Subtypes of Depression

There are three major medical classifications of depression. First, unipolar depression, where the patient’s mood swings in only in one direction, downward, is distinguished from bipolar or manic depression where patients experience both extreme highs and extreme lows. The second, and probably less helpful distinction, is endogenous (biological) versus reactive (environmental) depression. The third category is primary depression where depression is viewed as the major illness verses secondary depression which is caused by another illness such as an infection, endocrine disorder, or postpartum physiology.

Unipolar Depression. DSM-IV¹⁴ subdivides unipolar depression into three subtypes, Major Depressive Episode, Dysthymic Disorder, and Depressive Disorder NOS (Not Otherwise Specificed). A Major Depressive Episode occurs when the symptoms listed above are present for at least two weeks. The key word is episode, because “this type of depression is seen to be cyclical, episodic, and interspersed with periods of normal mental health.”¹⁵ If untreated, an episode will last an average 9 months and 50% of depressive episodes will reoccur. After three or more episodes, the odds of reoccurrence within three years increases to 70-80% if the patient has not received preventative treatment.¹⁶

Dysthymia is a relatively new classification of depression is alternatively called minor depression or chronic depression. It is distinguished by “a history of depressed mood more days than not for at least two years, but which did not originate with a major depressive episode.”¹⁷

Bipolar Disorder. Bipolar disorders are subdivided into a parallel set of three subtypes: Bipolar disorder, Cyclothymia, and Bipolar disorder NOS (Not Otherwise Specified).

Bipolar disorder, or manic depression as it used to be called, affects fewer people and is only diagnosed in 5-10% of people with depression. In addition to the melancholic symptoms of unipolar depression, those with bipolar depression also experience alternating episodes of mania which include psychological (euphoric mood, flights of ideas, heightened self-esteem, delusions and grandiose thoughts, and excessive, impulsive, or uninhibited behavior) and physical symptoms (rapid speech, reduced need for sleep, and excessive appetite).

Cyclothymia is similar to dysthymia in that it is a less severe form of bipolar disorder that occurs over a longer period of time. Patients have bouts of depression and hypomania with alternate or interspersed periods of normal moods.

Bipolar depression can be alternately understood as a more severe form of depression in a continuum from unipolar to bipolar depression rather than as a distinct disease.