Brainstem Raphe Echogenicity and Insomnia in Type 2 Diabetes: An Exploratory Cross-Sectional Study

Background: Type 2 diabetes mellitus (T2DM) is associated with increased vulnerability to depression and other affective disturbances, potentially mediated by neurobiological alterations in the serotonergic brainstem raphe nuclei. This study examined whether raphe hypoechogenicity, assessed by transcranial sonography, is associated with depressive, anxiety, and sleep-related symptoms in individuals with T2DM, and whether such alterations are linked to diabetes-related complications. Methods: This cross-sectional study included 230 participants with T2DM and non-diabetic controls. Raphe echogenicity was assessed using transcranial sonography (TCS), and mental health outcomes were measured with the Patient Health Questionnaire 9 (PHQ-9) and the Emotional Well-Being Questionnaire (EWQ). To address demographic imbalance, analyses were repeated in a propensity score–adjusted subsample (n = 89). Results: Raphe hypoechogenicity was associated with higher insomnia scores (EWQ6; β = 0.67, p = 0.01); however, this association was attenuated to non-significance after adjustment for sleep medication use and did not survive correction for multiple comparisons, and no associations were observed with PHQ-9 or other EWQ subscales. The participants with hypoechogenic raphe also exhibited a higher prevalence of other diabetes-related complications (32% vs. 7%, p = 0.03). Conclusions: In this exploratory cross-sectional sample, reduced raphe echogenicity was not associated with overall depressive or anxiety symptom severity, but was associated with higher self-reported sleep-related symptom burden. However, this association was not robust to adjustment for sleep medication use or to correction for multiple comparisons. These findings are hypothesis-generating and require replication in larger, longitudinal and medication-naive cohorts using standardized sleep instruments.