Exploring potential explanations for the increase in antidepressant prescribing in Scotland using secondary analyses of routine data.

Background

Antidepressant prescribing in general practice has dramatically increased since the beginning of the last decade.

Aim

To determine if the increase in antidepressants prescribed in Scotland between 1995 and 2001 was due to increase in incidence, prevalence, care-seeking behaviour by patients, or identification by GPs of depression.

Method

Secondary analysis of routine data. Prescribing information was obtained from Information and Statistics Division Scotland, psychosocial morbidity from the Scottish Health Surveys of 1995 and 1998 and GP consultations from the continuous morbidity recording (CMR) dataset. Annual trends in antidepressant prescribing for prescriptions, gross ingredient cost and defined daily doses (DDDs) were examined for all Scottish Practices and 54 stable CMR practices (175 955 patients). Prevalence of psychological morbidity in responders with a General Health Questionnaire score A, their contact probability and contact frequency was compared in the 1995 and 1998 Scottish Health Surveys. Changes in diagnostic and GP consultation patterns in CMR practices were compared.

Results

Total prescriptions for antidepressants increased from 1.5 million in 1995-1996 to 2.8.million in 2000-2001. The gross ingredient cost increased from 20 pound to 244 million and total DDDs from 44.5 to 93.2 million. Prescription trends in CMR practices were similar. Overall prevalence of psychological morbidity was the same in the 1995 and 1998 Scottish Health Surveys. Percentage of consultations in CMR practices for new diagnoses of depression decreased from 1.7 to 1.3%, the depression-related contact rate decreased and annual prevalence rates for depressive illness were stable between 1998-1999 and 2000-2001.

Conclusions

There is no evidence of an increase in incidence, prevalence, care-seeking behaviour or identification of depression during the period of a sharp increase in antidepressant prescribing. Further work is required to explain the increase.