Brain anatomy and personality type may influence susceptibility to the placebo effect.
A placebo is a medical intervention — be it a pill, injection, or sham surgery — that has no therapeutic value.
The placebo effect refers to the real benefits that these inert interventions can have.
The simple act of taking a tablet can make a person feel its benefits.
However, this is not just a psychological phenomenon; it has a biological basis.
As one example, some studies have shown that a placebo can affect blood pressure; a clear physiological response.
In chronic pain trials, for instance, the placebo effect can often be as great as the response to the treatment that is being tested. In actual fact, the response to a placebo can sometimes be larger than the response to conventional treatment.
Placebo as a viable option
Because the standard drugs that are used to treat chronic pain can have significant adverse effects over time, the potential for an inert tablet to benefit some patients is of great interest. One of the difficulties, though, is that not everyone is equally susceptible to the placebo effect.
A recent study set out to probe this problem: could it be possible to predict the size of someone's response to a placebo before they take it? The results were recently published in the journal Nature Communications.
To investigate, scientists at Northwestern University in Illinois studied 60 volunteers with chronic back pain. They split the group into two study arms; one took either the drug or placebo, while another attended the clinic but underwent no treatment.
Each person completed a number of in-depth questionnaires that assessed their personality and the type of pain that they experienced. They also went through four neuroimaging sessions.
As expected, some individuals who took the placebo felt significant pain relief; these participants were then examined further.
The scientists found that those who responded to the placebo had asymmetry in their subcortical limbic system, which is a part of the brain involved in emotion.
Particularly, the investigators found it to be larger on the right side than on the left. These people also had a larger cortical sensory area than those who did not respond to the placebo.
Also, volunteers with a strong placebo response were more emotionally self-aware, mindful of their environment, and sensitive to painful situations.
No need for secrets
Study author A. Vania Apkarian, a professor of physiology at Northwestern University, believes that "[c]linicians who are treating chronic pain patients should seriously consider that some will get as good a response to a sugar pill as any other drug. They should use it and see the outcome. This opens up a whole new field."
Giving a patient a placebo can seem somewhat underhanded, but for those who are sensitive to its powers, this need not be the case.
"You can tell them, 'I'm giving you a drug that has no physiological effect but your brain will respond to it.' You don't need to hide it. There is a biology behind the placebo response."
Prof. A Vania Apkarian
These results could be significant for people with chronic pain and other conditions, and they might also revolutionize the way that some clinical trials are carried out.
The placebo effect has long been a thorn in the side of medical research; knowing exactly what has relieved the symptoms — be it the drug or the placebo effect — can never truly be known.
However, if researchers know which participants are likely to have larger placebo responses, they can screen them out initially, providing more reliable results in the long run.
As Prof. Apkarian explains, "Drug trials would need to recruit fewer people, and identifying the physiological effects would be much easier."
The more we understand about the placebo effect, the closer we get to treating illnesses without the need for toxic chemicals. "It's much better to give someone a nonactive drug rather than an active drug and get the same result," Prof. Apkarian adds.
Although the placebo effect holds a great many mysteries left to solve, the more we understand, the closer we get to treating certain conditions in a much gentler manner.