WHAT CAUSES DEPRESSION?

Depression has many causes. Often it's triggered not by a single factor but by a combination of factors, such as genetic vulnerability, stress, or changes in brain chemistry:

• Biochemistry - Disturbances in chemicals in the brain, like serotonin and norepinephrine, are thought to be connected to certain symptoms of depression, including anxiety, irritability and fatigue. Brain cells are designed to produce optimal levels of neurotransmitters to keep senses, learning, movements, and moods perking along. But in some people who are severely depressed or manic, the complex systems that accomplish this go awry. For example, receptors may be oversensitive or insensitive to a specific neurotransmitter, causing their response to its release to be excessive or inadequate.
  
• Genetics - Depression runs in families. For example, if one identical twin has depression, the other twin has 70% change of also having the illness sometime in life. Thus far, experts say genes alone are not known to trigger bipolar disorder or any form of depression. Rather, these illnesses probably result when genetic variations that create vulnerability are amplified by environmental factors, including early losses or chronic stress.
  
• Thinking Patterns - How resilient you are in the face of difficult life events, such as a job loss or divorce, may depend partly on your temperament and view of the world. Temperament-for example, how excitable you are or whether you tend to withdraw from or engage in social situations-certainly helps dictate behavior. People with low self-esteem, who are easily overwhelmed by stress, or who are generally pessimistic appear to be more vulnerable to depression.
  
• Environmental Factors - Repeated exposure to violence, neglect, poverty or physical, sexual or mental abuse may make people who are already susceptible to depression all the more vulnerable to the illness. When an individual is unaware of the wellspring of his or her illness, he or she can't easily move past the depression. Moreover, unless the person gains a conscious understanding of the source of the condition, later losses or disappointments may trigger its return.
  
• Other Medical Conditions - People with chronic illnesses such as asthma, diabetes, cancer, stroke, chronic pain, alcoholism or other drug disorders, heart disease or HIV are at higher risk for depression. There is no doubt that the stress of having certain illnesses-diabetes or cancer, for example-can trigger depression. In other cases, depression precedes the medical illness and may even contribute to it. To find out whether the mood changes occurred on their own or as a result of the medical illness, a doctor carefully considers a person's medical history and the results of a physical exam.
  
• The Birth of a Baby - Although getting the "blues" is common among new mothers, symptoms that are prolonged or severe may indicate postpartum depression. Please see the section on Postpartum Depression for further information.