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Therapy adherence

What is therapy adherence?

Therapy adherence is a term that can be explained in multiple ways. At the moment the emphasis of therapy adherence is on the extent the behaviour of the patient corresponds with the agreement between the patient and the practitioner. It’s assumed that a lessened therapy adherence can lead to a heightened risk of morbidity, mortality and higher health costs. Measures that increase therapy adherence are attempting to decrease these heightened risks and to reduce health costs.

It’s assumed that it’s not only necessary that the patients follow the agreed upon course of the treatment, but that it’s also necessary for the patient to keep this up. Considering the increasing incidence and prevalence of chronic conditions it’s also necessary that the patients not only have sufficient access to treatments, but are also assisted with this. This last part is a challenge for both doctors and pharmacists.

Where in the past the emphasis was on the correctly adhering to the prescribed dosage schedule, the emphasis has now shifted to an agreement between patient and practitioner about the course of the treatment. This agreement is a condition for therapy adherence. Acceptance and willingness of the patient play an important part in this.

To interpret the data about therapy adherence it’s important to distinguish between correctly adhering to an agreement(dosage schedule) between the patient and the practitioner and the continuity (persistence) or the period of time between starting and stopping the treatment. Both aspects determine the effectiveness of a drug. (drs H. A.W van Onzenoort)


What is therapy

Therapy non-adherence can be defined as the extent to which the patient’s behavior does not match that of the agreed recommendation made by the prescriber.

Reasons for therapy non-adherence

A patient can have different reasons for being non-adherent. These reasons can be divided into two groups: unintentional or intentional (King’s College London, n.d.).


Therapy non-adherence, not just a problem on the
patient's side but on the side of the prescriber as well.


A patient is unintentionally non-adherent when (s)he is willing to take in his/her medication (correctly), but (s)he encounters difficulties regarding the ability and/or resources to do so. There are internal as well as external factors that influence this:


  • Patients simply forgot to take their medication, because they did not remember to do so or they forgot whether they already did it or not;
  • Someone who got a chaotic lifestyle might find it hard to put their medication intake moment(s) in their daily routine.


  • Some people might have difficulties in accessing healthcare;
  • It might also be possible that patients cannot afford their prescribed medication;
  • It might also occur that patients encounter practical barriers.

A research done by the Boston Consulting Group and Harris Interactive (2002) among 10.000 chronic patients has shown that the majority (24%) of the non-adherent patients gave forgetting to use or refill their medication as main reason of their non-adherence. Other main reasons they mentioned were the unwanted side-effects (20%) and the medication costs (17%).


Intentional non-adherence is the situation in which the patient has made a considered decision that (s)he will not be taking his/her medication in a way that has been recommended by the prescriber. This lack of motivation to take in their medication correctly can be caused by their beliefs of their illness and/or treatment.

Patients have beliefs of their illness, regarding:

  • Identity: what their illness condition is;
  • Cause: what it caused;
  • Cure & Control: how they (or others) can cure;
  • Consequences: how much a treatment will have an impact on their illness and how much the illness will have an impact on their lives;
  • Timeline: how long the illness will last.

These illness beliefs might also influence the beliefs a patient might have of their treatment. If a patient has a certain belief of what his/her illness condition is, (s)he might think that taking in his/her medication is not necessary. Patients might also consider the negative consequences of taking in their medication, e.g. side effects or the fear of becoming dependent of it.

Not just a patient’s problem

As the definition of the term ‘adherence’ says, it is about an agreement between the patient and the prescriber. Therefore non-adherence is not just a problem at the patient’s side, but also on the prescriber’s side. The quality of communication can play an important role here. When the prescriber understands the patient’s situation and/or shows his/ her empathy with the patient, this might positively influence the patient’s illness and treatment beliefs. This also applies to the clarity of the information about the illness and its treatment(s) the prescriber communicates towards the patient.

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