Chronic pain is a widespread problem. It affects millions of Americans, hindering many from working, attending school or socializing.

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The scope and severity of such pain can shift widely by individual. And, because causes and conditions vary, there is no uniform treatment to help provide comfort.

It might also leave patients feeling hopeless: One nationwide survey found that two-thirds of people with chronic pain expect to live with it for the rest of their lives.

"If all chronic pain conditions were lumped together and considered to be a single disease, as many pain researchers view the problem, this aggregate would be the most common, disabling and expensive health problem in the world," says Daniel Clauw, M.D., director of Michigan Medicine's Chronic Pain and Fatigue Research Center.

Here's how prevalent chronic pain is in the United States:

Sources: American Academy of Pain Medicine, The National Academies of Sciences, Engineering and Medicine, Institute of Medicine of The National Academies, National Center for Complementary and Integrative Health, National Institute of Neurological Disorders and Stroke