Chronic pain is pain that lasts a long time. In medicine, the distinction between acute and chronic pain is sometimes determined by an arbitrary interval of time since onset; the two most commonly used markers being 3 months and 6 months since onset, though some theorists and researchers have placed the transition from acute to chronic pain at 12 months. Others apply acute to pain that lasts less than 30 days, chronic to pain of more than six months duration, and subacute to pain that lasts from one to six months. A popular alternative definition of chronic pain, involving no arbitrarily fixed duration, is “pain that extends beyond the expected period of healing”. Epidemiological studies have found that 10.1% to 55.2% of people in various countries have chronic pain.
Chronic pain may originate in the body, or in the brain or spinal cord.
Severe chronic pain is associated with increased 10 year mortality, particularly from heart disease and respiratory disease. People with chronic pain tend to have higher rates of depression, anxiety, and sleep disturbances; these are correlations and it is often not clear which factor causes another. Chronic pain may contribute to decreased physical activity due to fear of exacerbating pain, often resulting in weight gain. Pain intensity, pain control, and resiliency to pain are influenced by different levels and types of social support that a person with chronic pain receives.