Abstract
Emerging evidence suggests that mental fatigue is a central component of the cognitive and clinical characteristics of stress-related exhaustion disorder (ED). Yet, the underlying mechanisms of mental fatigue in this patient group are poorly understood. The aim of this study was to investigate cortical and subcortical structural neural correlates of mental fatigue in patients with ED, and to explore the association between mental fatigue and cognitive functioning. Fifty-five patients with clinical ED diagnosis underwent magnetic resonance imaging. Mental fatigue was assessed using the Concentration subscale from the Checklist Individual Strength. Patients with high levels of mental fatigue (n = 30) had smaller caudate and putamen volumes compared to patients with low-moderate levels of mental fatigue (n = 25). No statistically significant differences in cortical thickness were observed between the groups. Mediation analysis showed that mental fatigue mediated the relationship between caudate volume and working memory; specifically, smaller caudate volume was associated with higher level of mental fatigue and mental fatigue was positively associated with working memory performance. Our findings demonstrate that the structural integrity of the striatum is of relevance for the subjective perception of mental fatigue in ED, while also highlighting the complex relationship between mental fatigue, cognitive performance and its neural underpinnings.
Highlights
Stress-related exhaustion disorder (ED) is a clinical condition characterized by psychological and physical symptoms of exhaustion developed in response to long-term psychosocial stress (Grossi et al, 2015)
No statistically significant difference in activity levels or reduced motivation was found between the groups, nor were there any statistically significant differences between the groups in executive function or working memory performance (Cohen’s d = 0.32 and 0.23 respectively, favoring the high mental fatigue group)
Results showed a negative correlation between Checklist Individual Strength (CIS) Concentration score and caudate volumes, indicating that smaller caudate volumes were associated with higher levels of mental fatigue (r = −0.31, p = 0.03, Table 3)
Summary
Stress-related exhaustion disorder (ED) is a clinical condition characterized by psychological and physical symptoms of exhaustion developed in response to long-term psychosocial stress (Grossi et al, 2015). In stress-related ED, fatigue is a central clinical characteristic; a significant lack of psychological energy is part of the diagnostic criteria (Grossi et al, 2015), patients report high levels of fatigue (van Dam et al, 2011), and both physical and mental fatigue are described as residual symptoms by a large proportion of patients several years after treatment (Glise et al, 2020; Stenlund et al, 2012). Krabbe et al (2017) found that, in conjunction with impaired performance on executive function and complex attention tasks, patients with ED experienced a marked increase in mental tiredness during and after cognitive testing. In a study focusing on patients with clinical burnout, Oosterholt et al (2014) demonstrated that despite showing a relatively mild cognitive deficit, patients perceived performing the cognitive tests as effortful and fatiguing. Despite the potential clinical relevance of mental fatigue in ED, the phenomenon has not been well described, and little is known about its underlying mechanisms
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