Objective: Depression and fatigue are among the most common symptoms of multiple sclerosis (MS). These symptoms frequently co-occur and partially overlap in MS but their underlying biological substrates are unclear. In this study, the relative role of cytokines and hypothalamic-pituitary-adrenal (HPA) axis activity in depression and fatigue were examined in patients with relapsing-remitting MS (RRMS).
Methods: HPA axis function and frequency of stimulated cytokine (interferon γ (IFNγ) and tumour necrosis factor α (TNFα)) producing T cells was measured cross sectionally in 44 female patients with RRMS. All subjects completed a neurological examination, the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) and self-report questionnaires.
Results: 10 patients met diagnostic criteria for major depressive disorder (MDD). MS patients with comorbid MDD showed normal morning but elevated evening salivary cortisol levels, resulting in a flattened slope. While a higher frequency of cytokine producing CD8+ T cells was also seen in MS patients with MDD, these markers were more closely associated with fatigue than depression.
Conclusions: This study supports a role for HPA axis hyperactivity in major depression in MS. In addition, inflammatory and neuroendocrine factors may differentially mediate fatigue and depressive symptoms.