The expression non adherence (adherence or non-adherence to therapy) refers to all cases in which the patient does not follow doctor’s suggestions about therapy or how to behave concerning it.

In Western countries, adherence to treatment for patients with chronic diseases is only 50%. Poor adherence to treatment primarily occurs in missing intake.

Because of poor adherence, the best treatment can become inefficient or less efficient, as well as exposing the patient to risks, such as side effects caused by therapy interruption and development of resistance.

Consequences of poor adherence are clinical and psicosocial, with a negative impact on patient quality of life, but also economic, because it generates a waste of resources of the national health system.