Persons with Major Depressive Disorder experience, at least, a two week period of suffering either a depressed mood or the loss of interest or pleasure in nearly all activities.  In addition, at least four of the following must be met:

• Change in appetite or weight
• Change in sleep
• Decreased energy
• Feelings of worthlessness or guilt
• Difficulties in concentrating
• Psychomotor changes (agitation, lethargy)
• Recurrent thoughts of death or suicidal ideation, plan, or intent

There is also impairment in social, occupational, and other important areas of functioning in one’s life.  In general, individuals feel “down in the dumps”, “sad”, “hopeless”, etc.  In children and adolescents, an irritable mood may be present as opposed to sadness.  Studies indicate that depressive episodes occur twice as much in women than in men.

American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, Fourth  Edition, text Revision. Washington, DC American Psychiatric Association, 2000.