Eating and sleeping patterns can be exaggerated to either extreme, either excessive or almost eliminated. Observable or behavioral symptoms may be minimal despite profound inner turmoil. Depression is a holistic disorder, generally affecting body, feelings, thoughts, and behaviors to varying degrees. To establish the diagnosis of major depression, a patient must express one of the first 2 and at least 5 of the other symptoms listed above. Such disturbances must be present nearly daily for at least 2 weeks.
Symptoms can last for months or years.
Symptoms can cause significant personality changes and changes in work habits, making it difficult for others to empathize with the depressed individual. Some symptoms are so disabling that they interfere significantly with the patient's ability to function. In very severe cases, people with depression may be unable to eat or even to get out of bed. Clinical depression commonly occurs concurrently with other medical illnesses and worsens the prognosis for these illnesses. Even diagnosis of concurrent illness is made much more difficult by the presence of depression.