Changing patterns of antidepressant use and costs in a health maintenance organisation

This study examined changes in the utilisation and costs of different antidepressants, particularly the selective serotonin reuptake inhibitors (SSRIs), and changes in the use of mental health services in a US health maintenance organisation (HMO) over the 8-year period following the introduction of SSRIs. It was hypothesised that SSRIs would be used increasingly in this setting, and that SSRI users would show a pattern of mental health service utilisation that was indicative of more severe psychiatric illnesses or prior treatment failures. Both hypotheses were accepted. The use of antidepressants nearly tripled over the 8-year period, with SSRIs showing the largest increase; per capita antidepressant costs increased more than 10-fold, largely because of the high cost per unit of SSRIs. Estimated daily doses of SSRIs were largely within the recommended ranges, although the duration of use was short if their primary purpose was the treatment of depression. Incident (first-time) users of SSRIs, and patients who switched to SSRIs from other antidepressants, used more inpatient and outpatient mental health services than users of other antidepressants. Use of the psychiatric hospital among antidepressant users increased, then decreased back to its first year level, psychiatric hospital days appeared to decrease over time, and outpatient mental health visits increased. The inverse relationship between use of SSRIs and use of inpatient mental health services suggests the need for a cost-effectiveness analysis in this setting.