Sleep and circadian rhythm disturbances are common clinical features in people with multiple sclerosis (PwMS) and related demyelinating conditions. Affective symptoms may shape vulnerability to circadian dysregulation. This pilot cross-sectional study examined how affective symptoms and underlying temperamental dispositions relate to circadian rhythm instability in a population of newly diagnosed PwMS and related demyelinating conditions, defined as patients evaluated within 30 days after discharge from the index hospitalization during which the diagnosis was established. Measures included Beck Depression Inventory-II (BDI-II), State-Trait Anxiety Inventory (STAI-Y), Biological Rhythm Interview for Assessment in Neuropsychiatry (BRIAN), Morningness-Eveningness Questionnaire, and brief Temperament Evaluation of Pisa, Memphis, and San Diego. Pearson correlations explored associations among circadian, affective, and temperament dimensions. A multiple linear regression tested independent psychopathological variables associated with BRIAN total scores. In our sample (n = 77; mean age 33 y; 71% women; 81.8% relapsing-remitting MS), clinically relevant depressive symptoms were present in 22%, and state/trait anxiety in 46% and 41% PwMS, respectively. Circadian dysregulation (BRIAN ≥ 40) showed a prevalence of 13.7%. BRIAN scores correlated with BDI-II (r = .68), STAI-Y1/Y2 (r = .55-.60), and depressive/cyclothymic/anxious/irritable temperaments (r = .37-.42). In the regression model (adjusted R2 = .521), depressive symptom severity displayed the strongest association with circadian disruption (β = .562, p < 0.001), with a smaller contribution of depressive temperament (β =-.385, p = 0.017). Both current affective symptoms and underlying temperamental traits may contribute to circadian rhythm instability in MS. Systematic assessment of mood and circadian rhythms may offer a more comprehensive framework for identifying clinically relevant chronobiological disruption in these patients.
