This is a negative expectation effect.

We all know the placebo effect. This is a positive effect of a drug or treatment that is not attributable to the active ingredients of the drug in question or to the efficacy or intrinsic value of the treatment.

The nocebo effect is the counterpart of the placebo effect. It is a negative expectation effect.

For example, someone says that a certain treatment or medication did not work and that there were many side effects. There is now a good chance that another patient who heard this will also have these side effects with the same medication or treatment.

Apparently, some conditions are more nocebo-sensitive than others. Allergies and asthma are examples of this. For example, someone who is allergic to flowers may react allergically when looking at plastic flowers.

Knowing that there may be side effects when taking a medicine increases the risk of side effects.

Knowing that manipulation can cause damage often leads to complaints afterwards.

So be careful not to use powerful techniques in anxious patients. Anxiety can exacerbate symptoms.

Studies suggest 3 potential mechanisms:

• Creating an expectation.

• Conditioning (e.g. negative experience with other medications).

• Anticipatory unrest.

In neuropathic pain, the nocebo effect probably plays a major role.

• Dodd S. (2017) Current insights in the placebo and nocebo phenomena. Clin. Ther. 2017; 39:456–457.

• Dodd S., Dean O.M., Vian J. & Berk M. (2017) A review of the theoretical and biological understanding of the nocebo and placebo phenomena. Clin Ther. 2017; 39: 469–476.

• Chamsi-Pasha M., Albar M.A. & Chamsi-Pasha H. (2017) Minimizing nocebo effect: Pragmatic approach. Avicenna J. Med. 2017 Oct-Dec; 7(4): 139–143. doi: 10.4103/ajm.AJM5917