Mental health in the suburbs: an investigation of differences in the prevalence of depression across Canberra suburbs using data from the PATH Through Life Study

Validation of four measures of mental health against depression and generalized anxiety in a community based sample

There is a need to validate screening measures of affective and generalized anxiety disorders for use in epidemiological surveys of mental health in the general population. This study examined the diagnostic accuracy of the Patient Health Questionnaire (PHQ-9), Goldberg Anxiety and Depression Scales (GAS, GDS) and the 12-item Short Form Health Survey (SF-12) Mental Health Component Summary Scale (MCS-12) in a population based longitudinal study in Australia. We report analyses of two narrow age birth cohorts in the Personality and Total Health (PATH) through life study (ages 32-36 and 52-58). Depressive episodes (severe, moderate, and mild), dysthymia and generalized anxiety disorder were diagnosed according to International Classification of Diseases (ICD-10) criteria using the World Health Organisation (WHO) Composite International Diagnostic Interview (CIDI) as a criterion. All scales had high concordance with their target 30-day diagnoses, with area under the Receiver Operating Characteristic (ROC) curve (AUC) ranging between 0.85 and 0.90. The PHQ-9, GDS, GAS and MCS-12 were all valid instruments for identifying possible cases of depression and anxiety, and assessing the severity of these common mental disorders in the general population. We report recommended cut-points for each scale, though note that the optimal cut-point on mental health screening instruments may vary depending on the context of test administration.

Socioeconomic differences in antidepressant use in the PATH Through Life Study: evidence of health inequalities, prescribing bias, or an effective social safety net?

BACKGROUND

Depression is more common amongst those who are economically disadvantaged. However there is inconsistent evidence concerning the relationship between socioeconomic position and antidepressant use. Moreover, evidence of greater antidepressant use amongst those of lower socioeconomic position may reflect their greater psychiatric morbidity, a prescribing bias towards pharmacological treatments, or provide evidence of an effective social safety net. This study investigates these issues whilst addressing methodological limitations of earlier studies.

METHOD

Data were from a large, random community survey of Australian adults (N=4493) with linked administrative data for primary-care service use. Depression was measured using the Patient Health Questionnaire, with other measures of current mental health and history of depression included in analysis. Multiple personal indicators and a combined measure of social disadvantage were considered. A series of analyses systematically examined competing explanations for socioeconomic differences in depression and antidepressant treatment.

RESULTS

Markers of socioeconomic disadvantage were associated with a greater likelihood of antidepressant use. This finding was not attributable to the higher rates of depression amongst the disadvantaged. A similar pattern of results was evident for non-pharmaceutical treatments (primary care consultations). Socioeconomic position was not associated with use of complementary medications for depression, not covered by Australia's social safety net.

LIMITATIONS

Analysis did not consider specialist mental health services.

CONCLUSIONS

Socially disadvantaged respondents reported greater antidepressant use and service use after controlling for current depression symptoms. This pattern of findings suggests Australia's universal health-care system and social safety net may help address potential inequalities in health care.