Chronic pain syndromes, mechanisms, and current treatments.

Although acute pain is a physiological response warning the human body of possible harm, chronic pain can be a pathological state associated with various diseases or a disease in itself. In the United States alone, around one-third of the population has experienced a chronic pain condition and annual cost to the society is in the range of 500-600 billion dollars.(1) It should be noted that if at all this is a very modest estimate, it surpasses the costs associated with cancer, heart disease, and diabetes combined.(1) Unfortunately, despite these humongous costs, the treatment of chronic pain is inadequate.(1) Chronic pain affects individuals in a variety of forms, and below we highlight some of the most common chronic pain conditions seen in a pain clinic. Most of these disorders are difficult to treat and typically require multimodal therapy including pharmacotherapy, behavioral modification, and targeted interventions. We have summarized the scope of each disorder, clinical features, proposed mechanisms, and current therapies for them (Table 1).