Table 1.

Illustration of changes and adaptations of the original definition of patient compliance over the years

Definition	Authors – Year
Compliance is the extent to which the patient's behaviour (in terms of taking medications, following diets or executing other lifestyle changes) coincides with the clinical prescription.	Sackett & Haynes (1976) [64]
Compliance is the extent to which the patient's behaviour coincides with the clinical prescription, regardless of how the latter was generated.	Sackett & Haynes (1976) [64]
Compliance is the extent to which a person's behaviour (in terms of taking medication: following diets, or executing other lifestyle changes) coincides with medical or health advice.	Haynes et al. (1979) [143]
Compliance is the extent to which an individual chooses behaviours that coincide with a clinical prescription, the regimen must be consensual, that is, achieved through negotiations between the health professional and the patient.	Dracup & Meleis (1982) [144]
Adherence is the degree to which a patient follows the instructions, proscriptions, and prescriptions of his or her doctor.	Meichenbaum & Turk (1987) [145]
Adherence is the extent to which a person's behaviour – taking medication, following a diet, and/or executing lifestyle changes – corresponds with agreed recommendations from a health care provider.	World Health Organization; (2003) [3]
Adherence is the extent to which a patient participates in a treatment regimen after he or she agrees to that regimen.	Balkrishnan (2005) [146]