Depression represents a combination of a negative mood state and physical changes that persist everyday for at least two weeks.

 Depressive symptoms usually develop over several weeks, although some sufferers may experience milder symptoms of the disease for months before their condition results in a full Major Depression.

Untreated, Major Depression can last six to 12 months, with 40 percent of individuals still having symptoms sufficient to meet the diagnosis after one year.

More than 85 to 90 percent of people with depression can be treated effectively. In most cases, an individual eventually will experience a complete remission of symptoms. However, approximately 25 to 33 percent of those untreated will continue to have some symptoms and associated difficulty with daily life that can linger for months or years.

Some people may only have a single episode of depression. However, more than 50 percent of those affected will experience another episode termed recurrent depression. Left untreated, this represents a chronic disease, with each episode increasing the risk for another bout of the disease. Seventy percent of those who have two episodes can expect to have a third, while 90 percent of individuals experiencing three episodes will have a fourth episode.