ASSOCIATION BETWEEN SUB-THRESHOLD DEPRESSIVE SYMPTOMS AND NO THEORY OF MIND RESPONSES IN BIPOLAR DISORDER
Authors: Tsai *Ying Tsung , Huang Yu-Lien , Lu Tsung-Hua , Chang Wei Hung , Yang Yen Kuang , Chen Po See , Tseng Huai-Hsuan 
Published: February 2025

Abstract

Background
Sub-threshold depressive symptoms play a crucial role in the impaired psychosocial functioning of individuals with bipolar disorder (Van Rheenen &Rossell, 2014). Additionally, social cognitive deficits, particularly in emotion recognition and Theory of Mind, constitute significant determinants of psychosocial impairment in bipolar disorder (Gillissie et al., 2022; Samamé, 2013; Vlad et al., 2018). Previous research has demonstrated that individuals with subclinical depression and major depressive disorder exhibit impaired Theory of Mind abilities (Schreiter, Pijnenborg, &aan het Rot, 2013). However, it remains uncertain whether a similar association between depressive symptoms and social cognition exists in the context of bipolar disorder.

Aims & Objectives
We aimed to investigate the association between sub-threshold mood symptoms and social cognition in individuals with bipolar disorder.

Method
We recruited 29 outpatient individuals diagnosed with bipolar disorder and 44 healthy controls. All participants underwent interviews conducted by certified psychiatrists for the assessment of sub- threshold mood symptoms, utilizing the Hamilton Depression Rating Scale (HDRS) and Young Mania Rating Scale (YMRS). Additionally, participants completed the Movie for the Assessment of Social Cognition- Taiwanese version (MASC-TW) for the evaluation of social cognition. The MASC-TW, validated as a Mandarin equivalent of the MASC (Huang et al., 2023), is a sensitive video-based test designed to assess social cognition (Dziobek et al., 2006).

Results
The bipolar disorder (BD) and healthy control (HC) groups did not exhibit significant differences in terms of age, sex, and education. The BD group demonstrated significantly higher levels of sub- threshold depressive and manic symptoms compared to the HC group (ps &lt;0.002). The BD group displayed a numerical increase in incorrect responses on the MASC-TW compared to the HC group (p = 0.126).
Greater levels of sub-threshold depressive symptoms were associated with fewer correct responses on the MASC-TW in both groups (BD group: r = -.590, p = 0.004; HC group: r = -.335, p = 0.026).
Specifically, in the BD group, higher HDRS scores were linked to a greater frequency of “no Theory of Mind” responses (r = 0.60, p = 0.003), while higher HDRS scores in the HC group were associated with a greater frequency of “excessive Theory of Mind” responses (r = 0.41, p &lt;0.005).

Discussion & Conclusion
Previous studies suggest that social cognitive deficits in bipolar disorder may manifest more subtly compared to schizophrenia. The statistical insignificance of the numerical increase in incorrect responses in the BD group may be attributed to the relatively small sample size. Notably, sub-threshold depressive symptoms were found to correlate with difficulties in mentalizing abilities, whereas manic symptoms did not demonstrate a similar association. Additionally, the types of incorrect responses made by individuals with depressive symptoms may vary across different diagnostic groups. It is important to note that this study is limited by its small sample size and cross-sectional design.
However, gaining a deeper understanding of the distinctive role played by sub-threshold depressive symptoms in social cognitive deficits in bipolar disorder may offer valuable insights for the development of targeted interventions in the future.

References
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