Suicide rates among youth are lowest in areas of the U.S. where prescriptions for a certain class of antidepressants are highest, researchers found after regulators warned of suicidal thoughts in young people on SSRIs.

The findings by Robert Gibbons, a professor of biostatistics and psychiatry at the University of Illinois at Chicago, are in Wednesday's issue of the American Journal of Psychiatry.

They come on the heels of warnings two years ago by Health Canada and other regulators, who urged doctors to keep an eye on patients taking selective serotonin reuptake inhibitors such as Prozac and Zoloft. 

Gibbons and his colleagues examined suicide rates of children ages five to 14 in each U.S. county from 1996 to 1998, including looking at SSRI prescription data.

"We found that counties with the highest prescription rates for SSRI drugs had the lowest suicide rates in children and adolescents," said Gibbons.

"This is just the opposite of what you would predict if SSRIs were producing suicide."

The effect was found after adjusting for sex, race, income, access to mental health care and variations in suicide rates.

The findings suggest the medication may make young people think about suicide, but they don't act on those thoughts.

"Studies to identify the best multi-step treatment sequences for individual patients and the development of more broadly effective treatments are needed," the team concluded.

Finding best drug takes time

A second study in the same issue of the journal suggests two-thirds of people with depression can be helped by medication, if they try several treatments.

Of the 123 study participants, 13 per cent had to take four different medications before they were helped, the researchers found.

But until patients were free of symptoms, they risked relapse.

"It's a sobering message when you get down to requiring three or four steps," said the chief researcher, Dr. John Rush of the University of Texas Southwestern Medical Center in Dallas. "It says that followup is critical" to make sure that people stay on the drugs, he said.

Results are hopeful

More than 3,600 adults diagnosed with major depression started the study by taking the SSRI Celexa, made by Forest Laboratories.

Since there was no comparison group of people not on a treatment, it is difficult to know how many people may have recovered over time or thanks to the drugs, said Dr. Thomas Insel, director of the U.S. National Institute of Mental Health.

"I think the overall results are hopeful," Insel said. "The problem with depression is that people and their families feel hopeless. The message here is that medication can be helpful."

The results of the second stage of the study looking at the effectiveness of counselling for depression will be published soon.

With files from the Associated Press