Discriminant validity of the Inventory to Diagnose Depression between patients with major depression and pure anxiety disorders

We examined the discriminant validity of the Inventory to Diagnose Depression (IDD), a self-report instrument designed to diagnose major depressive disorder as defined in DSM-III-R. Forty patients with major depression (MD), 20 patients with anxiety disorders, who had not had a lifetime history of depression (ADs), and 40 control subjects completed the IDD. The IDD results were compared in the three contrasting groups (MD vs. AD+control subjects, MD vs. AD, and MD vs. control subjects). The concordance between the IDD and clinical diagnoses, using a structured interview, was significantly high in the three groups (k = 0.81, 0.66, 0.90, respectively). The IDD total score in the MD group was the highest among the three groups and was distinguished from the AD group or control group (P < 0.001, F = 139.9, d.f. = 2,97). However, the IDD occasionally diagnosed subjects with AD as having MD.