Reasons for non-adherence with antidepressants using the Medication Adherence Reasons Scale in five European countries and United States

Depression affects approximately 280 million people worldwide. 50 % of individuals with depression discontinue antidepressant therapy within six months of initiation. The study objective was to determine the extent and reasons for non-adherence with antidepressants in the United States (US) and five European Countries (EU). Data from the National Health and Wellness Study (NHWS), a self-administered, internet-based cross-sectional survey of US adults in 2019 and 5 EU countries in 2020 was included. NHWS participants who self-reported taking daily prescription medication(s) to treat depression responded to the 19 reasons for non-adherence and one global item in the Medication Adherence Reasons Scale (MAR-Scale). Frequencies were used to identify the reasons for non-adherence. Based on data from 7506 US patients and 4230 EU patients, 46.19 % of patients reported non-adherence to at least one reason in the EU, and 42.9 % in the US. The most common reason for non-adherence in the EU was concern about long-term effects and possible side effects from the medication; and in the US, it was simple forgetfulness. Non-adherence lasted longer due to lack of beliefs in needing medication anymore in both US and EU. The self-reported MAR-Scale can have recall bias and an underestimation of non-adherence. The cross-sectional study design captures the adherence behavior only at one point of time. Individuals on antidepressants have to be educated about the need for the medication and their concerns about long term effects and possible side effects from the medication have to be addressed.