ETD

• bipolar disorder
• circardian rhythms
• interoception
• interoceptive sensibility

Background: Bipolar Disorder is a severe and chronic psychiatric condition characterized by the recurrence of manic, hypomanic, and/or major depressive episodes. Disruptions in circadian rhythms are considered to be a core feature of Bipolar Disorder; these often manifest as irregular sleep-wake cycles and as a tendency towards an evening chronotype.
At the same time, increasing evidence indicates that individuals with Bipolar Disorder exhibit alterations in interoceptive processing. Interoception represents the ability to perceive, interpret, and regulate internal bodily signals, and plays a crucial role in maintaining homeostatic balance and emotional regulation.
Building on this framework, the instability of biological rhythms observed in individuals with Bipolar Disorder may not simply reflect an external desynchronization but could instead originate from an altered integration of internal bodily states. Consequently, the aim of this thesis is to explore the potential mediating role of interoceptive sensibility in circadian rhythm disruption, using Bipolar Disorder as a clinical model.
Methods: The study population included 44 individuals, aged from 18 to 65, with a diagnosis of Bipolar II Disorder in depressive phase, along with a healthy control group comprising a total of 31 participants.
Participants underwent psychometric assessment, including the Multidimensional Assessment of Interoceptive Awareness (MAIA) to investigate interoceptive sensibility, and the Biological Rhythms Interview of Assessment in Neuropsychiatry (BRIAN) to measure the severity of disruptions of circadian rhythms.
Results: Compared to individuals in the control group, patients with Bipolar Disorder exhibited significantly higher circadian rhythm dysregulation (p = .002) and lower interoceptive sensibility (p < .001), particularly when referring to higher-order components such as Self-Regulation and Trusting. Mediation analysis showed that reduced Self-Regulation significantly mediated the relationship between Bipolar Disorder and circadian rhythm dysregulation (β = -4.64, 95% CI [-9.13; -1.57]).
Discussion: The results indicate that individuals with Bipolar Disorder show a significantly impaired rhythmicity of circadian rhythms, as measured by the BRIAN, with the most pronounced disruptions being in the subscales of Activities and Sleep. Whereas through the analysis of the MAIA scores, a corresponding deficit in the overall level of interoceptive sensibility was revealed within the same patient cohort. Said impairment did not manifest as a generalized reduction in bodily sensibility levels but was instead specific to the more cognitively demanding higher-order processes of interoception. The most significant deficits were shown to be in the capacity to Trust internal bodily signals and to use these signals for Self-Regulation.
Furthermore, mediation analyses suggest that the inability to effectively use internal bodily signals for self-regulation may contribute as a key factor to the instability of biological rhythms, which is typically observed in patients with Bipolar Disorder.
Taken together, these findings support the hypothesis that circadian dysregulation in bipolar disorder may originate, at least in part, from altered interoceptive processing.
From a clinical perspective, these results suggest that interventions and treatments that are aimed at improving an individual’s ability to use internal bodily signals for Self-Regulation could represent a new strategy to help mitigate the level of instability of biological rhythms, which is a well-established core feature of Bipolar Disorder.