Sullivan MD - In this review of prospective cohort, retrospective cohort, and other observational studies, the researcher examined the association between depression and opioid use, abuse, and addiction. Depression was found to be related to slightly more often initiation of opioid therapy and to double risk of transitioning to long-term use, compared with nondepressed patients. In depressed patients vs nondepressed patients, opioid use was seemed to be continued at lower pain intensity levels and higher levels of physical function. The risk of incident, recurrent, and treatment-resistant depression was shown to be increased by long-term opioid therapy in studies that carefully controlled for confounding by indication. Overall, understanding the close and multifaceted relationship of long-term opioid therapy with depression is important to understand this therapy for chronic pain.