Our study aimed to establish the relationship between the number of depressive symptoms and the clinical characteristics of major depressive disorder (MDD). This would enable us to predict the clinical significance of the number of depressive symptoms in MDD patients. Using data from the Clinical Research Center for Depression (CRESCEND) study in Korea, 853 patients with DSM-IV MDD were recruited. The baseline and clinical characteristics of groups with different numbers of depressive symptoms were compared using the χ2 test for discrete variables and covariance (ANCOVA) for continuous variables. In addition, the scores of these groups on the measurement tools were compared by ANCOVA after adjusting the potential effects of confounding variables. After adjusting the effects of monthly income and history of depression, a larger number of depressive symptoms indicated higher overall severity of depression (F [4, 756] = 21.458, P < 0.001) and higher levels of depressive symptoms (F [4, 767] = 19.145, P < 0.001), anxiety symptoms (F [4, 765] = 12.890, P < 0.001) and suicidal ideation (F [4, 653] = 6.970, P < 0.001). It also indicated lower levels of social function (F [4, 760] = 13.343, P < 0.001), and quality of life (F [4, 656] = 11.975, P < 0.001). However, there were no significant differences in alcohol consumption (F [4, 656] = 11.975, P < 0.001). The number of depressive symptoms can be used as an index of greater illness burden in clinical psychiatry.

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