It can sometimes seem strange how so much of the country got hooked on opioids within just a few years. Deaths from prescription drugs like oxycodone, hydrocodone, and methadone have more than quadrupled since 1999, according to the CDC. But pain doesn’t seem to be the only culprit: About one-third of Americans have chronic pain, but not all of them take prescription painkillers for it. Of those who do take prescription opioids, not all become addicted.
Several researchers now believe depression, one of the most common medical diagnoses in the U.S., might be one underlying cause that’s driving some patients to seek out prescription opioids and to use them improperly.
People with depression show abnormalities in the body’s release of its own, endogenous, opioid chemicals. Depression tends to exacerbate pain—it makes chronic pain last longer and hurts the recovery process after surgery.
“Depressed people are in a state of alarm,” said Mark Sullivan, a professor of psychiatry at the University of Washington. “They’re fearful, or frozen in place. There’s a heightened sense of threat.” That increased threat sensitivity might also be what heightens sensations of pain.
Not only do people with depression tend to be more pain-sensitive, the effect of opioids can, for some, feel as mood-elevating as an antidepressant.
“Depression is a mixed bag,” Sullivan said. “People can feel sluggish and uninterested, but they can also feel agitated, irritated, and anxious. They feel both unrelaxed and really unmotivated at the same time.”
Opioids might, at least temporarily, feel soothing and sedating. Indeed, several studies have found that buprenorphine, an opioid that is typically used to wean people off of heroin, has some antidepressant properties.
Sullivan and other researchers from Washington and California found in 2012 that depressed people were about twice as likely as non-depressed ones to misuse their painkillers for non-pain symptoms, and depressed individuals were between two and three times more likely to ramp up their own doses of painkillers. Adolescents with depression were also more likely, in one study, to use prescription painkillers for non-medical reasons and to become addicted.
In 2015, a different group of researchers found that depressed people were likely to keep using opioids, even when their pain had subsided and when they were more functional. “If the emotional pain, the depression, is never properly diagnosed or treated, the patient might continue taking the opioid because it’s treating something,” said Jenna Goesling, an assistant professor in the department of anesthesiology at the University of Michigan and an author of that study.
Most recently, a group of Harvard researchers found that mood disorders didn’t increase the likelihood that people would start using opioids, but they nearly doubled the risk that a person already using opioids would continue to use in the long-term.
Finally, prescription opioids can also exacerbate depression, creating a vicious cycle for patients who become dependent on them.
Most opioid abuse starts with people taking medications that weren’t prescribed for them, so some depressed people are simply pilfering a relative or friend’s extra pills. But some unnecessary painkiller prescriptions might start when some patients, fearing stigma, raise their pain symptoms with their doctors, rather than their depression, Sullivan said. “People are treated like innocent victims when they present with pain complaints,” Sullivan said. But depression, wrongly, “feels like more of a personal failing than being in pain.” After all, it’s easier to explain not being able to get out of bed because of a bad back than crushing sadness.
Depression is widely under-diagnosed and untreated, and the shortage of mental-health providers is especially acute in rural areas where the opioid epidemic has hit hardest. Goesling said that we could get closer to untangling the messy connection between pain and depression by improving access to mental health care for people who have chronic pain.
The Republicans’ new health-care plan, which recently passed the House, however, doesn’t do that. Not only does it make major cuts to Medicaid, which in some states pays for half of all addiction treatment cases, it also would allow states to stop forcing insurers to cover mental-health treatment.
If it is driven—at least in part—by depression, opioid abuse can be seen as a cry for help. “People have distress—their life is not working, they’re not sleeping, they’re not functioning,” Sullivan said, “and they want something to make all that better.”
But for depressed patients, heavy-duty painkillers aren’t the right “something.”