Intermediate: cognitive phenotypes in bipolar disorder.
BACKGROUND
Intermediate cognitive phenotypes (ICPs) are measurable and quantifiable states that may be objectively assessed in a standardized method, and can be integrated into association studies, including genetic, biochemical, clinical, and imaging based correlates. The present study used neuropsychological measures as ICPs, with factor scores in executive functioning, attention, memory, fine motor function, and emotion processing, similar to prior work in schizophrenia.


METHODS
Healthy control subjects (HC, n=34) and euthymic (E, n=66), depressed (D, n=43), or hypomanic/mixed (HM, n=13) patients with bipolar disorder (BD) were assessed with neuropsychological tests. These were from eight domains consistent with previous literature; auditory memory, visual memory, processing speed with interference resolution, verbal fluency and processing speed, conceptual reasoning and set-shifting, inhibitory control, emotion processing, and fine motor dexterity.


RESULTS
Of the eight factor scores, the HC group outperformed the E group in three (Processing Speed with Interference Resolution, Visual Memory, Fine Motor Dexterity), the D group in seven (all except Inhibitory Control), and the HM group in four (Inhibitory Control, Processing Speed with Interference Resolution, Fine Motor Dexterity, and Auditory Memory).


CONCLUSIONS
The HM group was relatively small, thus effects of this phase of illness may have been underestimated. Effects of medication could not be fully controlled without a randomized, double-blind, placebo-controlled study.


CONCLUSIONS
Use of the factor scores can assist in determining ICPs for BD and related disorders, and may provide more specific targets for development of new treatments. We highlight strong ICPs (Processing Speed with Interference Resolution, Visual Memory, Fine Motor Dexterity) for further study, consistent with the existing literature.
Department of Psychiatry, University of Michigan, Depression Center, Ann Arbor, MI, United States. slangen@umich.edu
Scott A
SA
Langenecker
Erika F H
EF
Saunders
Allison M
AM
Kade
Michael T
MT
Ransom
Melvin G
MG
McInnis
D000328:Adult; D001307:Auditory Perception; D001714:Bipolar Disorder / Q000523:psychology*; D003071:Cognition; D003210:Concept Formation; D003863:Depression / Q000523:psychology*; D005260:Female; D006801:Humans; D007266:Inhibition, Psychological; D007508:Irritable Mood; D008297:Male; D008568:Memory; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D011597:Psychomotor Performance; D011930:Reaction Time; D012720:Severity of Illness Index; D014705:Verbal Behavior; D014796:Visual Perception