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

Tuula Kieseppä, Annamari Tuulio-Henriksson, Jari Haukka, Theo Van Erp, David Glahn, Tyrone D. Cannon, Timo Partonen, Jaakko Kaprio, Jouko Lönnqvist

Research output: Contribution to journalArticlepeer-review

98 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)205-215
Number of pages11
JournalPsychological Medicine
Issue number2
StatePublished - Feb 2005
Externally publishedYes

ASJC Scopus subject areas

  • Applied Psychology
  • Psychiatry and Mental health


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