Aim of the study:
To describe the prevalence and factor structure of anxiety-depression in a community sample and to derive indicators for treatment planning.

Subject or material and methods:
A sample of 398 members of the Electoral Roll for the New England region of Australia were recruited at random and completed the Zung Self-rating Anxiety Scale and the Zung Self-rating Depression Scale.

Results:
The prevalence of anxiety-depression was 28.1%, over twice that for either anxiety or depression alone. The anxiety-depression construct was comprised of four underlying factors: Cognitive Agitation & Depressed Mood, Pessimism, Cardiovascular Reactivity, and Pain & Sleep Disturbance. There were different patterns of these four factors across Anxiety-only, Depression-only and combined anxiety-depression, with evidence for a unique symptomatological profile for participants with clinically significant levels of anxiety-depression.

Discussion:
Anxiety-depression comorbidity was relatively common in this community sample of Australians, with over a quarter of participants meeting the cutoff for clinically significant scores on the combined SAS-SDS construct. These results also highlight the need to consider the presence of clinically significant anxiety-depression as representing a larger proportion of this sample than either anxiety or depression alone.

Conclusions:
Treatment decisions for anxiety and depression need to go beyond consideration of the two disorders separately to include the underlying factor severity of the combined construct of anxiety-depression.