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The unconscious mind plays a key role within the ‘placebo effect’, scientific study has found, allowing them to identify a novel mechanism that helps explain the strength of placebos and nocebos.

The new finding shows that the ‘placebo effect’ can be activated beyond conscious awareness, and supply an explanation for how patients can display clinical improvement even when they receive treatments devoid of ingredients or of known therapeutic efficacy. The research was published online in the Proceedings of the Nas (PNAS).

“Within this study, we used a singular experimental design and located that placebo and nocebo [negative placebo] effects depend on brain mechanisms that aren’t determined by cognitive awareness,” explains Karin Jensen, PhD, of the Department of Psychiatry and also the Martinos Center for Biomedical Imaging at Massachusetts General Hospital (MGH) and also the Enter in Placebo Studies (PiPS) at Beth Israel Deaconess Medical Center/Harvard Medical School. “Of your life a placebo or nocebo response even when he or she is unacquainted with any suggestion of improvement or anticipation of getting worse.”

Scientists have long thought that the placebo effect was related to conscious beliefs or thoughts, which when given an inert pill or therapy, patients get better simply because they have the expectation that they’ll improve. Or perhaps in the situation of nocebos, they worsen because they anticipate that they will worsen.

Recently, though, scientists have recognized that people’s expectation of reward or threat is learned quickly and automatically without needing to consciously register the idea in their brains. Neuroimaging studies from the mind have suggested that certain structures, such as the striatum and also the amygdala, can process incoming stimuli before they reach conscious awareness, and, consequently, may mediate non-conscious effects on human cognition and behavior.

The scientists set out to see whether placebo and nocebo responses might be activated outside of a person’s conscious awareness, even if she or he has no expectation of either improving or declining.

Most people realize that a placebo is an inert treatment which makes the patient or test subject feel good with the power of suggestion. A nocebo works the same way, suggestion and conditioning, but it creates unwanted effects.

According towards the Harvard Medical School’s Health Publications, “A placebo makes patients feel better for reasons unrelated to the specific healing properties of the treatment. A nocebo makes patients feel worse (or does other harm) in the same manner. Common symptoms are drowsiness, headache, mild dizziness, difficulty concentrating, and stomach upset.” One particualr nocebo is a study where volunteers were advised that the mild electrical current would be passed through their heads and it might cause headaches. No current was really passed, but two-thirds of the participants developed headaches.

The research team, including scientists from Plymouth University and also the Karolinska Institute, studied 40 healthy volunteers (24 female; 16 male, median age 23). Two experiments were conducted: Within the first, researchers administered heat stimulation to participants’ arms while simultaneously showing them images of male human faces on a computer screen. The heat stimulation stayed exactly the same throughout, but the faces shown displayed two responses: one related to low pain stimulations and something with high pain.

Participants were then inspired to rate their pain experience on a scale of 0 to 100, with 0 being pain free and 100 to be the worst pain imaginable. As predicted, the pain ratings correlated using the previously learned associations, having a pain rating of 19 when the subjects saw the reduced pain face as the high pain face led to subjects’ mean reports of 53 around the pain scale (nocebo effect).

In the second experiment, the participants were given exactly the same level of heat stimulation while the same faces were flashed on a screen too quickly for conscious recognition. The participants again rated their pain, and despite a lack of consciously recognizable cues, the participants reported a mean pain rating of 25 in reaction to the low pain face (‘placebo effect’) and a mean pain rating of 44 in response towards the high pain face (nocebo response) while they did not consciously recognize the faces on the screen.

“Such a mechanism would certainly be anticipated to be more automatic and fundamental to our behavior compared to deliberate judgments and expectations,” explains Jian Kong of MGH and the PiPS. “Most significant, this research supplies a unique model that enables us to further investigate placebo and nocebo mechanisms by utilizing tools such as neuroimaging.”

As PiPS Director Ted Kaptchuk notes, “It’s not what patients think will happen [that influences outcomes] it’s what the nonconscious mind anticipates despite any conscious thoughts. This mechanism is automatic, fast and powerful, and doesn’t rely on deliberation and judgment. These findings open a completely new door towards understanding placebos and also the ritual of medicine.”