Depression, Anxiety May Reduce Effectiveness of Opioids for Back Pain

University of Pittsburgh Medical Center

Chronic physical pain and mental anguish are inextricably linked. For those experiencing long-term pain, the constant physical discomfort combined with the inability to go to work or carry out other daily routines can lead to the development of symptoms of depression or anxiety. Similarly, for many people dealing with depression, there is a greater risk of short-term pain becoming chronic.

While there has been a lot of research into the relationship between pain and mental disorders, less is known about how a patient’s mental state may influence his or her response to opioid therapy—a common but potentially risky pain medication given its addictive properties.

Ajay Wasan, M.D., a professor of psychiatry and anesthesiology at the University of Pittsburgh School of Medicine, recently led a study that provided some of the first prospective data on how chronic pain patients (those experiencing pain for more than 12 weeks) with depression or anxiety respond to opioid treatment. His team’s work was published July 3 in Anesthesiology.

For the study, the researchers enrolled 81 chronic lower back pain patients with either low, moderate, or high depressive or anxiety symptoms and monitored their use of either morphine or oxycodone therapy over a six-month period. About 75 percent of the patients in the study developed depression as a result of their pain, but there were also those with preexisting issues.

All patients also underwent physical exams and MRI scans to confirm that the presence of damaged discs contributed to their pain.

A total of 24 participants with high depression or anxiety symptoms and 24 with low symptoms completed the study; seven participants in the moderate group also completed the trial, though the small size of this group made statistical analysis difficult.

The patients with high depression or anxiety symptoms found much less relief from the opioids, reporting about a 21 percent improvement in back pain (as self-reported using a daily electronic diary) compared with a 39 percent improvement reported by the low symptom group. This difference occurred despite the high anxiety and depression symptom group receiving a higher average daily dose of painkillers.

These patients also showed higher levels of opioid abuse (39 percent versus 8 percent) and more frequent and intense side effects from the medication compared with patients with low levels of depression and anxiety.

“This is a small prospective study, but I think it’s also definitive, when you consider how it fits in well with all the other data we have on chronic pain and depression,” Wasan told Psychiatric News. “And it really suggests that anyone diagnosed with chronic pain should be screened for depression and anxiety as soon as possible and before prescribing any opioids.

“At the same time, psychiatrists should be more proactive with their patients as well and not dismiss or undervalue any complaints related to pain,” he said. “The pain they are reporting is likely very real.”

Wasan did not suggest that opioids be prohibited in people with depression, but did note that there are likely better options. Serotonin-norepinephrine reuptake inhibitors (SNRIs), for example, are considered effective frontline treatments for both pain and depression and might be a more appropriate choice, he said.

In this study, all the participants did report improvements in their mood symptoms by the conclusion, with the high depression group reporting the highest gains of about 31 percent improvement. However, this result was still lower than the 50 percent mood improvement typically used as the cutoff of successful treatment.

“Whatever the exact route, the key message is that we want to treat the depression or anxiety in patients experiencing pain right away, which will make opioids safer and more effective if they are needed.

“It may even be possible that by being attentive and intervening early on, we can prevent the transitioning of acute pain into chronic pain,” said Wasan, who is hoping to answer that very question in one of his upcoming clinical studies.

It’s a critical question to address, as chronic back pain is a tremendous burden in the United States. According to the National Institute of Neurological Disorders and Stroke, about 80 percent of adults will experience low back pain at some point in their lives, and one in five of these cases will become chronic. ■