Around 100 million adults in the United States are affected by chronic pain – pain that lasts for months or years on end. It is one of the country’s most underestimated health problems. The annual cost of managing pain is greater than that of heart disease, cancer and diabetes, and the cost to the economy through decreased productivity reaches hundreds of billions of dollars. Chronic pain’s unremitting presence can lead to a variety of mental-health issues, depression above all, which often