Long-Term Stability of Cognitive Impairment in Bipolar Disorder: A 2-Year Follow-Up Study of Lithium-Treated Euthymic Bipolar Patients
J Clin Psychiatry 2008;69(5):712-719
© Copyright 2014 Physicians Postgraduate Press, Inc.
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Objective: To determine the course of cognitive impairment of
bipolar disorder with a 2-year longitudinal study and to investigate whether
the neuropsychological profile is related to clinical and psychosocial
variables in a sample of lithium-treated euthymic bipolar outpatients.
Method: Thirty-three bipolar disorder patients (all of whom
were diagnosed according to DSM-IV-TR criteria and were treated during 2003 at
the Lithium Clinic Program at Santa Maria Hospital, Lleida, Spain) and 33
healthy, matched controls were cognitively assessed twice over a 2-year
follow-up period. All patients were receiving the same mood-stabilizer
pharmacotherapy (lithium) at the first evaluation, and they were euthymic
(Hamilton Rating Scale for Depression score lower than 8 and Young Mania Rating
Scale score lower than 6) for at least 3 months before both evaluations.
Cognitive assessment was performed by means of a neuropsychological test
battery tapping into the main cognitive domains (executive function, attention,
processing speed, verbal memory, and visual memory).
Results: Repeated-measures multivariate analysis of covariance
showed that there were main effects of group in the executive domain (p < .04)
and in processing speed (p < .04). Multiple linear regression analysis showed
that none of the variables predicted psychosocial functioning (as measured with
the Global Assessment of Functioning scale) (R2 = 0.12, F = 2.08, p
= .1). Multilevel logistic regression analysis showed that processing speed
appeared to be significant as an indicator of low work activity (Exp[B] = 1.25,
95% CI = 1.005 to 1.547, p = .04).
Conclusions: Executive function and processing speed are the
cognitive domains affected in euthymic bipolar outpatients, and such deficits
are maintained over time. Our results show that executive dysfunction is the
main long-term neuropsychological deficit of bipolar disorder. Slower
processing seems to be related to worse work adaptation.