health

The causes of depression have been debated for decades, with researchers
disagreeing as to whether biology, psychology, or a combination of the
two offers the best explanation. Most researchers now think that depression
is the end result of biological vulnerability to a mood disorder combined
with personal history and certain personality traits.

• Genetic factors. No specific genes have been identified, although
  the disorder is known to run in families.
  
• Biochemical. Researchers have found that the brains of people
  with depression have abnormal levels of certain brain chemicals
  called neurotransmitters. Neurotransmitters relay impulses from
  one nerve cell to the next.
  
• Life history. Difficult circumstances early in life, too many traumatic
  experiences too close together, or high stress levels over a long
  period of time can all make people more likely to become depressed.
  
• Personality factors. People who are pessimistic, easily discouraged,
  or inclined to worry a lot are vulnerable to depression.

An occasional blue mood or temporary feeling of discouragement is not
a depression. For a diagnosis of depression a personmust have five symptoms
from the following list for at least two weeks. The symptomsmust be severe
enough to interfere with the person’s daily activities and relationships:

• Depressed mood
  
• Loss of interest or pleasure in activities that the person used to
  enjoy
  
• Weight gain or loss
  
• Difficulty sleeping or sleeping much more than usual
  
• Slowed movement or extreme restlessness
  
• Lack of energy; difficulty getting things done
  
• Feeling worthless or hopeless
  
• Problems with concentrating or decision making
  
• Thoughts of death or suicide