LAUSR

OBJECTIVE Youth with chronic orthostatic intolerance (OI) can experience significant physical, social, and academic functional debilitation. Previous studies have indicated associations among symptom severity, psychosocial factors, and functional disability. However, empirically tested models explaining how different medical and psychosocial factors may contribute to functional disability are lacking. The current cross-sectional study aimed to evaluate mediation, moderation, and additive models of the effect of physical symptoms and psychological distress on functional disability. METHODS One hundred and sixty-five youth (13-22 years old) undergoing medical evaluation of chronic OI symptoms completed measures of autonomic dysfunction symptom severity, depressive and anxiety symptoms, and functional disability. Models were evaluated using tests of indirect effects and linear and logistic regression analyses. RESULTS Results supported the mediation and additive effects models for depressive symptoms. Mediation, moderation, and additive models for hypothesized effects of anxiety symptoms were not supported. CONCLUSIONS Results provide preliminary support for models in which OI symptoms affect functional debility via their effects on mood and in which depressive symptoms have unique and additive effects on functioning. Findings lay the foundation for longitudinal and experimental evaluation of biopsychosocial models of functional disability in youth with chronic OI and related conditions. Implications include the importance of a biopsychosocial conceptualization of OI symptoms and debility as a complex interplay of factors rather than as a purely physiological or psychological process.