OBJECTIVES: Depression affects approximately 280 million people worldwide. Literature reports that the overall non-adherence to antidepressants immediately after the start of treatment was 13 to 55.7% and by six months was 52%. However, what is missing in the literature is the extent of non-adherence among individuals based on their level of depression. PHQ-9 score has been used to determine the level of depression as none to minimal, mild, moderate, moderately severe, and severe.

METHODS: Data was used from the 5EU 2022 National Health and Wellness Study (NHWS), a self-administered, annual, internet-based cross-sectional survey of adults in France, Germany, UK, Italy and Spain. Non-adherence was measured using the Medication Adherence Reasons Scale (MAR-Scale) which includes 19 reasons for non-adherence and one global item. NHWS participants who self-reported taking daily prescription medication(s) to treat depression responded to the MAR-Scale. Frequencies were used to identify the reasons for non-adherence.

RESULTS: Of the 4008 respondents (64.22% female; 48.42 mean age), 42.64% were non-adherent. Based on their level of depression, patients with moderate-severe depression were significantly more non-adherent than those with minimal or mild depression. Based on the 19 reasons, 72.27% of the none to minimal depression were adherent, but it decreased to 50.95% for those with severe depression. For all levels of depression, the major reasons were concerns about long term effects and potential side effects from the medicine, forgetfulness, and skipping the medicine to see if it is still needed. Those non-adherent with moderately severe depression missed the medicine an average of 3.04 days/week.

CONCLUSIONS: With ~50% of the patients with moderate-severe depression not taking medicines as prescribed due to concerns about the medicine, providers, payers, and pharmaceutical companies should develop educational interventions to improve adherence.