Influences on antidepressant prescribing trends in the UK: 1995-2011

Purpose: The number of antidepressants prescribed in the UK has been increasing over the last 25 years, however the reasons for this are not clear. This study examined trends in antidepressant prescribing in the UK between 1995 and 2011 according to age, sex and drug class, and investigated reasons for the increase in prescribing over this period.
Methods: Retrospective analysis of antidepressant prescribing data from the Clinical Practice Research Datalink; a large, anonymised, primary care database in the UK. The dataset used in this study included 138 practices, at which a total of 1,524,201 eligible patients were registered across the 17 year period. The proportion of patients who received at least one antidepressant prescription and the number of patients who started a course of antidepressants were calculated for each year of the study. We used person years (PY) at risk as the denominator. The duration of treatment for those starting antidepressants was also examined.
Results: 23% of patients were prescribed an antidepressant on at least one occasion over the 17-year study period. Antidepressant prescriptions rose from 61.9 per 1,000 PY in 1995 to 129.9 per 1,000 PY in 2011. This was largely driven by an increase in prescribing of selective serotonin reuptake inhibitors and 'other' antidepressants. In contrast, incidence rates of those starting antidepressants remained relatively stable (1995: 21.3 per 1000 PY; 2011: 17.9 per 1000 PY). The duration of treatment increased with later starting years, with an increasing proportion of long term use, and decrease in short term use.
Conclusion: The increase in antidepressant prescribing over the study period appears to be driven by an increase in long-term use of these medications.