As an example, Hypothyroidism problem is one of the most problem that cause clinical depression. Many of the diseases associated with nervous system or central nerve injuries and various wounds may lead to emergence of disease clinical mental depression.
Clinical depression may shows in one of these factors:
Cancer in the central nervous system;
Head injuries;
MS (Multiple sclerosis);
Stroke;
Syphilis;
Different cancers (pancreas, prostate gland, chest).
There are remedies that reduce clinical mental depression, but you should visit the doctor to get the right drug.