Background Juvenile arthritis is characterised by periods of flare and relative quiescence. Periods of flare are characterised by increased disease activity and worsening symptoms. While the cause of disease flares is unclear, multiple possible triggers have been proposed including infection, trauma, psychosocial stress, and mood.

Objectives The purpose of this study was to examine the relationship of daily mood and daily stressful events to disease symptoms in children with rheumatic disease.

Methods Twenty-four school-aged children (15 girls, 9 boys, mean age 12.4 years) with polyarticular arthritis completed a daily booklet over a two-month period, yielding 1355 total observations. The daily booklet included measures of daily symptoms, function, mood, and stressful events. In addition, we obtained biological measures of disease activity, as well as salivary cortisol levels three times daily. Data were analysed using multi-level random effects modelling in order to take into account both sources of variation in the data set, within-person and between-person. In addition, multilevel models use the number of observations or days rather than the number of participants as the unit of analysis, thus increasing the statistical power.

Results The models indicated that on a day-to-day basis, worse mood and more stressful events were significantly related to increases in daily pain (p < . 0001 and p < . 02), fatigue (p < . 0001 and p < . 02), and increased interference in social activities (p < . 0001 and p < . 001). Worse mood was also related to increases in daily stiffness (p < . 0001) and to coping, including the ability to control (p < . 0001) and decrease pain (p < . 0001).

Conclusion Our data show that day to day fluctuations in mood and stressful events are related to the daily symptoms of children with juvenile polyarticular arthritis and may play a role in the pathogenesis of disease flares. Therefore, interventions aimed at improving mood and stress coping may improve the health status of children with arthritis.