Emotion regulation deficits specific to bipolar I disorder

By Lucy Piper, Senior medwireNews Reporter

Emotion regulation deficits associated with bipolar I disorder (BD-I) may not extend to bipolar II disorder (BD-II), say researchers.

Both groups showed increased emotional reactions during an attention control task in the presence of emotional distractors, but while in BD-I patients there was evidence of behavioural, functional connectivity and white matter microstructure deficits, this was not the case for BD-II patients.

The findings “emphasize deficient emotion regulation in the pathophysiology of the disorder, but suggest important differences between BD-I and BD-II in this process”, comments the team, led by Xavier Caseras (Cardiff University, UK).

The participants, comprising 16 euthymic patients with BD-I, 19 euthymic patients with BD-II and 20 mentally healthy controls, completed a 2-back working memory task, during which targets were sometimes flanked by two identical emotional facial expressions – neutral, fear or happy.

The presence of any of these emotional distractors significantly slowed the reaction times of patients with BD-I compared with healthy controls and BD-II patients, whereas there was no difference between healthy controls and BD-II patients. Most notably, the average reaction time of BD-I patients slowed significantly from approximately 680 msec when there were no distractors to 775 msec in the presence of fear distractors. For BD-II patients, there was no significant change in response time during any distractor.

Both groups of BD patients showed increased blood oxygenation level-dependent (BOLD) responses in the dorsolateral prefrontal cortex (DLPFC) and amygdala during the presence of fear distractors compared with healthy controls. But only BD-I patients showed increased inverse functional connectivity between the DLPFC and amygdala. In BD-II patients, the functional connectivity between these regions was, in fact, heightened in the presence of fear distractors.

In line with the behavioural and functional magnetic resonance imaging findings, BD-I patients showed reduced fractional anisotropy in the right uncinate fasciculus, compared with BD-II patients and healthy controls, who did not differ from each other.

“This finding further supports emotion regulation circuitry abnormalities being specific to BD-I and not generalized to BD-II”, say Caseras et al in Bipolar Disorders.

The findings indicated that “the less compromised the white matter in the uncinate fasciculus, as in subjects with BD-II relative to subjects with BD-I, the better the functional DLPFC–amygdala coupling during emotion regulation, resulting in better task performance”, they add.

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