Major depressive disorder and persistent depressive disorder are two of the most common types of depression that people experience, however, there are many types of depression. What most mood disorders have in common are major depressive episodes. This is also true of bipolar disorder, another type of mood disorder.
Major Depressive Disorder
People who have major depressive disorder have had at least one major depressive episode (five or more symptoms for at least a two-week period). For some people, this disorder is recurrent, which means they may experience episodes once a month, once a year, or several times throughout their lives. People with recurrent episodes of major depression are sometimes said to have unipolar depression (or what used to be called “clinical depression”), because they only experience periods of low, or depressed mood.
Persistent Depressive Disorder
Persistent depressive disorder (formerly dysthymia) is a continuous long-term, chronic state of low-level depressed mood. The depressed state of persistent depressive disorder is not as severe as with major depression, but can be just as disabling.
Postpartum depression is characterized by feelings of sadness, indifference, exhaustion, and anxiety that a woman may experience after the birth of her baby. It affects one in every 9 women who have had a child, and can affect any woman, regardless of her age, race, or economic background.
People diagnosed with bipolar disorder have mood swings involving both lows (bipolar depression) and highs (called mania if severe or hypomania if mild). When people experience the lows of bipolar disorder (bipolar depression), their symptoms are very similar to those that someone with unipolar depression might experience.
Seasonal Affective Disorder
Seasonal Affective Disorder (SAD) typically starts in the late fall and early winter and dissipates during the spring and summer. Depressive episodes linked to the summer can occur, but are much less common than winter episodes of SAD.
Psychotic depression occurs when psychotic features such as hallucinations and delusions are accompanied by a major depressive episode, though psychotic symptoms generally have a depressive theme such as guilt, worthlessness, and death.