Reliability of the Japanese version of the Inventory to Diagnose Depression

The reliability of the Japanese version of the Inventory to Diagnose Depression (IDD) which is a self-report to diagnose major depressive disorders (MDD) of DSM-III-R, was investigated in 30 cases with MDD and 30 control subjects. On test-retest reliability, the agreement of diagnostic performance was substantial (kappa = 0.64, P < 0.001) for 60 subjects, and scores of total and individual items correlated significantly (P < 0.001) between test and retest except for decreased energy, decreased interest, and decreased concentration. The average score of the total IDD severity at test (38.4) was significantly higher than that at retest (28.0; P < 0.01). However, excluding the recovered 10 cases, there was no significant difference seen on the average total score between test and retest (38.8, 30.1, respectively). Internal consistency (Cronbach's alpha = 0.80) and split-half reliability (0.79) were sufficient, and item-total correlations of the IDD were significant (P < 0.01) except for weight gain. The IDD might be useful as a screening tool and for clinical evaluation of subjects in Japan; however, it is necessary to examine the validity of this instrument.