Neurocognitive performance as an endophenotype for bipolar disorder.

Area of Science:

• Psychiatry
• Neuroscience
• Genetics

Background:

• Bipolar disorder (BD) presents significant challenges in identifying underlying genetic liabilities due to its complexity and heterogeneity.
• Endophenotypes, or measurable manifestations of genetic risk, are a promising strategy to uncover these hidden liabilities.
• Neurocognitive performance is frequently proposed as a key endophenotype for BD.

Purpose of the Study:

• To identify and evaluate candidate endophenotypes for bipolar disorder.
• To assess the validity of neurocognitive domains as endophenotypes for BD based on established criteria.
• To determine the specificity of potential endophenotypes across related psychiatric conditions.

Main Methods:

• Systematic review of published literature on endophenotypes in BD.
• Extensive review of studies on cognitive deficits in BD from 2000 onwards.
• Application of established criteria for validating endophenotypes.

Main Results:

• Executive functioning and verbal memory were identified as the most promising candidate endophenotypes for BD.
• These domains, however, lack specificity, as similar deficits are observed in schizophrenia and severe/psychotic major depression.
• Significant between-study heterogeneity was noted, indicating a need for further investigation.

Conclusions:

• Executive functioning and verbal memory represent potential endophenotypes for bipolar disorder, but require further validation.
• The lack of specificity necessitates caution in their application for identifying genetic liability.
• Future research should explore quantitative traits over diagnostic categories for more robust endophenotype studies in BD.