Emotional bias in unaffected siblings of patients with bipolar I disorder.

Background: Bipolar disorder (BPD) research has identified a number of neurocognitive deficits as potential vulnerability markers; however, very few studies have focused on patterns of performance on affective processing tasks (e.g. affective Go/No-Go tasks) which may be more closely tied to the pathophysiology of the illness. We previously reported that stable BPD patients demonstrate a response bias toward negative affective stimuli as compared with healthy controls and schizophrenia patients. The goal of the current study was to expand upon these prior findings to investigate these patterns in the unaffected siblings of BPD patients.

Methods: An affective Go/No-Go test was used to evaluate inhibitory response to negatively-valenced, positively-valenced, and neutral stimuli in 20 unaffected siblings of bipolar I patients versus 20 healthy controls. Accuracy (d') and response bias (beta) served as dependent variables in a series of repeated measures ANCOVAs.

Results: We found a non-significant main effect for group when comparing accuracy performance (d') on the affective Go/No-Go of unaffected siblings versus healthy controls. However, very similar to the pattern that we previously reported in stable BPD patients, unaffected siblings showed a response bias (beta) toward negatively-valenced stimuli versus healthy controls [F=3.81; p=0.03].

Limitations: Small sample size.

Conclusions: The current results extend our recent work which suggested that stable bipolar patients attend more readily to negative target stimuli than do schizophrenic or healthy subjects. These data, indicating that unaffected siblings also demonstrate an affective processing bias, implicate this task as a potential endophenotype in BPD.