Changes in the prevalence of major depression in an Australian community sample between 1998 and 2008

To identify changes in the prevalence of major depression between 1998, 2004 and 2008 in South Australia.

Face-to-face Health Omnibus surveys were conducted in 1998, 2004 and 2008 with approximately 3000 participants aged 15 years and over, who were random and representative samples of the South Australian population. Each survey used the same methodology. Outcome measures were: major depression as detected by the Mood module of the Primary Care Evaluation of Mental Disorders instrument; mental health literacy by recognition and exposure to classical symptoms of depression; and health status using the SF-36 Physical and Mental Component summaries.

There was a significant increase in the prevalence of major depression from 6.8% (95%CI: 5.9%-7.7%) to 10.3% (95%CI: 9.2%-11.4%; χ² 24.59, p < 0.001) between 1998 and 2008. Significant increases were observed in males aged 15-29 and females aged 30-49 years. There was no significant increase in any other sub-group. The strongest predictor of major depression was health status. Participants with poor/fair mental health literacy were 37% less likely to be classified with major depression.

The prevalence of major depression increased significantly in South Australia over the last decade and there was a reduction in mental health status and an increase in persons reporting poor health. Unexpectedly, having poor or fair mental health literacy was significantly protective for major depression. Ideally, public health initiatives should result in an improvement in health, but this did not appear to have occurred here.