Brain & Behaviour

Neurobiological Mechanism of Placebo


The placebo effect is one of the most mysterious and least understood phenomena of human psychology and physiology. The “PLACEBO” term has a Latin origin that means “I Shall Please.” It was used in eighteen century for the very first time to test a medicine that actually relieved a patient from pain rather than giving real treatment. Pain relief is one of the most common application of placebo effect. The placebo response has achieved wide recognition in neuroscience as well.

What is Placebo?

A placebo is basically an ordinary substance or virtual treatment that is similar to a real treatment. The patient under examination is given inactive ingredients. The recovery depends upon the combination of suggestions, expectations and observational cues. All these factors trigger brain and enhance expectations of recovery. When patients are told that they are being given active ingredients- their brain produces dopamine, a chemical strongly associated with satisfaction and pleasure. The neurological effects of placebo are evident for experiencing pleasurable experiences.

Placebo: A Psychobiological Phenomena

A placebo effect is actually a psychobiological phenomenon taking place in the human brain right after giving an inert substance or a physical treatment along with verbal suggestions. So the entire credit cannot be attributed only to the inert ingredients. The relief is because of the psychosocial context. One more term “Nocebo” is frequently used along with placebo. The nocebo effect is the reverse of placebo effect. Negative expectations and suggestions can induce illness as well. Informing a patient about the complication of a suggested treatment might increase the risk of nocebo. An individual feels more pain when he/she expects to receive it.

Examples From historic Events:

One out of three patients report feeling better after being treated with inert substances. Placebo causes biological changes that actually alters the brain activity releasing pleasure hormones. During World War II, Dr.Henry Beecher was treating wounded soldiers. He ran out of pain killer, morphine. He started infusing soldiers with saline solution but continued telling them that they were given morphine for pain relief. Surprisingly, 40% soldiers got effective results. Today, neurobiologist better understand this mechanism that how those soldiers got effective results.

Mechanism Of Placebo: What Happens In Brain?

Jon-Kar Zubieta is a neurobiologist working at the University Of Michigan, used some amazing tactics in order to find out the mechanism of placebo effect occurring in the brain. After extensive research, he highlighted an area of the brain called the nucleus accumbens (NAcc). The interesting fact that actually makes sense is that this part of our brain is accountable for expectancy of reward. The experiments were done with plain saline solution. The PET scans afterwards revealed actual dopamine release from nucleus accumbens.

Amazing facts about placebo:

  1. Hot colored tablets and pills like orange and red work well as stimulants.
  2. Cool colored pills like purple, pink and yellow work best as antidepressant.
  3. Big pills are believed to cure pain more quickly than small ones.
  4. A placebo given for curing pain can be as effective as 8mg of morphine (pain killer).
  5. Placebo given in the form of injection works better than giving oral medicine.
  6. Branded medicine or costly dose shows quick and effective results than cheap ones.
  7. Placebo also works on animals.


Psychological, behavioral and neuroimaging results have made contributions in accepting the placebo response as real and authentic. The major advancement in this area is to create linkages between brain, behavior and bodily responses. Neurologists have studied and examined brain during placebo treatments and pointed out areas that become active and release hormones. In short, placebo is a “real” neurobiological phenomena that deserves neuro clinical implications and medical research. We expect a shift in its process and design of clinical trials with significant implications in the near future.






About the author

Zainub Binte Irfan

An MS degree holder in human resource management. A keen observer that soaks surroundings and then formulate ideas into words. I’m imaginative and I genuinely believe that if you have no raw material then certainly you have nothing to generate with.