Major depressive disorder or MDD refers to a mood disorder in which the person is suffering from one or more intense episodes of depression.

Major depressive disorder is also defined as a psychological disorder in which a person will have experienced five (5) or more of the following symptoms for at least 2 weeks:

  1. depressed mood or irritable mood most of the day; .
  2. decreased interest in pleasurable activities; .
  3. changes in weight, or perhaps failure to make necessary weight gains in adolescence; .
  4. sleep problems; .
  5. psychomotor agitation or retardation; .
  6. fatigue or loss of energy; .
  7. feelings of worthlessness or abnormal amounts of guilt;.
  8. reduced concentration and decision-making ability ; and
  9. repeated suicidal ideation, attempts, or plans of suicide.

Other definition

Major Depressive Disorder (Unipolar Depression) is in the Category of Mood Disorders.

Etiology Research has shown that depression is influenced by both biological and environmental factors.

Studies show that first degree relatives of people with depression have a higher incidence of the illness, whether they are raised with this relative or not, supporting the influence of biological factors. Situational factors, if nothing else, can exacerbate a depressive disorder in significant ways.

Examples of these factors would include lack of a support system, stress, illness in self or loved one, legal difficulties, financial struggles, and job problems. These factors can be cyclical in that they can worsen the symptoms and act as symptoms themselves.


Symptoms of depression include the following:

  • depressed mood (such as feelings of sadness or emptiness)
  • reduced interest in activities that used to be enjoyed, sleep disturbances (either not being able to sleep well or sleeping to much)
  • loss of energy or a significant reduction in energy level
  • difficulty concentrating, holding a conversation, paying attention, or making decisions that used to be made fairly easily
  • suicidal thoughts or intentions.


Treatment can either combine both pharmacotherapy and psychotherapy or utilize one or the other individually. Medications used to treat this disorder include Prozac, Paxil, Wellbutrin, and Zoloft. Other medications can be found, along with their descriptions can be found in the Medications page. Psychotherapy is useful in helping the patient understand the factors involved in either creating or exacerbating the depressive symptomotology. Personal factors may include a history of abuse (physical, emotional, and/or sexual), maladaptive coping skills/ Environmental factors involved in this disorder include, among others, a poor social support system and difficulties related to finances or employment. Prognosis Major Depressive Disorder has a better prognosis than other mood disorders in that medication and therapy have been very successful in alleviating symptomotology.

However, many people with this disorder find that it can be episodic, in that periodic stressors can bring back symptoms. In this case, it is often helpful to have an ongoing relationship with a mental health professional just as you would a physician if you had diabetes or high blood pressure.

Other /More definition:

A Major depressive disorder (MDD ) refers to a form of depressive disorder characterized by one or more major depressive episodes that last for at least 2 weeks and are accompanied by additional symptoms such as sleep disturbances or thoughts of suicide.