Does being defiant and irritable take a toll on physical health? Examining the covariation between symptoms of physical health and oppositional defiance across adolescence to young adulthood.

Methods. Participants (N = 662; 52% female) from the Victoria Healthy Youth Survey (V-HYS) were assessed for ten years across six biennial occasions from ages 12-18 to ages 22-30. A multilevel time -varying covariation model, disaggregating within- and between - person variability, examined whether change in ODS was systematically associated with change in physical health symptoms. Results. On average, individuals with higher ODS reported more physical health symptoms. Moreover, ODS also shared a significant within - person time - varying association with physical health, suggesting that the two symptom domains fluctuated together within - individuals across time, irrespective of between - person differences. Conclusion. This study provides a novel within- and between - person demonstration of the link between ODS and physical health symptoms from youth to young adulthood.