Impairment in major depression: implications for diagnosis

A significant change in the criteria for major depressive disorder in the DSM-IV over the earlier editions was the introduction of a criterion of "clinically significant distress and impairment" (criterion C). However, it is not clear that cases of depression which meet this criterion are distinct from cases that do not meet the criterion on characteristics beyond mere severity of illness. This report used data from the National Comorbidity Survey (NCS) to compare the psychiatric and sociodemographic characteristics of cases of DSM-III-R major depression with varying levels of self-rated impairment. The results of the analyses revealed no difference between respondents with different levels of impairment on gender, age of onset, parental history of depression and suicide, duration of illness, and symptom profiles. With regard to the social and psychiatric indicators of severity of illness, on the other hand, there was a gradient for worse outcome among more severely impaired respondents. It is concluded that the less impaired respondents with DSM-III-R major depression cannot be distinguished from the more impaired on illness characteristics that are not related to the severity of illness. Therefore, cases of DSM-III-R major depression with various levels of impairment most probably represent cases of the same illness that vary only in severity.