Affective instability in patients with chronic pain: a diary approach

Affective instability, conceptualized as fluctuations in mood over time, has been related to ill-health and psychopathology. In this study we examined the role of affective instability upon daily pain outcomes in 70 chronic pain patients (Mage = 49.7 years; 46 females) using an end-of-day diary. During a baseline phase, patients completed self-reported questionnaires of pain severity, pain duration, disability, depression and anxiety. During a subsequent diary phase, patients filled out an electronic end-of-day diary over 14 consecutive days assessing daily levels of pain severity, disability, cognitive complaints, negative affect (NA) and positive affect (PA). Affective instability was operationalized as the mean square of successive differences (MSSD) in daily mood (separately for NA and PA), which takes into account the size of affective changes over consecutive days. Results indicated that NA instability was positively associated with daily disability, beyond the effects of daily pain severity. Furthermore, NA instability moderated the relationship between daily pain severity and daily disability and the relationship between daily pain severity and daily cognitive complaints. PA instability, however showed to be unrelated to all outcomes. Current findings extend previous results and reveal the putative role of affective instability upon pain-related outcomes and may yield important clinical implications. Indeed, they suggest that targeting NA instability by improving emotion regulation skills may be a strategy to diminish disability and cognitive complaints in patients with chronic pain.