The development of major depressive disorder may be related to certain medical illnesses. As many as 20%-25% of those who have illnesses such as cancer, stroke, diabetes, and myocardial infarction are likely to develop major depressive disorder sometime during the presence of their medical illness. Managing or treating a medical condition can be more difficulty if a person is also clinically depressed. The prognosis for the medical problem may also be less positive.
It has been shown that other mental health conditions may often co-exist with major depressive disorder. Some of these are alcohol/drug abuse, anxiety and panic disorders, obsessive-compulsive disorder, eating disorders, and borderline personality disorder.
Major depressive disorder should be taken very seriously since up to 15% of those with this condition die by suicide.