The United States Surgeon General, Dr. Vivek Murthy, announced on Monday that he would push for a warning label on social media platforms advising parents that using the platforms might damage adolescents’ mental health.

Warning labels — like those that appear on tobacco and alcohol products — are one of the most powerful tools available to the nation’s top health official, but Dr. Murthy cannot unilaterally require them; the action requires approval by Congress. No such legislation has yet been introduced in either chamber.

A warning label would send a powerful message to parents “that social media has not been proved safe,” Dr. Murthy wrote in an essay published in The New York Times opinion section on Monday.

In his essay, he cast the effects of social media on children and teenagers as a public health risk on par with road fatalities or contaminated food.

“Why is it that we have failed to respond to the harms of social media when they are no less urgent or widespread than those posed by unsafe cars, planes or food?” Dr. Murthy wrote. “These harms are not a failure of willpower and parenting; they are the consequence of unleashing powerful technology without adequate safety measures, transparency or accountability.”

Dr. Murthy pointed to research that showed that teens who spent more than three hours a day on social media faced a significantly higher risk of mental health problems, and that 46 percent of adolescents said social media made them feel worse about their bodies.

U.S. teens are spending an average of 4.8 hours per day on social media platforms like YouTube, TikTok and Instagram, according to a Gallup survey of more than 1,500 adolescents released last fall.

In an interview last month, Dr. Murthy said he had repeatedly heard from young people who “can’t get off the platforms,” often finding that hours had passed when they had intended to just check their feeds.

“The platforms are designed to maximize how much time we all spend on them,” he said. “It’s one thing to do that to an adult, and another thing to do it to a child, whose impulse control is still developing, whose brain is at a sensitive phase of development.”

Past warning labels have had significant effects on behavior. In 1965, after a landmark report from the Surgeon General, Congress voted to require all cigarette packages distributed in the United States to carry a warning that using the product “may be hazardous to your health.”

That was the beginning of a 50-year decline in smoking. When the warning labels appeared, around 42 percent of U.S. adults were daily cigarette smokers; by 2021, that portion had dropped to 11.5 percent.

There is fierce debate among researchers about whether social media is behind the crisis in child and adolescent mental health. In his new book, “The Anxious Generation,” the social psychologist Jonathan Haidt points to the 2007 release of the Apple iPhone as an inflection point, setting off a sharp increase in suicidal behavior and reports of despair.

Other experts say that, while the rise of social media has coincided with declines in well-being, there is no evidence that one caused the other, and point instead to factors like economic hardship, social isolation, racism, school shootings and the opioid crisis.

Dr. Murthy has long indicated that he views social media as a health risk. In May 2023, he issued an advisory on the subject, warning that “there are ample indicators that social media can also have a profound risk of harm to the mental health and well-being of children and adolescents.”

In that statement, Dr. Murthy acknowledged that the effects of social media on adolescent mental health were not fully understood. Research suggests the platforms offer both risks and benefits, providing community for young people who might otherwise feel marginalized.

Still, it urged parents to begin setting limits on their children’s social media use immediately, and to keep mealtimes device-free.

With his call for a warning label, Dr. Murthy is further dialing up the tone of urgency.

“One of the most important lessons I learned in medical school was that in an emergency, you don’t have the luxury to wait for perfect information,” he wrote. “You assess the available facts, you use your best judgment, and you act quickly.”

Recalling the words of a tearful mother whose child had died of suicide after being bullied online, he compared the current moment with landmark public health campaigns of the past.

“There is no seatbelt for parents to click, no helmet to snap in place, no assurance that trusted experts have investigated and ensured that these platforms are safe for kids,” he wrote. “There are just parents and their children, trying to figure it out on their own, pitted against some of the best product engineers and most well-resourced companies in the world.”