Depression is a serious medical condition. In contrast to the normal emotional experiences of sadness, loss, or
passing mood states, clinical depression is persistent and can interfere significantly with an individual's ability to
function. There are three main types of depressive disorders: major depressive disorder, dysthymic disorder, and
bipolar disorder (manic-depressive illness).

Symptoms and Types of Depression
Symptoms of depression include sad mood, loss of interest or pleasure in activities that were once enjoyed, change in
appetite or weight, difficulty sleeping or oversleeping, physical slowing or agitation, energy loss, feelings of
worthlessness or inappropriate guilt, difficulty thinking or concentrating, and recurrent thoughts of death or
suicide. A diagnosis of major depressive disorder is made if a person has 5 or more of these symptoms and impairment
in usual functioning nearly every day during the same two-week period. Major depression often begins between ages 15
to 30 but also can appear in children. Episodes typically recur.

Some people have a chronic but less severe form of depression, called dysthymic disorder, which is diagnosed when
depressed mood persists for at least 2 years (1 year in children) and is accompanied by at least 2 other symptoms of
depression. Many people with dysthymia develop major depressive episodes.

Episodes of depression also occur in people with bipolar disorder. In this disorder, depression alternates with
mania, which is characterized by abnormally and persistently elevated mood or irritability and symptoms including
overly-inflated self-esteem, decreased need for sleep, increased talkativeness, racing thoughts, distractibility,
physical agitation, and excessive risk taking. Because bipolar disorder requires different treatment than major
depressive disorder or dysthymia, obtaining an accurate diagnosis is extremely important.

Facts About Depression
Major depression is the leading cause of disability in the U.S. and worldwide.
Depressive disorders affect an estimated 9.5 percent of adult Americans ages 18 and over in a given year, 3 or about
18.8 million people in 1998.
Nearly twice as many women (12 percent) as men (7 percent) are affected by a depressive disorder each year.
Depression can be devastating to family relationships, friendships, and the ability to work or go to school. Many
people still believe that the emotional symptoms caused by depression are "not real," and that a person should be able
to shake off the symptoms. Because of these inaccurate beliefs, people with depression either may not recognize that
they have a treatable disorder or may be discouraged from seeking or staying on treatment due to feelings of shame and
stigma. Too often, untreated or inadequately treated depression is associated with suicide.

Treatments
Antidepressant medications are widely used, effective treatments for depression. 6 Existing antidepressants influence
the functioning of certain chemicals in the brain called neurotransmitters. The newer medications, such as the
selective serotonin reuptake inhibitors (SSRIs), tend to have fewer side effects than the older drugs, which include
tricyclic antidepressants (TCAs) and monoamine oxidase inhibitors (MAOIs). Although both generations of medications
are effective in relieving depression, some people will respond to one type of drug, but not another. Other types of
antidepressants are now in development.

Certain types of psychotherapy, specifically cognitive-behavioral therapy (CBT) and interpersonal therapy (IPT), have
been found helpful for depression. Research indicates that mild to moderate depression often can be treated
successfully with either therapy alone; however, severe depression appears more likely to respond to a combination of
psychotherapy and medication. 7 More than 80 percent of people with depressive disorders improve when they receive
appropriate treatment.

Research Findings
Brain imaging research is revealing that in depression, neural circuits responsible for moods, thinking, sleep,
appetite, and behavior fail to function properly, and that the regulation of critical neurotransmitters is impaired.

Genetics research, including studies of twins, indicates that genes play a role in depression. Vulnerability to
depression appears to result from the influence of multiple genes acting together with environmental factors.

Other research has shown that stressful life events, particularly in the form of loss such as the death of a close
family member, may trigger major depression in susceptible individuals.

The hypothalamic-pituitary-adrenal (HPA) axis, the hormonal system that regulates the body's response to stress, is
overactive in many people with depression. Research findings suggest that persistent overactivation of this system may
lay the groundwork for depression.

Studies of brain chemistry, mechanisms of action of antidepressant medications, and the cognitive distortions and
disturbed interpersonal relationships commonly associated with depression, continue to inform the development of new
and better treatments.