Types of Depression:

For some people, depression can be intense and occur in bouts that last for weeks at a time. For others, depression can be less severe but can linger at a low level for years.
Doctors who treat depression distinguish between these two types of depression. They call the more severe, short-lasting type major depression and the longer-lasting but less severe form dysthymia (pronounced: diss-thy-me-uh).
A third form of depression that doctors may diagnose is called adjustment disorder with depressed mood. This diagnosis refers to a depressive reaction to a specific life event (such as a death, divorce, or other loss), when adjusting to the loss takes longer than the normally expected timeframe or is more severe than expected and interferes with the person's daily activities.
Bipolar disorder (also sometimes called manic depressive illness) is another depressive condition that involves periods of major depression mixed with periods of mania. Mania is the term for abnormally high mood and extreme bursts of unusual activity or energy.