What is depression?
More than 20 million people in the United States experience depression, feeling "down" and "low" or "hopeless" for weeks at a time.  It's important to understand that depression is a clinical illness that affects the brain; it's not something made up in the head.  Depression is not simply a passing sadness or blue mood that lifts in a few hours or days, but is persistent.  Symptoms can persist and interfere with your everyday life.

Depressive illnesses are disorders of the brain. MRIs show that the brains of people who have depression look different than those of people without depression. In clinically depressed people, the parts of the brain responsible for regulating mood, thinking, sleep, appetite and behavior don't work normally.  Plus, researchers have found that the chemicals brain cells use to communicate appear to be out of balance in the brains of someone who is clinically depressed.

Types of depression
Several types of depressive disorders exist and can diagnosed. Some forms of depressive disorder may develop under unique circumstances. Dysthmic disorder and major depressive disorder are the most common forms of depression. Bipolar disorder, a mental illness characterized by bouts of depression, is not as common as major depression or dysthymia. We outline the common forms of depressions and their characteristics here:

Dysthymic disorder – Dysthymic disorder is characterized by long term (2+ years), less severe symptoms of depression that prevent normal everyday functioning or feeling well. People diagnosed with dysthymia may not be disabled by depression, but can experience one or more episodes of major depression.

Major depressive disorder-  Major depression is characterized by a combination of symptoms that interfere with a person's ability to live normally. Major depression is disabling and prevents a person from functioning normally. An episode of major depression may occur only once in a person's lifetime, but more often, it recurs throughout a person's life.

Psychotic depression – Psychotic depression is characterized as a severe depressive illness that is accompanied by psychosis, such as a break with reality, hallucinations, and delusions.

Postpartum depression – Post partum depression is diagnosed if a new mother develops a major depressive episode within one month after delivery. A fairly common type of depression , postpartum depression is diagnosed in about 10 to 15 % of women after they give birth.

Seasonal affective disorder (SAD) - SAD is a depressive illness experienced during the winter months. The depression generally lifts during spring and summer during times of more natural sunlight.

Is there one single cause of depression?  And are you more at risk of developing depression than someone else?  Click here for more information about risk factors and causes of depression.