A longitudinal population-based study of treated and untreated major depression.

BACKGROUND: Few studies have investigated the factors associated with different outcomes in individuals with major depressive episode (MDE) in relation to mental health service utilization.
OBJECTIVES: This study was to, in depressed individuals who used and did not use mental health services, 1) compare the demographic, psychosocial, and clinical characteristics; 2) estimate the risk of MDE in a 6-year follow-up period; and 3) identify the factors associated with the persistence/recurrence of MDE.
DESIGN: This was a population- based longitudinal analysis.
SUBJECTS: Participants included the longitudinal cohort of the Canadian National Population Health Survey who reported MDE at the baseline survey (n = 609). MEASURES: MDE was measured by the Composite International Diagnostic Interview-Short Form for Major Depression.
RESULTS: In the 6-year follow-up period, 49.8% of participants with treated depression developed subsequent MDE; 28.7% of those with untreated depression reported MDE. Multivariate analyses showed that, among those who reported the use of mental health services, childhood and adulthood traumatic events and functional impairment were related to the recurrence of MDE. Among those who did not use mental health services, reported negative life events and the severity of depressive symptoms were predictive of recurrent MDE.
CONCLUSIONS: The risk of the recurrence of MDE and associated factors differ in mental health service users and nonusers. Future studies need to confirm these results and to identify service barriers for those who do not use the services and who are at a high risk of MDE.