Antidepressant drug prescribing in general practice: a 6-year study.

We analysed antidepressant drugs (AD) prescription ratios of the GPs working in Verona, Italy, over a 6-year period (1983-1988). The data, provided by a local drug information system (SIF-USL), were calculated as Defined Daily Dose (DDD), which is the unit of drug consumption recommended by WHO. We found that DDD/1000 patients/day increased over the period, mainly because of an increase in the use of 'second-generation' antidepressants and other non-tricyclic antidepressants. An increase in the levels of prescription of AD was observed over the 6 years. This increase was statistically significant when comparing the first (1983) with the other years. Low correlations were found between DDD/patient/year ratios and GPs' age, sex and list size. Harmonic analysis of the seasonal variations in prescriptions of AD revealed a substantial pattern of seasonality, in which the first four harmonics accounted for the greater part (95.5%) of the seasonality. AD prescribing may be linked more closely to seasonal holiday patterns than to seasonality in the onset of depressive disorders.