A mood disorder characterized by a period of at least 2 weeks of depressed mood, or the loss of interest or pleasure in nearly all activities.

In general, the relationships of several factors contribute to mood disorders. The most significant contributing factor is heredity. However, the exact means of inheritance is unknown. Other factors include, childhood loss of parent, and stressors (e.g., traumatic life event's and persons with introverted, anxious temperaments). In addition, being female may be a predisposing factor as well as the development of the condition secondary to another physiologic or psychologic disorder. It is often preceded by a dysthymic disorder (see Diagnostic Code: 9433 Dysthymic disorder).

Major depressive disorder is associated with a relatively high mortality rate. It has been reported that up to 15% of persons experiencing this disorder die from suicide. Patients diagnosed with this disorder, exhibit at least four of the following characteristics: changes in appetite, weight, sleep patterns, or psychomotor activity; decreased energy; feelings of worthlessness or guilt; difficulty thinking, concentrating, or making decisions; and recurrent thoughts of death, plans for death, or attempts to commit suicide.

Diagnostic criteria for this disorder are as follows:

• Single Episodes:

  • Occurrence of one major depressive episode.

  • The episode is not better associated with schizoaffective disorder, and does not apply to schizophreniform disorder, delusional disorder, or psychotic disorder not otherwise specified

  • There has never been a manic episode, mixed episode, or hypomanic episode that can be attributed to causes other than substance abuse or treatments.

• Recurrent Episodes:

  • Occurrence of two or more major depressive episodes (should be a successive two-month time period between episodes).

  • The episode is not better associated with schizoaffective disorder, and does not apply to schizophreniform disorder, delusional disorder, or psychotic disorder not otherwise specified.

  • There has never been a manic episode, mixed episode, or hypomanic episode that can be attributed to causes other than substance abuse or treatments.

Medications, supportive therapy, and psycho-education are usually indicated in the treatment of moderate to severe depression. All patients should be assessed for suicidal ideation, plans, or activity. All indications of self-destruction should be taken seriously. If treated with medications, administration should continue for at least the time the episode lasts.

Major depressive episodes may end totally, partially, or not at all. In patients with partial recovery, there is a greater chance of developing additional episodes, and they continue on a course of periodic episodes. Research studies suggest that 1 year after diagnosis of this disorder, 40% of patients still have episodes that are characteristic of a full major depressive disorder, 20% still have some symptoms, and 40% have no mood disorder.