Is the Australian National Survey of Mental Health and Wellbeing a reliable guide for health planners? A methodological note on the prevalence of depression

The prevalence of mood and anxiety disorders in Australian women

OBJECTIVE

We aimed to report the prevalence, age-of-onset and comorbidity of mood and anxiety disorders in an age-stratified representative sample of Australian women aged 20 years and over.

METHOD

Mood and anxiety disorders were diagnosed utilising a clinical interview (SCID-I/NP). The lifetime and current prevalence of these disorders was determined from the study population (n = 1095) and standardized to 2006 census data for Australia.

RESULTS

Approximately one in three women (34.8%) reported a lifetime history of any mood and/or anxiety disorder, with mood disorders (30.0%) being more prevalent than anxiety disorders (13.5%). Of these, major depression (23.4%), panic disorder (5.5%) and specific phobia (3.5%) were the most common. The lifetime prevalence of other disorders was low (< or =3%). A total of 14.4% of women were identified as having a current mood and/or anxiety disorder, with similar rates of mood (8.9%) and anxiety disorders (8.0%) observed. The median age-of-onset for mood disorders was 27.0 years and 18.5 years for anxiety disorders.

CONCLUSIONS

This study reports the lifetime and current prevalence of mood and anxiety disorders in the Australian female population. The findings emphasize the extent of the burden of these disorders in the community.

Impact of substance-induced and general medical condition exclusion criteria on the prevalence of common mental disorders as defined by the CIDI

OBJECTIVES

It has been previously argued that the methodology used by the Composite International Diagnostic Interview version 2.1 to assess the substance-induced and general medical condition exclusion criteria are inadequate. As a result prevalence estimates generated from epidemiological studies using this interview may be underestimated. The purpose of the current study was to examine the substance-induced and general medical condition exclusion criteria in the Australian National Survey for Mental Health and Well-being and determine the impact that they have on prevalence estimates of the common mental disorders.

METHOD

Data from the 1997 Australian National Survey of Mental Health and Well-being were analysed. Frequencies were generated as an indication of how many respondents believed that their psychiatric symptoms were always due to a substance or general medical condition. New DSM-IV prevalence estimates were calculated ignoring the application of the substance-induced and general medical condition exclusion criteria and compared to standard DSM-IV prevalence estimates.

RESULTS

The effect of the substance-induced and general medical condition exclusion criteria on final prevalence rates were minimal, with approximately a 0.1% increase when the exclusions were ignored. This equates to a relative difference ranging from no difference for generalized anxiety disorder to an increase of 12% of the base prevalence estimate for agoraphobia.

CONCLUSIONS

In surveys that use the Composite International Diagnostic Interview version 2.1 the substance-induced and general medical condition exclusion criteria have a minor impact on determining final case definition in the majority of mental disorders.

Depression prevalence: is it really increasing?

OBJECTIVE

There is conflicting evidence as to whether depression prevalence is increasing or is stable. Although birth cohort analysis studies show increasing prevalence, longitudinal studies do not. To date there are no published Australian studies providing long-term estimates of depression prevalence. The aim of the present study was to examine the increasing depression prevalence hypothesis in an Australian context.

METHOD

Data from the 1998 and 2004 South Australian Health Omnibus Surveys were re-analysed. In each survey there were >3000 participants who were interviewed. The data were weighted to achieve representativeness prior to analysis. Depression status was classified by the Primary Care Evaluation of Mental Disorders scale (the PRIME-MD) into major, other and no depressions. Both univariate and multivariable analyses were used to examine depression trends over time and to adjust the data for significant background variables.

RESULTS

There was no significant increase in the cases of patients classified with major depression between 1998 and 2004; there was, however, a significant decrease in other depression. The overall unadjusted prevalence of major depression was 7.4% (6.8% in 1998 and 8.0% in 2004) and for other depression it was 9.5% (10.6% in 1998 and 8.4% in 2004). The highest levels of depression, both major and other, were observed among females aged 15-29 years, and the lowest levels among those aged > or =50 years. The strongest predictor of depression was poor overall health status.

CONCLUSION

It is time for the conventional wisdom that depression is increasing to be reconsidered, and for a more realistic perspective, developed from evidence-based analyses, to be accepted.

Bipolar disorders in Australia. A population-based study of excess costs

OBJECTIVE

To estimate the excess costs associated with bipolar disorders in Australia, based on prevalence (using the Mood Disorder Questionnaire (MDQ)) and associated excess burden-of-illness costs.

METHODS

Using data from the 2004 South Australian Health Omnibus Survey (HOS), a weighted cross-sectional survey of 3,015 adults, excess costs were estimated from health service utilisation.

RESULTS

There was a 2.5% lifetime prevalence of bipolar disorders, delineated by the MDQ. Those persons (MDQ positive) reported a significantly greater use of services and a poorer health status and quality of life than those who were MDQ negative. Using the service provision perspective, excess costs of bipolar disorders in Australia were approx $3.97-$4.95 billion.

CONCLUSIONS

These results from an Australian population demonstrate the significant economic burden of bipolar disorders. Our findings emphasise the need for further evaluation of the cost-effectiveness of different treatments, or alternative means of reducing the burden borne by individuals, the health system and the general community.

Reducing the societal burden of depression: a review of economic costs, quality of care and effects of treatment

Depression is a highly prevalent condition that results in substantial functional impairment. Advocates have attempted in recent years to make the 'business case' for investing in quality improvement efforts in depression care, particularly in primary care settings. The business case suggests that the costs of depression treatment may be offset by gains in worker productivity and/or reductions in other healthcare spending. In this paper, we review the evidence in support of this argument for improving the quality of depression treatment. We examined the impact of depression on two of the primary drivers of the societal burden of depression: healthcare utilisation and worker productivity. Depression leads to higher healthcare utilisation and spending, most of which is not the result of depression treatment costs. Depression is also a leading cause of absenteeism and reduced productivity at work. It is clear that the economic burden of depression is substantial; however, critical gaps in the literature remain and need to be addressed. For instance, we do not know the economic burden of untreated and/or inappropriately treated versus appropriately treated depression. There remain considerable problems with access to and quality of depression treatment. Progress has been made in terms of access to care, but quality of care is seldom consistent with national treatment guidelines. A wide range of effective treatments and care programmes for depression are available, yet rigorously tested clinical models to improve depression care have not been widely adopted by healthcare systems. Barriers to improving depression care exist at the patient, healthcare provider, practice, plan and purchaser levels, and may be both economic and non-economic. Studies evaluating interventions to improve the quality of depression treatment have found that the cost per QALY associated with improved depression care ranges from a low of 2519 US dollars to a high of 49,500 US dollars. We conclude from our review of the literature that effective treatment of depression is cost effective, but that evidence of a medical or productivity cost offset for depression treatment remains equivocal, and this points to the need for further research in this area.

Bipolar I and II disorders in a random and representative Australian population

OBJECTIVE

To assess the prevalence of bipolar I and II disorders in an Australian population.

METHOD

The Mood Disorder Questionnaire (MDQ) was administered to 3015 respondents in a random and representative sample in South Australia. Health status, quality of life and demographic data were also collected.

RESULTS

There was a 2.5% lifetime prevalence of bipolar I and II disorders delineated by the MDQ. Those people had a significantly greater use of services and a poorer health status and quality of life than those who were MDQ-negative.

CONCLUSIONS

These results in an Australian population are consistent with other international studies showing a greater prevalence of bipolar disorders than hitherto appreciated.