Goal: To test the biological consequences of negative expectations, achieved via an active 10-minute negative cognitive perseveration on a personally relevant stressor: future worsening of one's chronic pain condition. Biological stress response will be measured via heart rate (HR), blood pressure (BP) and serum cortisol. Impact of negative cognition on inflammation will be measured using interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) as biomarkers of immune function, controlling for depression and pain catastrophizing. This study aims to inform the understanding of pain mechanisms.