Running head: FIBROMYALGIA AND POSITIVE AFFECT REGULATION Fibromyalgia: Evidence for Deficits in Positive Affect Regulation

Objective: Fibromyalgia (FMS) is characterized by chronic pain, high psychiatric comorbidity, and the absence of observable pathology. Our objective was to examine positive and negative affective indices, both at the trait and contextual levels, in FMS compared to a chronic pain control group, osteoarthritis (OA). Methods: The sample consisted of 126 female FMS (87) and OA (39) patients from the community. Participants answered a self-report questionnaire assessing demographic and personality variables and were interviewed regarding average pain, affect, anxiety, and depression. Participants were then interviewed weekly for up to 12 weeks regarding pain, affect, fatigue, perceived interpersonal stress (IS), and positive interpersonal events (PE). Results: FMS participants reported lower levels of positive affect (p < .01) and extraversion (p < .01) than OA participants. There were no significant differences between groups in negative affect, depression, anxiety, or neuroticism after controlling for age and average pain. At the weekly level, FMS participants reported lower levels of positive affect (p < .01), but not negative affect. Furthermore, during weeks of elevated IS, FMS participants evidenced steeper declines in positive affect than OA participants (p = .01). Conclusions: Despite the predominance of literature focusing on psychological disturbance in FMS, these analyses identified dysfunctional positive affect regulation as a key feature of FMS. FMS status was uniquely characterized by lower levels of positive affect, especially during stressful weeks. These findings challenge current Fibromyalgia: Evidence For Deficits 2 conceptualizations of FMS and point to new directions for interventions that focus on improving positive affective resources, especially during times of stress.