Opioids may cause short-term improvement in mood but its long-term use imposes risk of new onset of depression, says a new study.Longer duration of use of opioid -- a type of narcotic pain medication derived from opium -- is linked with onset of depression after controlling for pain and daily morphine equivalent doses, the findings showed."Opioid-related new onset of depression is associated with longer duration of use but not dose," wrote Jeffrey Scherrer, associate professor at the Saint Louis University in the US. "Patients and practitioners should be aware that opioid analgesic use of longer than 30 days imposes risk of new onset depression," Scherrer added.The study also calls on clinicians to consider the contribution of opioid use when a depressed mood develops in their patients.Opioid drugs used in the study included codeine, fentanyl, hydrocodone, hydromorphone, levorphanol, meperidine, oxycodone, oxymorphone, morphine and pentazocine.The study was published in the Annals of Family Medicine.