What Causes Depression?

The precise cause of depression is not known, but evidence points to several factors, including:

• Heredity
  
• Biochemical makeup
  
• Psychological makeup
  
• Stressful life events
  
• Fluctuating hormone levels
  
• Other factors such as general medical conditions and certain medications
  

Heredity

Depression does "run in families." People with a close relative who has had major depression or bipolar disorder are twice as likely to develop depression themselves.

Biochemical Makeup

Every human being has a unique biochemical makeup. Whether or not a person will experience depression (or other neurological disorders) depends largely on the amount of certain brain chemicals and how they interact in the central nervous system (CNS).

A person's biochemistry is an intricate balancing act. Think of a choreographed ballet with a troupe of dancers performing at once. If one or more of the dancers are out of step, the whole production is thrown off balance. So it is with an individual's biochemistry.

The brain is the "master" control center that governs our lives in every conceivable way. Just as messages from the brain (in the form of electrical impulses) control our movements, other messages control our emotions.

• Neurons, or nerve cells, are the most basic units in the brain. Neurons are separated by gaps called synapses.
  
• Chemical substances called neurotransmitters carry messages or signals across these gaps to various nerve cells.
  
• If there is a deficiency or an imbalance in certain neurotransmitters, a variety of disorders can result.
  
• The neurotransmitters serotonin, dopamine, and norepinephrine are the chemical messengers believed to be responsible for moods and emotions. Serotonin, in particular, has been implicated in depression. It is believed that a deficiency in the brain of the chemical messenger serotonin - or a disruption in the way it is able to perform its actions as a chemical messenger - has a profound negative effect on mood and emotions.
  

Psychological Makeup

It is said that a person's basic personality traits are often defined in early childhood. One defining factor is the social environment to which we are exposed. What happens to us in childhood can have a deep-rooted effect on our attitudes and behaviors in adulthood. For instance: