Lilly also acknowledged Wednesday that four other suicides have occurred during several years of human testing of duloxetine, the main ingredient in drugs Lilly is developing to treat depression and stress urinary incontinence.

Other antidepressants have recently been scrutinized for possible links to suicide in young people. Earlier this month, a government drug advisory panel said it wasn't clear that some of these drugs lead to suicide, but until that is settled, parents and doctors need better warnings that they may cause agitation, anxiety and hostility in a few young patients.

In the duloxetine test, a 19-year-old former college student hanged herself Saturday in a Lilly research lab at the Indiana University Medical School. She had recently been weaned from a higher-than-normal dose of the drug, a spokesman for Eli Lilly told The Indianapolis Star.

"It's a sad fact, it's a tragic fact, that sometimes these patients commit suicide," Lilly spokesman Rob Smith said. But the company does not believe duloxetine played a part in the death of Traci Johnson of Bensalem, Pa., who was described as healthy and not suffering from depression.

The other suicides involved patients with depression. Some activists who question the safety of antidepressants said Johnson's death points to the drug as a possible cause.

Three participants in the study in Indianapolis and 16 volunteers in Evansville have quit. The study still has about 100 participants, Smith said

"We clearly anticipated that a number of patients would not continue the study," Smith said, adding that the Indianapolis-based company would still have enough participants to complete the study.

The rate of suicide for depressed patients taking duloxetine is lower than for those taking a placebo, Smith said. It also is lower than the rate for another group of antidepressants known as SSRIs, or selective serotonin reuptake inhibitors. Drugs such as Prozac, Paxil and Zoloft are SSRIs.