P 133 Differentiating hypo- and hyperaroused fatigue in major depression and in the context of organic diseases

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Introduction Fatigue is a core symptom in patients with major depressive disorder (MDD), and a common symptom in organic diseases involving inflammatory and immunological processes. From a clinical perspective, fatigue in depression is a state with high inner tension and prolonged sleep onset latencies, whereas fatigue in the context of organic diseases describes an anergic state with excessive sleepiness and short sleep latencies. Given that these two states are diametrically opposed in the arousal dimension, it has been proposed to differentiate two subtypes of fatigue ( Hegerl et al., 2013 , Hegerl and Ulke, 2016 ): hyperaroused fatigue (typical for depression) and hypoaroused fatigue (typical in the context of organic diseases). Due to the striking heterogeneity of MDD and frequent occurrence of depressive symptoms in organic diseases, we sought to examine whether both fatigue subtypes can be found within a sample of depressed patients (study 1) and within a sample of subjects with inflammatory-immunological diseases and cancer (study 2). In the first study, we hypothesized that in MDD fatigue with unstable arousal regulation is associated with higher sleepiness scores and more atypical symptoms (e.g. short sleep onset latency) than fatigue with stable arousal regulation. In the second study, we hypothesized that in the context of organic diseases fatigue with stable arousal regulation is associated with higher depression and lower sleepiness scores than fatigue with labile arousal regulation. Methods Sample Study 1: MDD-Patients with clinically relevant fatigue (N = 102). Sample Study 2: Subjects with clinically relevant fatigue in the context of inflammatory-immunological diseases and cancer (N = 127). Arousal regulation was assessed based on 20-min resting-EEG using automatic EEG-vigilance stage classification with the Vigilance Algorithm Leipzig (VIGALL 2.1). Subjects were separated into groups according to their arousal regulation. Results Study 1: According to our hypothesis, fatigue subtypes in the context of MDD differ in regard to daytime sleepiness (ESS: p Conclusions An unstable arousal regulation in MDD-Patients with clinically relevant fatigue could influence the treatment strategy. Stable arousal regulation in persons with clinically relevant fatigue in the context of organic diseases can be an indication of a comorbid depression, which has to be treated according to guidelines.