Intermediate cognitive phenotypes identified for bipolar disorder patients
MedWire News: Factor scores for cognitive performance allow the identification of intermediate cognitive phenotypes (ICPs) in bipolar disorder patients that may provide specific targets for the development of novel treatments, argue US scientists.
As many, but not all, patients with major depressive disorder, bipolar disorder, anxiety disorders, and schizophrenia have cognitive dysfunction, such dysfunction can be considered to be one of several possible intermediate phenotypes, which are likely to be underpinned by one or more genetic variants.
Noting that ICPs have been only rarely studied in bipolar disorder, Scott Langenecker and colleagues from the University of Michigan in Ann Arbor studied 34 healthy controls, 66 euthymic bipolar disorder patients, 43 depressed bipolar disorder patients, and 13 hypomanic/mixed bipolar disorder patients.
The participants were administered a neuropsychological battery covering the eight domains of 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.
MANOVA analysis revealed that there was a significant group effect in the eight factor scores, such that controls outperformed euthymic patients on processing speed with interference resolution, visual memory, and fine motor dexterity.
In addition, controls outperformed depressed patients on all factors aside from inhibitory control, and outperformed hypomanic/mixed patients on inhibitory control, processing speed with interference resolution, fine motor dexterity, and auditory memory.
Focusing on euthymic patients, the team found that the number of psychiatric hospitalizations correlated with four of eight factor scores, while the number of years of illness was linked to five factor scores.
Both of these clinical variables were also significantly correlated with the sum of all eight factor scores. Antipsychotic medication was the only drug class associated with factor scores.
The researchers conclude in the Journal of Affective Disorders: “We and others argue that there may be common ICPs for bipolar disorder and related disorders that can be pursued in future studies of phenotypes with subsequent integration of genetic data.
“As a result there could be an expectation of earlier identification and preventative or ameliorative treatment, or development of specific targets for novel treatments.”
MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009
By Liam Davenport