Medication/drug non-adherence can be defined as either the intentional or unwitting failure to take medications as prescribed. By not following the prescriber’s orders correctly, the patient will experience decreased effectiveness of treatment which can lead to the worsening of their condition.  In the United States, nearly 4 million prescriptions are written annually, according to a Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report. Studies referenced in an Annals of Internal Medicine article indicate that 20-30% of medication prescriptions are never filled and approximately 50% of medications for chronic disease are not taken as prescribed due to many different factors.

A person may decide not to take their medications as prescribed due to a range of factors, including past experiences. Some more common reasons include:

• Cognitive conditions: Conditions such as dementia and Alzheimer’s disease may cause a person to take their medication in a way other than their doctor has prescribed.
• Concerns about competence: This might involve not trusting the doctor to make appropriate decisions, possibly because the doctor is unaware or dismissive of cultural factors or personal preferences or beliefs.

• Concerns about side effects or dependency: A related issue may be feeling overwhelmed by the number of side effects listed on packaging or websites.

• Denial: A person may not accept that they have a health issue that requires this treatment.

• Depression: People experiencing depression are less likely to take medications exactly as prescribed, the American Medical Association report.

Other causes include difficulty managing multiple medications, not understanding the purpose of taking a medication, and poor health literacy.

These causes can be broken down into two categories: unintentional non-adherence, which is when patients want to follow treatment but are prevented from doing so by obstacles out of their control, and intentional non-adherence, which is when patients choose not to follow treatment advice.

Considering the high percentage of patients who do not take their medications as described, do not to go into appointments and discussions with patients assuming adherence is occurring. This could put a patient’s wellbeing at risk if a new prescription is issued or existing therapy changed based on the belief that the patient’s current symptoms reflect the effects of the current regimen when, in fact, the patient is not taking medications as instructed.

The cost of medications is a key reason for drug non-adherence. Many drugs are very expensive, even for people with good health insurance. High costs may lead many people to ration medications or never fill prescriptions. A person may be unable to access treatment that their insurance plan does not cover. Also, some drugs may be unavailable regionally.