The influence of symptoms of anxiety and depression on medication nonadherence and its causes: a population based survey of prescription drug users in Sweden

PURPOSE The purpose of this study was to evaluate the associations between self-reported symptoms of anxiety and/or depression, nonadherent (NA) behaviors, and reasons for NA to medication regimens. METHODS A population based cross-sectional study with questionnaire was performed in the general Swedish population. The participants were 2,802 prescription drug users aged 18-84 years. The questionnaire covered use of prescription drugs, symptoms of anxiety and/or depression, based on the Hospital Anxiety and Depression Scale (HADS), various NA behavior types, intentional and unintentional, and various reasons for NA. RESULTS Symptoms of anxiety and depression, independently and in combination, were associated with unintentional and intentional NA, with a stronger association with intentional NA. Regarding the reasons given for NA, for example anxiety, independently or in combination with depression, was associated with a fear of developing adverse drug reactions (ADRs). Depression, independently or in combination with anxiety, on the other hand, was associated with the actual development of ADRs. CONCLUSION A cross-sectional design such as this does not allow assessment of causality derived from the results. However, the results indicate that patients experiencing symptoms of psychological distress are at increased risk of NA, especially intentional NA, and could therefore benefit from extra attention from the health care professional. Patients with symptoms of anxiety and/or depression should be identified and monitored for the development and/or fear of ADRs, in order to improve adherence to medication regimens.