Mental illness' is a general term that refers to a group of illnesses, in the same way that heart disease refers to a group of illnesses affecting the heart. Episodes of a mental illness can come and go in periods through people's lives.
Some people experience their illness only once and fully recover.
For others, it recurs throughout their lives. Most mental illnesses can be effectively treated. Though we know that many mental illnesses are caused by a physical dysfunction of the brain, we do not know exactly what triggers this. Stress may trigger some mental illnesses or may prolong episodes. Stress can also result when a person develops a mental illness.