gms | German Medical Science

Introduction: Adherence to medication is crucial to achieve treatment control in chronic disease. The necessity-concerns framework postulates that patients’ adherence behaviour is influenced by beliefs about the necessity of prescribed medicines and the concerns patients might have regarding these medicines. It has been shown among patients suffering from rheumatoid arthritis (RA) that necessity beliefs are positively associated with medication adherence and concerns are negatively associated (Horne, 2013). We investigated the influence of depression on the associations between beliefs about medicines and medication adherence in patients with RA.

Research Question: Does depression moderate the associations between patients’ beliefs about medicines (necessity, concerns) and medication adherence?

Methods: Adult patients with physician-diagnosed RA completed the “Beliefs about Medicines-Questionnaire” (BMQ), the “Medication Adherence Report-Scale” (MARS) and the “Hospital Anxiety and Depression-Scale” (HADS). 361 patients recruited in inpatient and outpatient care (30.5% male, mean age 60.2 years (SD=13.4)) provided informed consent and were included in the study. The BMQ-subscales “necessity” and “concerns” (scores ranging from 1 to 5) were used as main explanatory variables. MARS scores (ranging from 5 to 25) were dichotomized into a binary variable indicating full adherence (25) vs. suboptimal adherence (≤24) which was used as dependent variable. The score on the “depression” scale (ranging from 0 to 21) of the HADS was included as moderator variable. Multivariate logistic regression analyses were computed for both the “necessity” and the “concerns” subscale, each including an interaction term with depression. If the interaction term was significant, simple slope analyses were conducted. A large number of variables were investigated for inclusion as potential confounders by means of univariate analysis with an entry p value of .20. Sex, the number of prescribed RA medicines and self-rated pain were found to be associated with adherence in univariate analyses and were thus included as potential confounders. All analyses were computed using SPSS.21 for Windows.

Results: 31.9% of patients were adherent, and 34.4% showed elevated depression scores (HADS≥8). Patients’ beliefs about the necessity of medicines were positively associated with medication adherence (b=0.53, p=.02). Depression moderated the association between necessity beliefs and medication adherence (b=0.14, p=.03), revealing stronger associations in patients with higher levels of depression. Patients’ concerns were negatively associated with medication adherence, albeit this association was not significant (b=-0.34; p=.06). It was however altered by depression (b=0.07, p=.05) and was less pronounced in patients with high levels of depression compared to those with moderate or low levels.

Discussion: Our study showed that symptoms of depression as captured by the HADS moderate the associations between beliefs about medicines and medication adherence among patients suffering from RA. These findings suggest that depression might alter the ways in which RA patients translate their beliefs into behaviours. Necessity beliefs seem to be stronger and concerns seem to be weaker predictors of adherence in those with symptoms of depression.

Practical implications: Given prevalences of depression in RA of about 30% (Matcham, 2013) it is important to understand how this comorbidity affects medication adherence and which potential modifiable factors (such as patients’ beliefs) could be targeted in interventions.