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Memory and verbal learning functions in twins with bipolar-I disorder, and the role of information-processing speed

Published online by Cambridge University Press:  21 January 2005

TUULA KIESEPPÄ
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
ANNAMARI TUULIO-HENRIKSSON
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
JARI HAUKKA
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
THEO VAN ERP
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
DAVID GLAHN
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
TYRONE D. CANNON
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
TIMO PARTONEN
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
JAAKKO KAPRIO
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA
JOUKO LÖNNQVIST
Affiliation:
Department of Mental Health and Alcohol Research, National Public Health Institute, Helsinki, Finland; Department of Public Health, University of Helsinki, Helsinki, Finland; Department of Psychology, UCLA, California, USA; Department of Psychiatry and Research Imaging Center, University of Texas, San Antonio, Texas, USA

Abstract

Background. Euthymic bipolar-I disorder (BP I) patients and their siblings have shown impairments in verbal learning and memory functions compared with controls, suggesting that these impairments may be genetic in origin. Reduced information-processing speed has been associated with impaired memory in the elderly, and recently in schizophrenia. The authors compared verbal learning and memory functioning in twins with BP I and co-twins to control twins, and examined whether the observed deficits are related to information-processing speed.

Method. Finnish Medical and Population Registers and Twin Cohorts were used to identify the BP I and control twins. Neuropsychological tests assessing verbal learning and memory, working memory, facial recognition, visual memory, and information-processing speed were administered to 26 BP I twins, 19 non-bipolar co-twins, and 114 controls. Group differences were analyzed by generalized estimation equation modeling.

Results. BP I patients, but not co-twins, showed impairments in all memory tests compared with controls. Female co-twins showed impairment in verbal learning and memory. Information-processing speed had a significant effect on encoding and learning efficiency.

Conclusions. This study showed for the first time that information-processing speed is related to memory functioning and verbal learning in BP I in a population-based, representative and euthymic sample. Furthermore, the data support the view that defects in verbal memory may be related to the genetic factors predisposing to BP I in females.

Type
Research Article
Copyright
© 2004 Cambridge University Press

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