Nearly 20 million American adults fall ill from depression each year--that's almost one-tenth of the entire adult population. This devastating condition is not to be ignored: it influences nearly every part of a person's life, from sleeping patterns to appetite to mindset to activities. And unlike a bad mood, which passes almost as quickly as it comes, depression is long-lasting condition that can persist over months or years.Sufferers from depression feel persistently sad, empty, hopeless, and restless. They are prone to irritability and get irked even by small problems. They may no longer enjoy activities they once loved, and they may oversleep in the morning or have trouble getting to bed at night. But the disease is not just mental. It can manifest itself in physical forms, too: chronic pain, digestive ailments, and even self-inflicted wounds. Also, doctors can actually see chemical and structural changes in the brains of people with major depression.

Depression can strike anyone, at any time. It may afflict the elderly, children, men or women, without regard to race, age, gender or background. However, there is some evidence to suggest that the condition may be genetic, especially with severe disorders such as manic-depressive disorder. But it is critical to note that genetic disposition does not automatically cause the disease. Often, external factors (such as stress, life-altering events, trauma, and so on) can trigger a latent potential condition.

It's important to recognize that depression doesn't just come in one form, and doesn't have just one set of symptoms. Like any other category of diseases, like cancer or heart problems, depression is a heading that covers many individual conditions. You may have heard of some of the more well-known types. Bipolar disorder, or manic-depression, is a relatively rare but dangerous condition in which a patient has dramatic mood swings between "mania" and a severe depressed state. Major depression is a long-term condition that is characterized by such symptoms as inability to concentrate, not wanting to take part in pleasurable activities, feeling tired or unenergetic, and being unable to complete work or make decisions. A less severe but more prolonged form of the disease, dysthymia, involves lower-grade but chronic symptoms that interfere with quality of life while not completely disabling the sufferer.Depression can have devastating consequences, both for the sufferer and his or her friends and family, but fortunately it is a treatable condition. Of the 20 million adults who suffer from depression, some cases are severe and require intensive treatment and intervention, but most can be more readily treated and the harmful effects of the disease alleviated. Many people with depression are hesitant to seek out professional help, but it is important to know that your symptoms are treatable. Doctors and psychologists have a great deal of experience using medication and therapy in combination to produce very effective results and greatly improve the quality of life for people with depressive disorder. Learn more about depression and how to get help in Depression: Part 2