Mind Over Matter: How Placebo Treatments Can Reduce Real Pain

Placebos, the ubiquitous sugar pills of old, are usually employed in drug trials to determine the effectiveness of a medication. Comparing the responses of both the medication and a placebo allows for the measurement of the efficacy of the treatment. However, in some cases, the placebo actually can have an effect, as is the case in a recent trial where the placebo actually reduced pain signaling in their spinal cord.

Past studies have shown that, inexplicabley, placebos can actually have a positive effect. This new study goes further and suggests that the pain-related placebo effect could work by tapping into the pain-suppressing system that is already in place in the body, one that starts in the brain and then relays down to the spinal cord. Scientists know that when people experience a decrease in their pain from a placebo treatment, certain compounds, called endorphins, are released into their brains. However, they still don’t know exactly how the release of these compounds leads to pain reduction.

One idea is that the endorphins will allow certain parts of the brain to “communicate with an evolutionarily preserved system in the brain stem,” one that will control the pain by inhibiting neural activity in the spinal cord, stated Falk Eippert, who is a researcher from the Department of Systems Neuroscience at the University Medical Center Hamburg-Eppendorf in Hamburg, Germany.

Eippert and his research team tested this hypothesis on a group of 15 volunteers. The study subjects were told they would receive painful heat stimulation on their forearm, and during this simulation, their arms would be treated with one of two creams, one which was an active, pain-reliving cream (lidocaine cream), and the other which was the placebo cream used as the inactive control. In truth, neither one of the creams was active and was not designed in any way to reduce pain.

Firs, the team applied the full heat stimulation to the forearms of the subjects that had been treated with the control cream. Next, they tested the so-called “lidocaine” cream. In reality, the research team reduced the heat temperature so the subjects would feel less pain. This was a trick designed to make the volunteers think that the “lidocaine” cream actually had an effect on the pain. Eippert said, “We wanted to induce a belief in the effectiveness of this treatment, the cream, although it doesn’t have an effectiveness, per se.”

Then, the team ran the heat-stimulation again, but this time, they did not reduce the temperature during the “lidocaine” treatment. During this heat stimulation experiment, the team also studied the volunteers with functional magnetic resonance imaging (fMRI) to observe their spinal cord response. The fMRI images show the amount of oxygen in the blood, which is considered an indirect measure of the spinal cord’s neural activity.

When the volunteers were given the control cream, they reported they had a lot of pain, and showed strong activity in their pain cord. However, when the volunteers received the so-called “lidocaine” cream, which they thought was the real treatment but was in fact a placebo, they reported to have less pain and showed less activity in their spinal cord. This suggests that “there must be some inhibition [coming] from the brain,” Eippert stated.

The research team believes that the placebo effect works by recruiting the ancient pain-suppressing system. Eippert said, “What we can now show is that, in humans, this system is brought into play by psychological factors such as expectation of pain relief under placebo. It’s not just altered reporting behavior, it’s a very deeply rooted effect.” This could in fact be something very profound.

With only 15 volunteers, this study might seem a little small, but it is in fact a good size for an imaging study, which often utilizes 10 to 20 subjects, stated Eippert. He also noted that the placebo is very robust, so you really do not need too many people to study it. A study that looks at a smaller behavioral effect might need more subjects.

The data from the study was also analyzed in a way that accounted for the small size of the study. Eippert said,” The kind of statistics that we’re using are explicitly taking into account how many subjects we had.” Their results showed that the reduction of the activity in the spinal cord in response to the placebo treatment was statistically significant.