An item response analysis of the DSM-IV criteria for major depression: findings from the Australian National Survey of Mental Health and Wellbeing.

BACKGROUND

This study examines the psychometric properties and presence of gender bias in the major depression criteria using data from the Australian general population.

METHODS

Data came from a subsample of respondents from the 1997 National Survey of Mental Health and Wellbeing (NSMHWB; n=2061). A two-parameter logistic model was employed to yield severity and discrimination parameters, and the IRT log-likelihood-ratio test for differential item functioning (IRTLRDIF) procedure was utilized to evaluate gender bias.

RESULTS

DIF analyses indicated that the psychomotor difficulties criterion was endorsed at lower levels of severity by males than females. In general, the criteria were arrayed along a continuum of depression severity. Discrimination was greatest for concentration difficulties/indecision and lowest for death/suicidal thoughts and worthlessness/guilt. Worthlessness/guilt, psychomotor difficulties, and death/suicidal thoughts tapped the severe end of the depression continuum, whereas concentration difficulties/indecision and sleep disturbance tapped the mild range.

LIMITATIONS

The inclusion of stem questions precluded examination of two core symptoms of depression (depressed mood and loss of interest).

CONCLUSIONS

Collectively, the criteria performed well in defining a latent continuum of major depression. Few gender differences were observed, with the exception of the psychomotor difficulties criterion. Quantitative and qualitative analyses collectively hold promise of providing a scientifically rigorous basis for empirically-based modifications to the psychiatric classification system.