Associated descriptive features and mental disorders. Major Depressive Disorder is associated with high mortality. Up to 15% of individuals with severe Major Depressive Disorder die by suicide. Epidemiological evidence also suggests that there is a fourfold increase in death rates in individuals with Major Depressive Disorder who are over age 55 years. Individuals with Major Depressive Disorder admitted to nursing homes may have a markedly increased likelihood of death in the first year. Among individuals seen in general medical settings, those with Major Depressive Disorder have more pain and physical illness and decreased physical, social, and role functioning.
Major Depressive Disorder may be preceded by Dysthymic Disorder (10% in epidemiological samples and 15%-25% in clinical samples). It is also estimated that each year approximately 10% of individuals with Dysthymic Disorder alone will go on to have a first Major Depressive Episode. Other mental disorders frequently co-occur with Major Depressive Disorder (e.g., Substance-Related Disorders, Panic Disorder, Obsessive-Compulsive Disorder, Anorexia Nervosa, Bulimia Nervosa, Borderline Personality Disorder).
Associated laboratory findings. The laboratory abnormalities that are associated with Major Depressive Disorder are those associated with Major Depressive Episode. None of these findings are diagnostic of Major Depressive Disorder, but they have been noted to be abnormal in groups of individuals with Major Depressive Disorder compared with control subjects. Neurobiological disturbances such as elevated glucocorticoid levels and EEG sleep alterations are more prevalent among individuals with Psychotic Features and those with more severe episodes or with Melancholic Features. Most laboratory abnormalities are state dependent (i.e., are present only when depressive symptoms are present). However, evidence suggests that some sleep EEG abnormalities persist into clinical remission or may precede the onset of the Major Depressive Episode.
Associated physical examination findings and general medical conditions. Individuals with chronic or severe general medical conditions are at increased risk to develop Major Depressive Disorder. Up to 20%-25% of individuals with certain general medical conditions (e.g., diabetes, myocardial infarction, carcinomas, stroke) will develop Major Depressive Disorder during the course of their general medical condition. The management of the general medical condition is more complex and the prognosis is less favorable if Major Depressive Disorder is present. In addition, the prognosis of Major Depressive Disorder is adversely affected (e.g., longer episodes or poorer responses to treatment) by concomitant chronic general medical conditions.