Factors influencing variation in prescribing of antidepressants by general practices in Scotland.

BACKGROUND The prescribing of antidepressants has been rising dramatically in developed countries. AIM As part of an investigation into the reasons for the rise and variation in the prescribing of antidepressants, this study aimed to describe, and account for, the variation in an age-sex standardised rate of antidepressant prescribing between general practices. DESIGN OF STUDY Cross-sectional study involving analyses of routinely available data. SETTING A total of 983 Scottish general practices. METHOD Age-sex standardised prescribing rates were calculated for each practice. Univariate and multivariate regression analyses were undertaken to examine how the variation in prescribing was related to population, GP, and practice characteristics at individual practice level. RESULTS There was a 4.6-fold difference between the first and ninth deciles of antidepressant prescribing, standardised for registered patients' age and sex composition. The multivariate model explained 49.4% of the variation. Significantly higher prescribing than expected was associated with more limiting long-term illness (highly correlated with deprivation and the single most influential factor), urban location, and a greater proportion of female GPs in the practices. Significantly lower prescribing than expected was associated with single-handed practices, a higher than average list size, a greater proportion of GP partners born outside the UK, remote rural areas, a higher proportion of patients from minority ethnic groups, a higher mean GP age, and availability of psychology services. None of the quality-of-care indicators investigated was associated with prescribing levels. CONCLUSION Almost half of the variation in the prescription of antidepressants can be explained using population, GP, and practice characteristics. Initiatives to reduce the prescribing of antidepressants should consider these factors to avoid denying appropriate treatment to patients in some practices.