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Can the reasons for non-adherence be identified?

“if health care professionals are asked to rate adherence levels of their own patients compared with those with the same condition but not treated by them – then they will consistently rate their own patients as more adherent.” (Clyne et al., 2016)

The COM-B model hypothesizes that interaction between three components, Capability, Opportunity and Motivation (COM) causes the performance of Behavior (B) and hence can provide explanations for why a recommended behavior is not engaged in.

“We still haven’t got it right in the health services that people will be treated as a whole person and not as a bundle of conditions each treated in a separate area.”

“Some people just don’t want to take medications but did not express this to the prescriber at the initial appointment. I always ask my patients how they are taking the medications, what time of day, how often, how many, if they are having any side effects?”

Some reasons for non-adherence:

  1. the condition presents few symptoms
  2. lack of insight and side effects
  3. forgetting
  4. not needing medication (“I’m fine”)
  5. not wanting to take drugs.
  6. lack of information about the drug, how it works, how it should be taken why it is required, lack of information about condition being treated.

“GPs are under a lot of pressure with the numbers of patients coming through their doors which is one of the reasons why they often limit the consultation time. The NHS realises this pressure and now a large number of pharmacists are being employed in GP surgeries to help relieve the pressure from the GP so that they can spend more time with their patients. There is a big push at the moment to encourage patients to visit their local pharmacy first who can often help with a variety of different issues. There is still a lot of work to be done however. Pharmacists have the knowledge to explain how the medication works, and the importance of taking it.”


The COM-B framework

The COM-B framework proposes that people need the capability, the opportunity, and motivation to perform a particular behaviour. It takes into account the wide range of factors that influence behaviour and was developed with reference to existing theories of behaviour, not just models focused on people’s beliefs. Let’s look at each of these components in turn. Capability is the psychological and/or physical ability to engage in that behaviour. So when applied to medicines’ adherence, psychological capability can include the patient’s capacity to understand, to remember, to plan their treatment. So, for example, a deficit in perspective memory function means that a patient’s ability to remember to do something in the future, i.e. To take their medicines, can be impaired.

Physical ability refers to the level of physical skill required to actually use the medicines or devices, such as asthma inhaler or an insulin pen needle. Another example of this would be the inability to swallow tablets, either due to dry mouth, which can be a side effect of some medicine or treatment, or simply because of the gag reflex, which could prevent someone from doing so regardless of the size of the tablet. Opportunity covers both the physical and social factors that are external to the individual and that make their behaviour possible or prompted.

These factors could include the quality of health care communication and also the physical characteristics of the prescribed treatment, such as the regimen complexity and also the taste and smell of the medicine itself. Opportunity factors also include family and friends, i.e. significant others, who can encourage medicine taking and equally discouraging. Social factors refer to the wider social context, which may include religious beliefs and cultural beliefs. For example, a greater acceptance of traditional alternative therapies in comparison to pharmacologic treatments may lead to non-adherence to prescribe medicines. Motivation includes the want or need to perform the behaviour more than any other competing behaviours at that moment. And this is driven by both reflective and automatic brain processes.

Reflective, or deliberate, processes referred to the patient’s beliefs about the treatment and the illness. For example, a patient’s beliefs about the negative impact of side effects both anticipated and experienced or the perceived seriousness of their condition, as we identified earlier in the self-regulatory model. Automatic processes include innate dispositions and impulses arising from past learning. For example, patients may establish a routine whereby their medicine-taking becomes associated with a daily behaviour, such as brushing their teeth or setting their alarm clock. When this routine is disrupted, the queue to action may be missed so that medicines are not taken.

For example, if the patient associates setting their alarm clock in the evening with taking their tablets, this routine may be disrupted if a patient is on holiday. In addition, the COM-B is a dynamic model in which the three components interact with each other. The complex treatment regimen might be beyond the planning capability of a patient. So it may negatively influence the decision of whether or not to continue taking the treatment over time, especially if a person is worried about a health condition, which they think might have a negative effect on their ability to do their job. So in this example, there’s an interaction between psychological capability, reflective motivation, and the social opportunity factors.


Behavior Change Techniques

The following behavior change techniques are considered to be useful to support medicines adherence:

A good tool that helps to explain patients the reasons to consider taking medicines are the decision aids tools that shows with pictures how their risk can be decreased by taking a medicine, at the same time they can also explore if this lowered risk is sufficient for them to take sometimes a life long therapy. An example of decision aid is available here.

“Adherence issues can change over time for individual patients. New challenges may arise especially when there is a change in the delivery of care.”

“There are many factors which contributes to whether a patient adheres to their medication or not. These can change over time as the patients disease state changes or personal circumstances change. It is important as a clinician to recognize when these changes happen in our patients to ensure we recognize non adherence as soon as it starts happening.”

“There are even more challenges to effective medicine taking if people are not able to live stable lives, for a number of reasons.”

“Having a holistic understanding of the patient’s individual experience will allow us to better support them – not just with their medicines but with their health overall.”



Clyne W, McLachlan S, Mshelia C et al (2016) “My patients are better than yours” : optimistic bias about patients’ medication adherence by European health care professionals. Patient Preference and Adherence, 10, 1937-1944.

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