Transcript from CNN American Morning, Monday, October 25:

HEMMER: There is a fight brewing over the drug Accutane. Accutane is used to treat severe acne and the controversy here is triggered by new research that reveals how the drug may lead to depression in some patients. Dr. Sanjay Gupta has more this morning for us.

(BEGIN VIDEOTAPE)

REP. BART STUPAK (D) MICHIGAN: My oldest son B.J. -- Bart, Jr. -- died in May 14th, 2000. He shot himself.

DR. SANJAY GUPTA, CNN SR. MEDICAL CORRESPONDENT: Bart, Jr. was 17. Michigan Congressman Bart Stupak blames Accutane for his son's suicide, and he wants it off the market. But until now no one could say just how the drug might lead to depression.

STUPAK: This was the first study that really shows a biological link, physical evidence.

GUPTA: With this high-tech camera, psychiatrist Douglas Bremmer looked at the brains of 13 young adults taking Accutane for acne and another 15 on antibiotics. In the so-called Accutane brain, activity in this front part of the brain was down 21 percent.

DR. DOUGLAS BREMMER, EMORY UNIVERSITY: This plays a critical role emotion because there is a decrease in function in that part of the brain and it makes sense that there'd be changes in mood.

GUPTA: Accutane and generic versions already carry an imposing warning. Aside from cautions about birth defects, there is this: "Accutane may cause depression, psychosis, suicidal ideation, suicide attempts, and aggressive behavior." But that warning only started in 2002, four years after the Food and Drug Administration warned physicians that the drug might have psychiatric side effects. There are several lawsuits pending, including one by the family of 15-year-old patient Charles Bishop, who killed himself flying a small plane into a Tampa officer tower two years ago. Of course teens are more prone to clinical depression, and experts say the rate as measured by suicide and the number of teens seeking treatment is rising. A spokeswoman for Roche, the company that makes Accutane told us she doesn't know enough to comment on the new study but says that Roche has never found a link between its drug and suicide. Earlier this year, an FDA advisory panel recommended creating a formal registry of all patients on the drug to make it easier to keep track of side effects, but the agency has taken no action and the spokeswoman told CNN they are still deciding what to do. Roche says its open to a registry, but that could take a long time. Dr. Sanjay Gupta, CNN, Atlanta.

(END VIDEOTAPE) HEMMER: One other note on this story, Accutane is used by hundreds of thousands of people to fight severe acne.