Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Depression Health Center

Font Size

Understanding Depression -- the Basics

What Are the Different Types of Depression? continued...

Major depression, which affects more than 16% of U.S. adults over a lifetime, often appears spontaneously and is seemingly unprovoked, or it can begin as a depressive reaction following a loss, trauma, or other significant stressful event. In people who are biologically predisposed to developing a depressive illness, the initial depressive reaction can intensify and evolve into a clinically full-blown depressive episode. The depressive episode may also disappear spontaneously, usually within six to 12 months, although medication as well as other forms of treatment are often needed to achieve full control of symptoms. Because of its disabling effects and the possibility of suicide, major depression often requires medical treatment.

  • Dysthymia . A low-grade, long-term depression that lasts for more than one year for children and adolescents and at least two years for adults. Dysthymia involves fewer symptoms than occur in a major depressive episode, but it is persistent and longstanding and often can be as disabling as major depression. Over the course of a lifetime, over 11% of teens (13-18) suffer from dysthymia, according to the National Institute of Mental Health. In modern diagnostic terminology, dysthymia together with chronic major depression (that is, a major depressive episode lasting two years or longer) are both included under the category of "persistent depressive disorder."

What Causes Depression?

No one knows exactly what causes depression, although it appears to be an illness that may result from the interplay of many biological and environmental factors. Depressive reactions, which can involve sad mood but not the physical signs and symptoms of a major depressive episode, occur as a result of a particular event. Depressed moods can also be a side effect of medication, hormonal changes (such as before menstrual periods or after childbirth), or a physical illness, such as the flu or a viral infection. Clinical depression involves a syndrome of many physical and emotional or behavioral symptoms that can occur for no apparent reason in people who are biologically vulnerable to the disorder.

Although the exact causes of major depression and dysthymia are unknown, researchers currently believe that both of these forms of depression are caused by a malfunction of brain circuits that regulate mood, thinking and behavior. Brain chemicals called neurotransmitters (such as serotonin, norepinephrine and dopamine) are important for healthy nerve cell connections; medicines that can regulate levels of these chemicals can help to fine-tune the efficiency of how these brain circuits function.

Today on WebMD

Differences between feeling depressed and feeling blue.
jk rowling
Famous people who've struggled with persistent sadness.
depressed man sitting on hallway floor
Learn the truth about this serious illness.
Sad woman looking out of the window
Tips to stay the treatment course.
unhappy teen boy
Health Check
jk rowling
Pills with smiley faces
Teen girl huddled outside house
Depressed man sitting in hospital hallway
antidepressants slideshow
pill bottle
Winding path