The Trump administration on Thursday warned adolescents and pregnant women against using marijuana, calling it "a dangerous drug."
"While the perceived harm of marijuana is decreasing, the scary truth is that the actual potential for harm is increasing," U.S. Surgeon General Jerome Adams said.
Adams and Health and Human Services Secretary Alex Azar said the concentration of THC — the chemical in marijuana that gives users a high — is three times higher now than it was in the 1990s and early 2000s.
"This ain't your mother's marijuana," Adams said. "The higher the THC delivery, the higher the risk."
Adams said marijuana has been scientifically shown to be harmful to the developing brains of teenagers and to the human fetus. He said frequent use of marijuana by teenagers can affect still-developing brains, especially the parts associated with attention, memory and decision-making.
The American College of Obstetricians and Gynecologists and the American Academy of Pediatrics have said women should not use marijuana during pregnancy to avoid harming their fetuses and should stop using the drug if they find out they are pregnant.
Brett Giroir, an assistant secretary of health and human services, has said pregnant women who use marijuana to combat morning sickness should quit.
Azar said President Donald Trump was donating $100,000 to help fund a digital campaign to highlight the risks of marijuana.
Marijuana is still illegal on a federal level, but several states have legalized limited amounts for recreational or medical uses.