Over the past year, 16.5 million Americans age 18 or older - 1 in 13 adults - experienced at least one bout of major depression, according to a new government survey.

Less than two-thirds (64.5%) of those individuals got treated for their depression, the study found.

The report, from the Substance Abuse and Mental Health Services Administration (SAMHSA), drew on data from the agency's 2007 National Survey on Drug Use and Health, involving approximately 45,000 non-institutionalized adults. A major depressive episode was defined as any period of two weeks or longer characterized by depressed mood, loss of pleasure or interest, and at least four other symptoms, such as loss of appetite, lack of sleep and poor self-image.

Among other findings:

Rates of major depressive episodes were higher among people aged 18 to 25 (8.9%) or 26 to 49 (8.5%) compared to Americans aged 50 and older (5.8%). About 7.5% of all American adults suffered at least one depressive episode.
14.2% of Americans who described their health as "fair" or "poor" had a depressive episode, compared to 4.3% of those in self-described "excellent" health.
Among people who did seek out help for their depression, many (68.8%) saw or talked to a medical doctor or other health professional and got a prescription medication for their illness. A quarter (24%) saw a doctor but did not get this type of medication.
Among those with depression who did not receive treatment, more than 43% said cost was the reason they did not get help. About 29% said they could deal with their depression on their own, 18% said they didn't know where to turn for help, about 17% said they didn't have the time to seek care, 11.3% said their health insurance lacked the necessary coverage, and 11.1% cited concerns about confidentiality.

Whatever the reason, forgoing care is never a good idea, one expert said. "Depression is a medical condition that should be treated with the same urgency as any other medical condition," SAMHSA Acting Administrator Dr. Eric Broderick said in an agency news release.

-- E.J. Mundell

SOURCE: U.S. Substance Abuse and Mental Health Services Administration, news release, May 19, 2009