Utilization of psychiatric care and antidepressants among people with different severity of depression: a population-based cohort study in Stockholm, Sweden.

PURPOSE: To identify how severity of depression predicts future utilization of psychiatric care and antidepressants.

METHODS: Data derived from a longitudinal population-based study in Stockholm, Sweden, include 10443 participants aged 20-64 years. Depression was assessed by Major Depression Inventory and divided into subsyndromal, mild, moderate and severe depression. Outcomes were the first time of hospitalization, specialized outpatient care and prescribed drugs obtained from national register records. The association between severity of depression and outcomes was tested by Cox regression analysis, after adjusting for gender, psychiatric treatment history and socio-environmental factors.

RESULTS: The cumulative incidences of hospitalizations, outpatient care and antidepressants were 4.0, 11.2, and 21.9% respectively. Compared to the non-depressed group, people with different severity of depression (subsyndromal, mild, moderate and severe depression) all had significantly higher risk of all three psychiatric services (all log-rank test P < 0.001). Use of psychiatric care and antidepressants increased by rising severity of depression. Although the associations between severity of depression and psychiatric services were significant, the dose relationship was not present in people with previous psychiatric history or after adjusting for gender and other factors.

CONCLUSIONS: People with subsyndromal to severe depression all have increased future psychiatric service utilization compared to non-depressed people.