Trends in primary care antidepressant prescribing 1995-2007: a longitudinal population database analysis

Background: Antidepressant prescribing is increasing worldwide, prompting policy interventions and targets to halt the rise. Aim: To examine time trends in GP antidepressant prescribing using patient-level data. Design and setting: Longitudinal population database of all community pharmacy dispensed prescriptions for all 325 000 residents of the Tayside region of Scotland. Method: In each of 3 study years (1995/1996, 2000/2001 and 2006/2007), the volume of antidepressants prescribed was calculated, and numbers of patients prescribed antidepressants in each year, mean treatment duration, and mean dose per patient in that year examined using descriptive statistics. Results: Total drug volume increased threefold between 1995/1996 and 2006/2007, largely driven by increases in selective serotonin reuptake inhibitor (SSRI) prescribing, and laterally also in 'other' antidepressant prescribing. Tricyclic prescribing is static, but low-dose amitriptyline increasingly dominates this drug class. Increased drug volume was initially driven by increasing patient numbers (from 8.0% of the population prescribed at least once in 1995/1996 to 11.9% in 2000/2001) and increased treatment duration (from 170 days in the measurement year to 200). Latterly, drug volume increases are increasingly attributable to longer duration of treatment and higher mean daily dose. Conclusion: The large rise in antidepressant volumes is caused by a complex mixture of more patients being prescribed SSRI and 'other'antidepressants, the use of higher doses, and longer durations of treatment, with the balance changing over time. Tricyclic prescribing is now largely low dose, and probably for conditions other than depression. Interventions to improve the quality of antidepressant prescribing need to be more subtle than blanket targets to reduce the total volume of antidepressants prescribed.