Background: Initial medication non-adherence (IMNA) to antidepressants, which are commonly used to treat depression in primary care (PC), is around 6-12%. Although it is well known that post-initial non-adherence to antidepressants increases the cost of depression, the impact of IMNA on cost is unknown. The aim of this study is to assess the impact of IMNA to Selective Serotonin Reuptake Inhibitors (SSRI) on medical visits and sick leave in patients with depression treated in PC in Catalonia (Spain).
Methods: This was a four-year retrospective register-based study (2011-2014). All PC patients of working age who received a new SSRI prescription and had a diagnosis of depression were included (N = 79,642). Treatment initiation, number of visits and days on sick leave were gathered from the database. We assessed the impact of IMNA on costs with ordered logistic regressions.
Results: The 3-year incidence of IMNA was 15%. Initially non-adherent patients made a lesser number of GP visits (OR = 0.82; 95% CI = 0.79-0.84) but had more days on sick leave (OR = 1.25; 95% CI = 1.20-1.31). There were no differences in the number of specialist visits (OR = 1.04; 95% CI = 0.99-1.08).
Limitations: Differences between adherent and non-adherent patients could be explained by non-observed variables. GP recognition and documentation of depression might be inaccurate. Costs of unpaid work and use of hospital services were not considered.
Conclusions: Although IMNA decreases the use of medical PC services, it increases the number of days on sick leave. This could also indicate worse health status. These consequences are currently overlooked when considering post-initial medication non-adherence.
Keywords: Depression; Healthcare services; Medication adherence; SSRI; Sick leave.
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