Antidepressant prescribing in five european countries: Application of common methods to assess the variation in prevalence

Background: Drug utilization studies have applied different methods on various data types to describe medication use which may hamper comparisons across populations. Objectives: The aim of this study was to describe the variation in the prevalence of antidepressant prescribing, applying standard methods, in seven European electronic healthcare databases from five countries. Methods: Patients prescribed with antidepressants were identified from databases from the United Kingdom (UK) (THIN and CPRD), Spain (BIFAP), Denmark (National prescription registry), Germany (Bavarian claims), and the Netherlands (Mondriaan-NPCRD/ AHC) for 2001-2009. Annual prevalence per 10,000 person-years (PYs) was calculated. Prevalence data were standardized according to age/sex distribution of the 2008 European reference population. Stratification was done according to age, sex, antidepressant type (selective serotonin re-uptake inhibitor [SSRI] or tricyclic antidepressants [TCA]) and indications (only year 2008). Results: The age- and sex-standardized prevalence was lowest in the two Dutch (391 and 429 users per 10,000 PYs) and highest in the two UK (913 and 936 users per 10,000 PYs) databases in 2008. Antidepressants were prescribed most often in 20-60 year-olds in the two UK databases compared to the other databases. Prescription of antidepressants was also very high in patients 70 years and older in Denmark with differences being profounder among females than males. SSRIs were prescribed more often than TCAs in all databases except in the German database. The proportion of patients with depression as the recorded indication varied between 12% and 57% in 2008. Conclusions: Despite applying standard methods, variations in the prevalence of antidepressant prescribing were observed between the countries. These variations may be explained in terms of clinical factors as well as database characteristics such as level and frequency of the recorded information.