Seasonal Variation in Antidepressant Prescribing: Year on Year Analysis for England

The number of prescriptions for antidepressants in England has almost doubled in the past decade. The objective of this study was to examine if this growth and seasonal variation in prescribing rates of different antidepressants by general practice are linked.

The number of prescriptions and quantity of antidepressants prescribed each month between January 1, 2014, and December 31, 2019 from the general practice prescribing data reports for each British National Formulary code and practice were analyzed. The data were aggregated to obtain the monthly total and analyzed to identify patterns by medication.

: We included all oral antidepressant medications prescribed in England in 2019 for a total of 74 million prescriptions, which was equivalent to 2.36 billion defined daily doses. Monthly variation in daily prescribing percentage of the annual average over the year in total and antidepressant medications showed small but generally consistent seasonal variation, an average of up to 1.61% in total items and 1.47% in defined daily dose (highest prescribing in November/December). The seasonality varied by agents, with agents having highest seasonality also showing the most growth (r² = 0.5, P = .002). This relation was strongest for mirtazapine and sertraline. There was a clear relation between average seasonality and year on year growth in antidepressant medication prescribing for 2016-2019 (r² = .536, P = .002).

The study confirmed seasonal variation in antidepressant prescribing with a peak in November/December. Growth in the antidepressant prescribing year on year was related to seasonality and requires further scrutiny in terms of understanding the factors that underlie the seasonal variation seen.