July 30 (HealthDay News) -- New research from the National Institute of Mental Health gives 15 million people suffering with depression hope for a future faster-acting antidepressant.

The medication ketamine begins to take effect on the brain cells involved in depression within hours, researchers report.

"Our research is showing us how to develop medications that get at the biological roots of depression. This new finding is a major step toward learning how to improve treatment for the millions of Americans with this debilitating disorder; toward eliminating the weeks of suffering and uncertainty they have to endure while they wait for their medications to work," Dr. Elias Zerhouni, director of the National Institutes of Health, said in a prepared statement.

SEATTLE— When people receive brief telephone-based psychotherapy soon after starting on antidepressant medication, strong positive effects may continue 18 months after their first session. So concludes a Group Health study in the April Journal of Consulting and Clinical Psychology.

This paper describes one more year of follow-up since a 2004 Journal of the American Medical Association (JAMA) report on the same random sample of Group Health patients.

“With close to 400 patients, this is the largest study yet of psychotherapy delivered over the telephone,” said Evette J. Ludman, PhD, senior research associate, Group Health Center for Health Studies, the paper’s lead author. “It’s also the first to study the effectiveness of combining phone-based therapy with antidepressant drug treatment as provided in everyday medical practice.”