Major Depression (Clinical Depression)

Full description of major depression (clinical depression, major depressive disorder). Definition, signs, symptoms, causes of major depression.

Full description of major depression (clinical depression, major depressive disorder). Definition, signs, symptoms, and causes of major depression.

Description of Major Depression

Major depression is also known as clinical depression and major depressive disorder. This serious medical illness affects some 15 million American adults every year or about 5-8% of the adult population. Women are nearly twice as likely than men to develop major depression, although researchers don't know the reason why.

Severe sadness, along with feeling worthless, hopeless, and helpless over a prolonged period of time are some of the hallmark symptoms of major depression. These symptoms interfere with a person's ability to work, sleep, study, eat, and enjoy once-pleasurable activities. Major depression is disabling and prevents a person from functioning normally. The Merck Manual notes that In some patients, "depressed mood is so deep that tears dry up; they report that they are unable to experience usual emotions and feel that the world has become colorless and lifeless." Nutrition may be severely impaired, requiring immediate intervention. Some depressed patients neglect personal hygiene or even their children, other loved ones, or pets. Many with major depression consider suicide as a serious option.

An episode of major depression may occur only once in a person's lifetime, but more often, it recurs throughout a person's life.

Major depression is often divided into subgroups.

  • The psychotic subgroup is characterized by delusions, often of having committed unpardonable sins or crimes, harboring incurable or shameful disorders, or of being persecuted. Patients may have auditory or visual hallucinations (eg, accusatory or condemning voices).
  • The catatonic subgroup is characterized by severe psychomotor retardation or excessive purposeless activity, withdrawal, and, in some patients, grimacing and mimicry of speech (echolalia) or movement (echopraxia).
  • The melancholic subgroup is characterized by loss of pleasure in nearly all activities, inability to respond to pleasurable stimuli, unchanging emotional expression, excessive or inappropriate guilt, early morning awakening, marked psychomotor retardation or agitation, and significant anorexia or weight loss.
  • The atypical subgroup is characterized by a brightened mood in response to positive events and rejection sensitivity, resulting in depressed overreaction to perceived criticism or rejection, feelings of leaden paralysis or anergy, weight gain or increased appetite, and hypersomnia.

Diagnostic Criteria for Major Depression

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. (Note: Do not include symptoms that are clearly due to a general medical condition, or mood-incongruent delusions or hallucinations.)

  • depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g., feels sad or empty) or observation made by others (e.g., appears tearful). Note: In children and adolescents, can be irritable mood.
  • markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (as indicated by either subjective account or observation made by others)
  • 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. Note: In children, consider failure to make expected weight gains.
  • insomnia or hypersomnia nearly every day
  • psychomotor agitation or retardation nearly every day (observable by others, not merely subjective feelings of restlessness or being slowed down)
  • fatigue or loss of energy nearly every day
  • feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day (not merely self-reproach or guilt about being sick)
  • diminished ability to think or concentrate, or indecisiveness, nearly every day (either by subjective account or as observed by others)
  • 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

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

The symptoms are not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition (e.g., hypothyroidism).

The symptoms are not better accounted for by bereavement, i.e., after the loss of a loved one, the symptoms persist for longer than 2 months or are characterized by marked functional impairment, morbid preoccupation with worthlessness, suicidal ideation, psychotic symptoms, or psychomotor retardation.

Causes of Major Depression

There's no single cause of major depression. Researchers have discovered a strong genetic predisposition to major depression, where the illness can run in families with a history of depression.

As with many mental illnesses, scientists believe a combination of genetics, biology, environmental and psychological factors play a role in the development of major depressive disorder. Life events, such as the death of a loved one, a major loss or change, chronic stress, and alcohol and drug abuse, may trigger episodes of depression. People who are introverted and who have anxious tendencies may be more likely to develop a depressive disorder. Such people often lack the social skills to adjust to life pressures. Depression may also develop in people with other psychological disorders. Some illnesses such as heart disease and cancer and some medications may also trigger depressive episodes. It is also important to note that many depressive episodes occur spontaneously and are not triggered by a life crisis, physical illness, or other risk factors.

For comprehensive information on major depression (clinical depression) and other forms of depression, visit the Depression Community.

Sources: 1. American Psychiatric Association. (1994). Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition. Washington, DC: American Psychiatric Association. 2. Merck Manual, Home Edition for Patients and Caregivers, last revised 2006. 3. National Institute of Mental Health website, "About Depression."

APA Reference
Writer, H. (2009, January 2). Major Depression (Clinical Depression), HealthyPlace. Retrieved on 2019, September 16 from

Last Updated: July 5, 2019

Medically reviewed by Harry Croft, MD

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