Based on the duration of symptoms, timing, and the presumed etiologies, depressive disorders are classified into 7 subtypes: major depressive disorder, persistent depressive disorder (or dysthymia), premenstrual dysphoric disorder, substance/medication-induced depressive disorder, depressive disorder due to another medical condition, other specified depressive disorder, and unspecified depressive disorder.

• The common feature of all depressive disorders is the presence of dysphoric mood (i.e., sad, empty, or irritable mood), with accompanying somatic and cognitive symptoms that significantly affect the functional capacity of the individuals. Depressive disorders may be classified according to the duration, timing, and presumed etiologies into the following subtypes: ^[1]
  • Major depressive disorder: is characterized by single or discrete episodes of depressed mood (most of the day) and/or anhedonia and at least four other depressive symptoms that last at least for 2 weeks. All symptoms must be present nearly every day, except for thoughts of death or suicidal ideation/suicidal attempts.
  • Persistent depressive disorder (or dysthymia): Dysthymia is mild, chronic depression that lasts at least 2 years in adults and 1 year in children, and on most days, patients experience depressed mood for most of the day and at least two other symptoms of depression.
  • Premenstrual dysphoric disorder:This distinctive depressive condition is responsive to treatment. The depressive symptoms begin in the final week of the menstrual cycle and remit early in the menstrual phase. The characteristic symptoms include mood lability, irritability, anxiety, depressed mood, hopelessness, poor concentration, fatigue, changes in appetite and sleep, and physical symptoms (breast tenderness, swelling, and bloating).
  • Substance/medication-induced depressive disorder: This condition is characterized by a depressed mood that is due to a substance, for example, alcohol or medications (e.g. barbiturates).
  • Depressive disorder due to another medical condition:This condition is characterized by a depressed mood secondary to a medical disorder such as hypothyroidism, or Cushing’s syndrome.
  • Other specified depressive disorder: This diagnostic category includes two subtypes:
    • 1) Recurrent depressive episode: depression that lasts 2-13 days and occurs at least once a month
    • 2) Short-duration depressive episode: a depressed mood lasting 4-14 days, and is nonrecurrent
  • Unspecified depressive disorder: This diagnostic category includes 4 major subtypes:
    • 1) Melancholia: a severe form of depression characterized by anhedonia, hopelessness, and psychomotor retardation
    • 2) Atypical depression: is characterized by weight gain and hypersomnia
    • 3) Peripartum depression (previously called postpartum depression): The onset of symptoms is around parturition or within 4 weeks postpartum. These patients commonly have psychotic symptoms.
    • 4) Seasonal pattern (previously called seasonal affective disorder SAD): Patients with a seasonal pattern to their depressive symptoms tend to experience a depressed mood during a particular season, most commonly winter. These patients may preferentially respond to light therapy.
  • Disruptive mood dysregulation disorder: This disorder is characterized by frequent episodes of temper tantrums, persistent irritability, and angry mood in children 6-12 years of age.