Patients with chronic bipolar disorder show impairments in interpreting literary fiction - A preliminary explorative study with the short story task

Introduction: Theory of mind (ToM) is a crucial skill in navigating and functioning in the social world. Significant ToM impairment was consistently found in bipolar disorder; it can be both a state and trait marker of the disorder. However, most of the ToM tests are not sensitive enough to detect subtle individual differences, which would be necessary for an individualized treatment plan. The Short Story Task (SST) is a new way to sensitively assess individual differences in ToM performance. The aim of the study was to test the feasibility of SST in patients with bipolar disorder. Method: 31 persons (11 male, 20 female) with bipolar I disorder and 31 healthy individuals (15 males and 16 females) as a control group were recruited. SST was used to evaluate ToM performance. The SST uses a Hemingway novel, in which the patient is presented with a realistic social situation, where the motivations of the characters and the underlying relationships of events are not explicitly described. Results: In the explicit mental state reasoning questions the CG (M = 8.06) had significantly higher (p < 0.001) scores than the persons with bipolar I disorder (M = 5.03). There was no ceiling effect for explicit ToM scores in either group. Participants in CG (M = 8.03) also significantly outperformed (p = 0.006) the BG participants (M = 6.55) in the comprehension questions. The spontaneous mental state inference question was performed equally (M = 0.23) in both groups. Group assignment (t = -3.503, p < 0.001), comprehension score (t = 2.864, p = 0.006), and spontaneous mentalization (t = 2.846, p = 0.006) significantly predicted the explicit ToM performance. Conclusions: Overall, we found that the Short Story Task is a promising tool for measuring ToM in patients with bipolar disorder without ceiling effect. Primarily explicit ToM was found to be deficient, which corresponds well with the ToM literature in bipolar disorder. Contrary to our hypothesis we could not detect impairment in spontaneous ToM and found that patients living with bipolar disorder also showed deficits in comprehension. The lack of assessment of neurocognitive skills is a significant limitation of the current study.