WASHINGTON — Seven years ago, Mark Miller's 13-year-old son, Matt, who loved to ride bikes and play video games and excelled at making origami animals, hanged himself in his bedroom closet. His parents were devastated — and mystified.

"He had never threatened suicide," Miller recalled. "The only thing that had changed that week in his life was the medication."

Seven days before his death, Matt had begun taking Zoloft, a popular antidepressant prescribed by his doctor.

His father, struggling to understand what had happened, dived into the Internet, where he found books on the risks of antidepressants. He was soon convinced that the drug had caused Matt's death.

Miller helped start a website about the risks of the antidepressants. He wrote to the Food and Drug Administration and his congressman to enlist the government's help.

At first, no one took him seriously.

"I always felt people looked at me and said, 'That poor man, he's a bereaved father and he wants to blame it on the medication,' " Miller recalled.

But he gradually found other parents with stories like his. What began as a lonely mission grew into a crusade of about a dozen enraged parents motivated by the belief that their children were ripped from them by the drugs that were supposed to help them.

Finally, the government listened.

Last week, two FDA advisory panels recommended that the agency require companies to place prominent warnings — the kind boxed in dark lines — that there is a risk that antidepressants can cause suicidal behavior in children.

Doctors wrote an estimated 15 million prescriptions for nine antidepressants for children and teenagers last year.

Congressional committees are investigating whether the drugs are safe and whether the drug companies or the FDA improperly disguised or underestimated the drugs' risks to children. The FDA will also explore whether the drugs promote suicidal tendencies in adults and violent behavior in patients of all ages.

The FDA recently found that in clinical trials involving nine antidepressants taken by more than 4,000 children ages 6 to 18, hundreds experienced suicidal behavior or thoughts, although none killed themselves.

Miller said he and other parents like him had finally received "vindication and validation of what we've been saying for so long."

For years, as government agencies ignored his pleas, Miller was driven by guilt — he had told his son to take the pills — and sustained by his conversations with people seeking help because their loved ones had become suicidal or violent while taking antidepressants.

"I always thought if I could just reach one more person before his son or daughter did something tragic, it would be worth it. It has become a very bittersweet labor of love," Miller said.

Tom Woodward of suburban Philadelphia found Miller's website, but not until it was too late.

When Julie Woodward, 17, was going through a "rough patch" last year, a psychiatrist urged her to take Zoloft, which he assured the family was mild, safe and effective. Seven days later, her father found her body hanging in the garage.

The Woodwards' next-door neighbor, Doug Ross, a neuroscientist, turned to the Internet, where he learned that just a month earlier, the FDA had issued a warning that Paxil, another popular antidepressant, might be linked to increased risk of suicidal thoughts and attempts in young people.

It did not take long, Woodward recalled, before he and his wife were "absolutely convinced that the drug had done this," referring to Julie's death.

The Woodwards found Miller's website, http://www.drugawareness.org/ . They had long talks with Miller and other parents about the similar circumstances surrounding their children's deaths.

The families grew convinced that some drug companies had suppressed clinical trial data suggesting a link between the drugs and suicidal behavior. They resolved to make the government do something.

Today, they regularly share information about new scientific studies and plot strategies to push Congress to act.

"We've become very, very close to a lot of these other families," Tom Woodward said. "We are bound together by a parent's worst nightmare."

Most of the families met for the first time in person in February at a hotel bar in Bethesda, Md., where one FDA advisory panel was scheduled to hear their stories the next day.

Their accounts helped persuade the panels to urge the agency to warn doctors and families about the risk of suicide — and of the need to vigilantly monitor patients. But at that point, the FDA stopped short of suggesting that the drugs caused the suicidal behavior.

One of the most tireless members of the parents' group is Lisa Van Syckel of New Jersey, whose daughter, 15-year-old Michelle, was put on Paxil after having been misdiagnosed in 2000 as anorexic and depressed. It turned out that Michelle had Lyme disease.

But while on the antidepressant, Michelle, who had never attempted to harm herself or others, slammed her brother's head into a wall, went after another teenager with a baseball bat and attempted to take her own life. Van Syckel came across Miller's drug awareness website in 2002, as she was trying to ease her daughter off Paxil. Soon she was spending most of her time trying to get someone in power to warn other parents of the dangers of antidepressants. Most political leaders ignored her letters; one exception was Sen. Charles E. Schumer (D-N.Y.), who asked her to join him at a news conference in New York calling on the FDA to discourage the use of Paxil by children.

Then she turned to her own congressman, Rep. Michael Ferguson (R-N.J.). Ferguson became a major force behind a House subcommittee's investigation of the safety of the antidepressants and the role of drug companies and the FDA. "It was [Van Syckel] who really got my attention and prompted me to take an active and leading role," Ferguson said. It was not easy, he said, to get members of Congress to focus on the issue during an election year, when the country was already absorbed by terrorism and the war in Iraq.

But, he said, "we need to investigate this particular issue and get to the bottom of why this is having such an enormous impact on our kids. That cause has been moved forward light-years because of the powerful personal stories of people like Lisa Van Syckel."

Pressure from the families and members of Congress helped prod the FDA to have its advisory committees assess data from clinical trials of children on antidepressants.

Even the drug companies were impressed. "The families had an impact on helping this to move forward," said Dr. Joseph Camardo, medical director for Wyeth Pharmaceuticals North America, which makes one of the popular antidepressants. "I thought it was a great example of how the public can and should be heard."

The families were gratified when the advisory panels recommended last week that the FDA put emphatic warnings on the drugs. Mark Miller, who launched the crusade seven years earlier, called it "a wonderful first step." He added: "I didn't think it would happen in my lifetime."

The parents will continue to press the FDA to extend the warnings to adults and to add a warning that the drugs cause some people to become hostile or even homicidal. They also want Congress to hold the FDA and the drug companies accountable for failing to warn people sooner.

"I can't bear to think of the lives that have been lost in the intervening years," Miller said.