People who suffer from depression are much more likely to be prescribed powerful opioid painkillers like morphine and codeine and to stay on the drugs long-term, new research shows.

What’s more, they are often prescribed these more potent medications at higher doses, Dr. Jennifer Brennan Braden of the University of Washington in Seattle and her colleagues found.

Because depressed people may also be at greater risk of abusing or becoming addicted to these painkillers, the researchers say more research is needed to understand the safety of prescribing opioids in depressed patients, and whether it’s effective.

Opioids are increasingly being prescribed to treat chronic pain that is not related to cancer. To investigate patterns in prescribing these drugs, the researchers looked at records from two large health plans for 1997 through 2005.

Most commonly, people were prescribed opioids to treat back pain, pain in the arms or legs, or pain from arthritis. Depressed people were two to four times more likely to be prescribed opioids for non-cancer pain, Braden and her team found.

They were also prescribed higher daily doses and more days’ supply.

For example, in 2005, 25 percent of depressed patients in one health plan had a long-term opioid prescription, compared to 9 percent of non-depressed patients in the same plan.

The average dose for depressed patients in the same plan was 54 milligrams, compared to 45 milligrams for non-depressed patients; in the other plan, average doses were 65 milligrams for depressed patients and 48 milligrams for non-depressed patients.

The researchers also found that depressed individuals were more likely to be prescribed longer-acting drugs, and more likely to also have been taking sedative-hypnotics (sleeping pills and tranquilizers like Valium and Ativan). Combining sedative-hypnotics with opioids, especially if they are used along with alcohol or other sedatives, increases the risk of overdose, Braden and her team note.

Depressed patients may be more likely to request opioids, the researchers suggest, while doctors may be more likely to prescribe the drugs “based on observed or reported distress” seen in a person with depression. It’s also possible, Braden and her colleagues add, that depressed people may have higher levels of pain that don’t respond well to standard treatments.

While the findings can’t show if the prescribing patterns they observed were appropriate, the researchers say individuals with depression “represent a potentially high-risk group for adverse outcomes of opioid use.”

SOURCE: General Hospital Psychiatry, November-December 2009.