Comparison of depressive symptom severity scores in low-income women.

BACKGROUND

The Beck Depression Inventory, Second Edition (BDI-II), and the Patient Health Questionnaire-9 (PHQ-9) are considered reliable and valid for measuring depressive symptom severity and screening for a depressive disorder. Few studies have examined the convergent or divergent validity of these two measures, and none has been conducted among low-income women-although rates of depression in this group are extremely high. Moreover, variation in within-subject scores suggests that these measures may be less comparable in select subgroups.

OBJECTIVE

We sought to compare these two measures in terms of construct validity and to examine whether within-subject differences in depressive symptom severity scores could be accounted for by select characteristics in low-income women.

METHODS

In a sample of 308 low-income women, construct validity was assessed using a multitrait-monomethod matrix approach, between-instrument differences in continuous symptom severity scores were regressed on select characteristics using backward stepwise selection, and differences in depressive symptom classification were assessed using the Mantel-Haenszel test.

RESULTS

Convergent validity was high (rs = .80, p < .001). Among predictors that included age, race, education, number of chronic health conditions, history of depression, perceived stress, anxiety, and/or the number of generalized symptoms, none explained within-subject differences in depressive symptom scores between the BDI-II and the PHQ-9 (p > .05, R2 < .04). Similarly, there was consistency in depressive symptom classification (χ2 = 172 and 172.6, p < .0001).

DISCUSSION

These findings demonstrate that the BDI-II and the PHQ-9 perform similarly among low-income women in terms of depressive symptom severity measurement and classifying levels of depressive symptoms, and do not vary across subgroups on the basis of select demographics.