1. At least one of the following three abnormal moods which significantly interfered with the person's life:
   
   
   1. Abnormal depressed mood most of the day, nearly every day, for at least 2 weeks.
      
      
   2. Abnormal loss of all interest and pleasure most of the day, nearly every day, for at least 2 weeks.
      
      
   3. If 18 or younger, abnormal irritable mood most of the day, nearly every day, for at least 2 weeks.
      
      
   
    
2. At least five of the following symptoms have been present during the same 2 week depressed period.
   
   
   1. Abnormal depressed mood (or irritable mood if a child or adolescent) [as defined in criterion A].
      
      
   2. Abnormal loss of all interest and pleasure [as defined in criterion A2].
      
      
   3. Appetite or weight disturbance, either:
      
      
      • Abnormal weight loss (when not dieting) or decrease in appetite.
      • Abnormal weight gain or increase in appetite.
      
       
   4. Sleep disturbance, either abnormal insomnia or abnormal hypersomnia.
      
      
   5. Activity disturbance, either abnormal agitation or abnormal slowing (observable by others).
      
      
   6. Abnormal fatigue or loss of energy.
      
      
   7. Abnormal self-reproach or inappropriate guilt.
      
      
   8. Abnormal poor concentration or indecisiveness.
      
      
   9. Abnormal morbid thoughts of death (not just fear of dying) or suicide.
   
    
3. The symptoms are not due to a mood-incongruent psychosis.
   
   
4. There has never been a Manic Episode, a Mixed Episode, or a Hypomanic Episode.
   
   
5. The symptoms are not due to physical illness, alcohol, medication, or street drugs.
   
   
6. The symptoms are not due to normal bereavement.
   
   

By definition, Major Depressive Disorder cannot be due to:

• Physical illness, alcohol, medication, or street drug use.
• Normal bereavement.
• Bipolar Disorder
• Mood-incongruent psychosis (e.g., Schizoaffective Disorder, Schizophrenia, Schizophreniform Disorder, Delusional Disorder, or Psychotic Disorder Not Otherwise Specified).

Major Depressive Disorder causes the following  mood  symptoms:

• Abnormal depressed mood:

  Sadness is usually a normal reaction to loss. However, in Major Depressive Disorder, sadness is abnormal because it:

  • Persists continuously for at least 2 weeks.
  • Causes marked functional impairment.
  • Causes disabling physical symptoms (e.g., disturbances in sleep, appetite, weight, energy, and psychomotor activity).
  • Causes disabling psychological symptoms (e.g., apathy, morbid preoccupation with worthlessness, suicidal ideation, or psychotic symptoms).

  The sadness in this disorder is often described as a depressed, hopeless, discouraged, "down in the dumps," "blah," or empty. This sadness may be denied at first. Many complain of bodily aches and pains, rather than admitting to their true feelings of sadness.

• Abnormal loss of interest and pleasure mood:
  
  
  • The loss of interest and pleasure in this disorder is a reduced capacity to experience pleasure which in its most extreme form is called anhedonia.
  • The resulting lack of motivation can be quite crippling.
  
   
• Abnormal irritable mood:
  
  
  • This disorder may present primarily with irritable, rather than depressed or apathetic mood. This is not officially recognized yet for adults, but it is recognized for children and adolescents.
  • Unfortunately, irritable depressed individuals often alienate their loved ones with their cranky mood and constant criticisms.

Major Depressive Disorder causes the following  physical  symptoms:

• Abnormal appetite: Most depressed patients experience loss of appetite and weight loss. The opposite, excessive eating and weight gain, occurs in a minority of depressed patients. Changes in weight can be significant.

• Abnormal sleep: Most depressed patients experience difficulty falling asleep, frequent awakenings during the night or very early morning awakening. The opposite, excessive sleeping, occurs in a minority of depressed patients.

• Fatigue or loss of energy: Profound fatigue and lack of energy usually is very prominent and disabling.

• Agitation or slowing: Psychomotor retardation (an actual physical slowing of speech, movement and thinking) or psychomotor agitation (observable pacing and physical restlessness) often are present in severe Major Depressive Disorder.

Major Depressive Disorder causes the following  cognitive  symptoms:

• Abnormal self-reproach or inappropriate guilt:
  
  
  • This disorder usually causes a marked lowering of self-esteem and self-confidence with increased thoughts of pessimism, hopelessness, and helplessness. In the extreme, the person may feel excessively and unreasonably guilty.
  • The "negative thinking" caused by depression can become extremely dangerous as it can eventually lead to extremely self-defeating or suicidal behavior.
  
   
• Abnormal poor concentration or indecisiveness:
  
  
  • Poor concentration is often an early symptom of this disorder. The depressed person quickly becomes mentally fatigued when asked to read, study, or solve complicated problems.
  • Marked forgetfulness often accompanies this disorder. As it worsens, this memory loss can be easily mistaken for early senility (dementia).
  
   
• Abnormal morbid thoughts of death (not just fear of dying) or suicide:
  
  
  • The symptom most highly correlated with suicidal behavior in depression is hopelessness.

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