Mediators and Moderators of Stress - Fatigue and Psychological Distress - Fatigue Relationships in a Non-Clinical Sample

Objective: Stress, psychological distress and fatigue are frequently co-morbid experiences, but the nature of any temporal and/or causal relationships is unclear. This study examined possible mediators and moderators of the stress/psychological distress - fatigue relationship in a non-clinical sample. Methods: A questionnaire assessed stress (i.e., stressful life-events, perceived stress), psychological distress (i.e., state and trait anxiety, depression), sleep quality, social support (i.e., number, quality), illness symptoms and fatigue in 97 female and 40 male university students, aged 18-63 years. Results: Regression models indicated that high perceived stress and state-anxiety, poor sleep quality and general illness symptoms predicted 48% of the variance in fatigue severity. Poor sleep quality and gastrointestinal (GIT) symptoms partly mediated between stress and fatigue, and poor sleep quality partly mediated between psychological distress and fatigue. Social support quality moderated the stress-fatigue relationship. Conclusions: Stress and psychological distress may contribute to fatigue in healthy adults by first impairing sleep quality and/or increasing vulnerability to infection, which may then directly induce fatigue symptoms.