Chronic pain patient may respond to endogenous opioids differently than healthy people.
A recent study showed that both real and sham acupuncture resulted in decreased reports of pain when the patients believed it would work, as well as different brain regions were activated during real versus sham treatment.
Most importantly, the study participants were osteoarthritis patients — patients who were actually dealing with chronic pain.
The trial used real and sham acupuncture coupled with functional magnetic resonance imaging (fMRI) scans to explore the effects of a patient’s expectation that a treatment will alleviate their pain on that treatment’s efficacy.
Randy Gollub, MD, PhD, an associate professor of psychiatry at Harvard Medical School, and her team have done these types of experiments before, but only ever on healthy patients—which may have hidden details.
Some studies, such as a recent one from the University of Michigan, have suggested that chronic pain patients have structural differences in the areas of the brain that are activated during pain modulation, and they may respond to endogenous opioids differently than healthy people do.
“Having the experience of living many, many years with pain may make you think about that differently,” Gollub told MD Magazine. “So, we took a study and we replicated it in a population and then we asked the question, ‘What does this look like in the brain?’”
The study included 42 patients, all suffering from chronic pain due to osteoarthritis. The investigators conditioned the patients using the same protocols they had used in previous studies on healthy patients. They told the patients that they would receive 2 identical heat pain stimuli on each of their forearms. On 1 side, they were told they’d receive a treatment to reduce the pain after the first heat pain stimulus.
In reality, on the “treated” forearm, the second stimulus was a lower temperature than the first. On the untreated side, they received identical stimuli. This enhanced the feeling of analgesia, helping to convince the patients that the treatment was effective.
Each patient participated in 2 behavioral testing sessions which included neuropsychological assessments, and 1 fMRI scanning session. Each session was separated by 3 to 10 days.
The researchers found that behaviorally, both healthy patients in previous studies and chronic pain patients in the current study responded the same way to treatment. Most reported decreased pain for both real and sham acupuncture.
Interestingly, the brain scans showed slight differences in the areas that were processing these sensations.
Gollub explained that this study only included osteoarthritis patients and that she compared their data to previous studies on healthy patients, so future studies will need to include healthy, matched controls.
“That the time that [doctors] spend and the relationship that they build with [their patients], and the expectation that they create, that they're there to help their patient feel less pain and be more comfortable, is an important ingredient in their therapeutic armamentarium,” Gollub said. “We can tell from people's brain scans that their belief in the treatment has an impact on how they experience pain.”
The study, “A Functional neuroimaging study of expectancy effects on pain response in patients with knee osteoarthritis,” was published in the Journal of Pain.
This article was originally published by MD Magazine.