairments. Although working memory dysfunction has been proposed to be central to the pathophysiology of schizophrenia, it has received less attention in studies of bipolar disorder.
Method: We applied measures of working memory to patients with schizophrenia (n = 15), patients with schizoaffective disorder (n = 15), patients with psychotic (n = 11) and non-psychotic (n = 15) bipolar disorder, and demographically matched healthy subjects (n = 32), in order to determine the extent to which these groups show common or unique impairments.
Results: While patients with bipolar disorder (with and without psychotic features) and those with schizophrenia/schizoaffective disorder were impaired on backward digit span, only patients with a lifetime history of psychotic features, regardless of diagnosis, were impaired on spatial delayed response task.
Conclusions: Backward digit span performance is comparable in bipolar disorder and schizophrenia, and may be an appropriate endophenotypic marker that cuts across diagnostic categories. In contrast, spatial working memory performance clearly distinguishes non-psychotic bipolar disorder patients from patients with functional psychosis.