There are many causes of depression and some people become depressed for a combination of reasons. For others, a single cause appears to trigger depression. Some become depressed for no apparent reason. Long-term or sudden illnesses can bring on or aggravate depression. It's important to recognize that depression often is a reaction to illness, especially one that produces chronic pain, disability and dependence.
Some medicines cause depressive symptoms as side effects.
Certain drugs used to treat high blood pressure and arthritis fall in this category. In addition, different drugs can interact in unforeseen ways when taken together. It's important that each doctor knows all the different types and dosages of medicine taken and discusses them with the patient. Genetics and family history. Depression runs in families and children of depressed parents have a higher risk of being depressed themselves.