No differences in visual theory of mind abilities between euthymic bipolar patients and healthy controls

Research on theory of mind (ToM) abilities in patients with bipolar disorder has yielded conflicting results. Meta-analyses point to a stable moderate impairment in remitted patients, but factors such as subsyndromal symptoms, illness severity, and deficits in basic neurocognitive functions might act as confounders. Also, differences in deficits depending on task area (cognitive or affective) or task modality (visual or verbal) have been observed. This study aimed to test the hypothesis that euthymic bipolar patients would perform more poorly than healthy subjects on visual cognitive and visual affective ToM tasks. Furthermore, we aimed to explore the relationship between ToM performance and basic neurocognitive functions, subsyndromal symptom severity, and illness burden. Twenty-nine clinically stable outpatients with bipolar disorder and 29 healthy comparison subjects completed a measure of visual cognitive ToM (Mental State Attribution Task, MSAT), a measure of visual affective ToM (Reading the Mind in the Eyes Test, RMET), and a battery of tests assessing neurocognitive functioning (attention, verbal memory, executive functions, and intelligence).

Patients did not differ significantly from healthy controls for the ToM tasks or any of the neurocognitive measures, suggesting a high level of neurocognitive functioning in the bipolar group. On average, patients were slower than controls to complete the ToM tasks. Within the bipolar group, ToM performance was moderately correlated with attention, verbal memory and reasoning abilities. Performance on the RMET was positively correlated with clinician-rated depressive symptoms with a small effect. Number of years of illness was weakly and negatively correlated with performance on the MSAT. Overall, no moderate or strong correlations were found between ToM performance, subsyndromal depressive or manic symptoms, illness duration, and number of depressive or (hypo)manic episodes. Moderate correlations between ToM performance and age were found for patients but nor for controls.

Our findings suggest preserved visual cognitive and affective ToM abilities in euthymic bipolar patients characterized by a high level of neurocognitive functioning.