Endocrine and immune substrates of depressive symptoms and fatigue in multiple sclerosis patients with comorbid major depression

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 gamma (IFN gamma) and tumour necrosis factor alpha (TNF alpha)) 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.