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13 April 2015

Can Positive-Thinking Heal You? The Science Behind the Placebo Effect

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The Power of a Thought

After uploading Intersect 2.0 in his brain and to the puzzled look on his teammates, Chuck beats each of its opponents with amazing martial arts skills . “Guys, I know kung-fu” is the phrase that closes the second season of the TV series “Chuck “. It may not be the best script or the best storyline, and it is definitely not the TV-show with the highest scientific accuracy. But there is an interesting question implicit in it: What is the power of our mind? It is not the “Lucy” question, whether we use only 10% of our brain potential, which is interesting. This is a myth that has been widely denied. The interesting question is: is it possible that an individual with low physical training can master martial arts just by uploading theoretical information in his brain?

I am afraid that the answer to the question is no. It is unlikely that skills such as agility or flexibility can be modulated without training. That would be a treat! However It is possible for the brain to play a significant role in how we modulate our physical capabilities. After all, we have all had experiences where our state of mind has had a direct effect on our physical performance.

The Placebo Effect, Myth or Reality?

What is the influence of the cognitive processes in our brain over our physical state? This desire of self-control is what makes both society and science very interested in a phenomenon like the placebo effect. Administering inert substances as if they where the real medication is a common practice as control in medical trials. It is believed that they can also have a healing effect. This seems particularly true in the case of pain, for which placebos seem to have a significant analgesic effect (1). What is even more surprising is that this analgesia is caused by a response of the endogenous opioid system (2). For a broader audience: there is a biochemical response in the brain that produces the pain relief. In pathologies such as depression (3), irritable bowel syndrome (4), or Parkinson’s disease (5), it has been observed that administration of placebos induces an increase in the patients’ quality of life. Furthermore, in the last years, using neuroimaging techniques (positron emission tomography – PET– or functional magnetic resonance imaging – fMRI), it has been possible to identify the areas of the brain that activate in the placebo action process (6).



Nevertheless, it is interesting to note that the placebos mostly affect neurological processes and pathologies where the evaluation of the symptoms is subjective (for the patient or for an observer). It cannot be denied that there are many sources of bias in this type of studies (7), such as the need of the patient please the doctor/evaluator with their responses. It is thus hard to evaluate the validity of these studies with absolute rigor. Actually, recent reviews on the placebo effect bibliography strongly suggest that it has been widely overrated (8,9). A recent study with asthma patients evaluating objective outcomes (forced expiratory volume in 1s – FEV1) shows that placebo administration has no bigger effect than not taking medication at all (10,11). This very same study shows that the patient’s perception is, precisely, of improvement, when in reality, there is none.

Psychoneuroimmunology: Keys to the Relationship Between Body and Mind

On the other hand, the birth of psychoneuroimmunology (PNI) some 30 years ago redefines the relationship between mind and body. Scientist at Rochester University were able to induce a conditioned immunologic response in rats: by administering rats with a saccharine solution combined with an immunosuppressive drug, many of these rats died when taking the solution only containing saccharine (12). This lead to think that it was the immune response that was affected. It is now abundantly clear that the nervous and immune systems are intimately interrelated (13). The nervous system is modulated by a neuropeptide network that also acts in the immune system, making them interdependent (14). This has created a big interest in the stress topic and how it can make us particularly susceptible to some illness (15,16).

However, PNI is often accused of little rigor. It should bepointed out that stress and mood are subjective, hard to evaluate uniformly values. Moreover, the detailed interrelation mechanisms between the nervous and the immune system have not been described (17). TTherefore, until science is further developed in this field, it is sensible to look at those who promise better health by behaving a certain way sceptically. The most objective data we have seem to show that we cannot think ourselves healthier and there is no proof that being happier will prevent us from getting sick. But there is one truth: it is better to be happy.

Lidia Prieto Frías

PhD in Theoretical and Computational Chemistry by Universidad Complutense of Madrid / Freelance



  1. “Placebo-Induced Changes in Spinal Cord Pain Processing”, D. Matre, K.L. Casey, and S. Knardahl. Neuroscience (2006) 26: 559.
  2. “Somatotopic activation of opioid systems by target-directed expectations of analgesia”, F. Benedetti, C. Arduino, and M. Amanzio. Neuroscience (1999) 19: 3639.
  3. “Changes in brain function of depressed subjects during treatment with placebo”, A.F. Leuchter, I.A. Cook, E.A. Witte, M. Morgan, M. Abrams. J. Psychiatry (2002) 159: 122.
  4. “Serum correlates of the placebo effect in Irritable Bowel Syndrome”, E. Kokkotou, L.A. Conboy, D.C. Ziogas, M.T. Quilty, J.M. Kelley, R.B. Davis, A.J. Lembo, and T.J. Kaptchuck. Neurogastroenterol Motil. (2010) 22: 285.
  5. “Effects of perceived treatment on quality of life and medical outcomes in a double-blind placebo surgery trial”, C. McRae, E. Cherin, T.G. Yamazaki, G. Diem, A.H. Vo, D. Russell, H. Elgring, S. Fahn, P. Greene, S. Dillon, H. Winfield, K.B. Bjugstad, and C.R. Freed. Gen. Psychiatry (2004) 61: 412.
  6. “Understanding the placebo effect: Contributions from neuroimaging”, S.C. Lindstone and A.J. Stoessl. Imaging Biol. (2007) 9:176.
  7. “Placebo effect studies are susceptible to response bias and to other types of biases”, A. Hróbjartsson, T.J. Kaptchuck, and F.G. Miller. Clinical Epidemiol. (2011) 64: 1223.
  8. “Is the placebo powerless?”, A. Hróbjartsson and P.C. Gøtzsche. N. Engl. J. Med. (2001) 344: 1594.
  9. “Placebo interventions for all clinical conditions”, A. Hróbjartsson and P.C. Gøtzsche. Cochrane Database Syst. Rev. (2010).
  10. “Active albuterol or placebo, sham acupuncture, or no intervention in asthma”, M.E. Wechsel, J.M. Kelley, I.O.E. Boyd, S. Dutile, G. Marigowda, I. Kirsch, E. Israel, and T.J. Kaptchuck. Engl. J. Med. (2011) 365; 2.
  11. “The placebo effect in asthma”, S. Dutile, T.J. Kaptchuck, and M.E. Wechsler. Allergy Asthma Rep. (2014) 14: 456.
  12. “Behabiorally conditioned immunosuppression”, R. Ader and N. Cohen. Med. (1975) 37: 333.
  13. “Getting nervous about immunity”, K.W. Kelley and R.H. McCusker. Immunol. (2014) 26: 289.
  14. “Neuropeptides and their receptors: A psychosomatic network”, C.B. Pert, M.R. Ruff, R.J. Weber, and M. Herkenham. Immunol. (1985) 135: 820.
  15. “Psychological stress and susceptibility to the common cold”, S. Cohen, D.A.J. Tyrrell, and A.P. Smith. Engl. J. Med. (1991) 325: 606.
  16. “Stress and infectious disease in humans”, S. Cohen and G.M. Williamson. Bull. (1991) 109: 5.
  17. “Immunology: The pursuit of happiness”, J. Marchant,. Nature (2013) 503: 458.

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