Chronic Pain: Pain sometimes evolves into a poorly understood condition known as chronic pain syndrome. Unlike acute pain, this condition doesn’t go away after the injury or illness has healed. It’s marked by pain that lasts longer than six months and is often accompanied by anger, depression, anxiety, loss of sexual desire, and disability. Chronic pain syndrome may occur along with other conditions that involve long-term pain, including certain cancers, stroke, fibromyalgia, chronic fatigue syndrome, endometriosis, and inflammatory bowel disease. Experts don’t yet understand how these conditions are related. However, research suggests that psychological problems alone are not the sole cause of chronic pain syndrome. Chronic pain appears to be linked to abnormalities in the interactions among the hypothalamus, pituitary, and adrenal glands and the nervous system. Abnormalities in this stress axis, which controls our reactions to stress, injury, and trauma, may be the reason certain people experience pain differently.