Depression Causes

The exact cause of depression is not known. Depression may be caused by:

• A family history
• Alcohol or drug abuse
• Childhood incidents (abuse or neglect)
• Chronic medical conditions (brain tumor, cancer, diabetes, heart disease, hormone disorders, hypothyroidism, Parkinson's disease, or stroke)
• Chronic pain
• Disappointments or stress at home, work, or school
• Long-term use of certain medications (high blood pressure, sedatives, or sleeping pills)
• Loss of a loved one, employment, valuables, or home
• Nutritional deficiencies (the B vitamin folate or omega-3 fatty acids)
• Personality (dependent, low self-esteem, negative, pessimistic, self-critical, stressed, or worried)
• Sleeping problems
• Social isolation
• Trauma

Some types of depression run in families, which may be due to:

• Genetics
• Learned behaviors in childhood

Scientists believe that a genetic predisposition combined with certain environmental factors (such as stress or a medical condition) make some people more likely to become depressed. Despite this connection, not everyone with a genetic predisposition develops depression, while some people without a family history become depressed. Researchers are searching for the genes associated with depression. Several genes associated with bipolar disorder have already been identified.

There also appears to be a biochemical link to depression. Neurotransmitters are brain chemicals that carry messages between the brain's nerve cells (neurons). Abnormal levels of the neurotransmitters serotonin, norepinephrine, and dopamine in areas of the brain that control mood and emotion are associated with depression. The exact nature of the relationship between these neurotransmitters and depression is not yet fully understood. It's not clear whether abnormal levels of these neurotransmitters cause depression or are the result of depression.