April 9 (HealthDay News) -- Nearly 30 percent of Americans need mental health care but only about a third of them receive it, researchers say.

Reporting in the March issue of the journal Psychiatric Services, researchers interviewed 816 people in Baltimore between 1993 and 1999.

They found that the most common conditions requiring treatment were alcohol dependence (14 percent) and major depression (11 percent). Other conditions looked at in the study were social phobia, panic disorder and agoraphobia.

"There are a number of people who need psychiatric care who aren't getting any," lead author Dr. Erick Messias, a psychiatrist at the Medical College of Georgia, in Augusta, said in a prepared statement. "There is a constellation of factors keeping people away from that care. This translates into people suffering for years, when there is a solution."

Reasons why people don't seek or get care include the belief that they'll get better on their own; the belief that treatment won't help; societal pressures and stigma; a lack of insurance coverage for mental health care; and too few mental health professionals.

It can be difficult for a person to determine whether they need to seek help for a mental health problem, but there are some key indicators, Messias said.

"I always ask patients how they sleep, because the way you sleep tells me a lot about how well you are. If you are so tired you are sleeping all the time or you can't sleep, that's a sign that something on your mind is not letting you relax," he said.

The state of a person's work and personal relationships are two other good indicators of mental health, Messias added.