More than one in 20 Americans has experienced major depression in the last 12 months and more than one in 10 has experienced the mental illness at some point in life, according to a new national survey.

The results show that for the first time, middle-aged baby boomers are more likely to have experienced depression than young adults, marking a major shift in depression age distribution.

Other groups more likely to report a history of depression include:

—Women

—Native Americans

—Widowed, separated, or divorced men and women

—Low-income individuals

Researchers also found that the average duration of a major depression episode was six months rather than the four months found in previous studies.

Major depression was defined as two or more weeks of persistent depressed mood accompanied by five or more symptoms of depression during that time, such as loss of interest in daily activities, changes in appetite, and feeling tired all the time.

Quiz: Could You Be Depressed?

Depression in the U.S.

Researchers say it’s the largest survey ever on depression and co-existing disorders and offers a better picture of how the mental illness affects Americans.

The study, published in the Archives of General Psychiatry, was based on analysis of data from face-to-face interviews with more than 43,000 adults as part of a 2001-2002 survey on alcohol and related conditions, including depression.

The results showed that 5.3 percent of U.S. adults experienced major depression in the 12 months preceding the survey and 13.2 percent had experienced major depression in their lifetime.

Help Yourself out of Depression

Who’s at Risk for Depression?

The highest lifetime risk of depression was among baby boomers aged 45 to 64, which researchers say is a shift from younger adults who were most at risk for depression in surveys conducted in the 1980s and 1990s.

The study showed that the risk of depression increases dramatically between ages 12 and 16, followed by a more gradual rise in risk until the early 40s when it begins to decline.

Researchers found about 60 percent of people with depression received treatment specifically for the disorder.

Other findings of the study include:

Of people with depression, nearly one-half said they wanted to die, one-third considered suicide, and about 9 percent attempted suicide. Among racial and ethnic groups, Native Americans had the highest prevalence of depression in their lifetime at 19 percent, followed by whites (15 percent), Hispanics (10 percent), blacks (9 percent), and Asian or Pacific Islanders (9 percent). Current and lifetime depression was also frequently associated with alcohol or drug use, smoking, and other mental disorders, such as personality and anxiety disorders.

Depression Takes its Toll on Relationships

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Hasin, D. Archives of General Psychiatry, October 2005; vol 62: pp 1097-1106. News release, National Institute on Alcohol Abuse and Alcoholism.