Individual differences in the day-to-day experience of chronic pain: a prospective daily study of rheumatoid arthritis patients.

Explored the distribution and temporal patterning of daily pain reported by 47 patients with rheumatoid arthritis (RA) for 75 consecutive days. Approximately half the pain series were significantly positively skewed, trended significantly across the recording period, or both. One fourth of the sample had relatively painful "outlier" days that clustered together. Most series displayed a significant autocorrelation in pain intensity across successive days even when the series were detrended. Patients with more active disease had pain that was more intense but more predictable from day to day and reported fewer painful outlying days and briefer episodes of atypically severe pain. Patients describing themselves as more depressed on the Center for Epidemiological Stress Depression Scale also reported more intense pain across the recording period, independent of their level of disease activity and disability. Implications for daily process studies of RA pain are discussed.