What Is Depression?

Depression comes under the umbrella of mood or affective disorders, in which individuals have difficulty controlling mood states. The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5; American Psychiatric Association, 2013) categorizes depressive disorders principally as follows:

  • Disruptive Mood Dysregulation Disorder
  • Major Depressive Disorder
  • Persistent Depressive Disorder (Dysthymia)
  • Premenstrual Dysphoric Disorder
  • Substance/Medication-Induced Depressive Disorder

The manual also considers depressive states arising from medical conditions such as stroke, traumatic brain injury, Parkinson’s disease, and others, with two further categories covering other specified and unspecified depressive disorders (American Psychiatric Association, 2013).

Depression is marked by a deep sense of sadness and reduced motivation and activity levels. Most people suffering a bout of major depression experience a recovery phase—within 3 months for 40% of sufferers, and within a year for 80%. But some suffer chronic depression (dysthymia) that persists for years (American Psychiatric Association, 2013). Factors that influence risk and prognosis are temperament, environmental factors such as adverse childhood experiences and stressful life events, genetics, and physiological factors. According to the World Health Organization, depression affects an estimated 350 million people globally (WHO, 2016).

Major Depressive Disorder Diagnostic Criteria (abbreviated from the DSM–5)

A. Five (or more) of the following symptoms have been present during the same 2-week period and represent a
change from previous functioning; at least one of the symptoms is either (1) depressed mood or (2) loss of
interest or pleasure.

  1. Depressed mood most of the day, nearly every day, as indicated by either subjective report or observation made by others.
  2. Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day.
  3. Significant weight loss when not dieting or weight gain (e.g., a change of more than 5% of body weight in a month), or decrease or increase in appetite nearly every day.
  4. Insomnia or hypersomnia nearly every day.
  5. Psychomotor agitation or retardation nearly every day (observable by others).
  6. Fatigue or loss of energy nearly every day.
  7. Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day.
  8. Diminished ability to think or concentrate, or indecisiveness, nearly every day.
  9. Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide.

B. The symptoms cause clinically significant distress or impairment in social, occupational, or other important
areas of functioning.

C. The episode is not attributed to the physiological effects of a substance or to another medical condition.

D. The occurrence of the major depressive episode is not better explained by schizoaffective disorder,
schizophrenia, schizophreniform disorder, delusional disorder, or other specified and unspecified
schizophrenia spectrum and other psychotic disorders.

E. There has never been a manic episode or a hypomanic episode.
(American Psychiatric Association, 2013)


Some Brain Areas Involved in Depression

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The Neurobiology of Depression – Reading Course for The Science of Psychotherapy Standard Members