Chronic Pain Overview

Pain is now understood to be a multidimensional experience that is shaped by the interaction of biological processes, psychological factors, and social context.^{1 , 2} Chronic pain is typically defined as pain that persists for longer than 3 months or beyond the expected healing time for an injury, and it is a clinical condition that is distinct from prolonged acute pain.³

The causes of chronic pain vary widely and can result from ongoing conditions (e.g., osteoarthritis, rheumatoid arthritis),⁴ persist after an injury or illness has healed, or occur in the absence of a known cause. Chronic pain can affect a person’s mental health; prolonged pain is associated with depression, anxiety, and post-traumatic stress disorder, all of which can further influence pain perception.³

Chronic pain appears to be more common in women than in men,⁵ in part because some causes of chronic pain, such as endometriosis, occur only in women.⁶ In addition, some types of chronic pain that affect both women and men may be experienced more intensely in women because of increased pain sensitivity.⁷ Biological factors, such as sex hormones and nervous system sensitivity, may play a larger role in pain processing in women than in men, and psychological and social factors can further influence pain persistence and severity.¹ These interacting biopsychosocial factors contribute to differences in pain perception, persistence, and severity.⁸

A growing body of evidence that women and men experience pain differently has important implications for the diagnosis and treatment of chronic pain. Current research increasingly focuses on understanding how sex‑related, biopsychosocial differences influence pain processing and treatment response.⁹ This work has prompted growing interest in personalized approaches to chronic pain management, including greater emphasis on nonopioid and multimodal strategies that better account for biological differences in pain mechanisms and medication response.¹⁰

The NIH Pain Consortium brings together the many NIH Institutes and Centers that engage in pain research. The Consortium’s goal is to support pain-related research initiatives, activities, and strategic planning and to increase the visibility of pain research both inside and outside of NIH. The Consortium collaborates with the National Institute of Neurological Disorders and Stroke (NINDS) to provide guidance on NIH pain research programs.

The NIH Helping to End Addiction Long-Term (HEAL) Initiative remains the largest coordinated U.S. investment in pain research. HEAL-funded research has increasingly focused on understanding how biological underpinnings of pain interact with psychological and social factors, aligning closely with biopsychosocial models. HEAL studies frequently analyze study outcomes by sex, including hormonal influences and differential pain trajectories for women and men.