(CNN) - US Surgeon General Dr. Jerome Adams has a warning for pregnant women and teens when it comes to weed.
"No amount of marijuana use during pregnancy or adolescence is safe," Adams said during a press conference Thursday in Washington to announce an advisory on the risks of marijuana use among adolescents and pregnant women.
Adams sounded the alarm about increasing marijuana use among those groups in recent years.
"In pregnant women, marijuana is now actually the most commonly used illicit drug," he said. "Marijuana is now the third most commonly used illicit substance in adolescents behind alcohol and e-cigarettes."
President Donald Trump recently donated his second quarter salary to promote the surgeon general's latest advisory, US Health and Human Services Secretary Alex Azar said during the press conference. That amounts to $100,000, and it will be spent on a public awareness campaign.
"This advisory makes clear that marijuana poses substantial risks to the developing brain," Azar said.
"For many it can be addictive and it's especially dangerous for adolescents and pregnant women because of what we know about how it affects the developing brain," he said. "We need to be clear: Some states' laws on marijuana may have changed but the science has not and federal law has not."
Marijuana is now legal either recreationally or medically across 33 states.
The surgeon general warned that marijuana use during pregnancy can be dangerous to a developing fetus, and that marijuana use during adolescence is associated with changes in areas of the brain involved in attention, memory, decision-making and motivation.
This is Adams' first advisory this year and his third since being named surgeon general in 2017. Last year, he issued an advisory on using the medication naloxone to reverse an opioid overdose, and an advisory on e-cigarette use among youth, calling it an "epidemic."
The advisory is also the first on marijuana since one issued by Surgeon General C. Everett Koop in 1982, Azar said. Adams mentioned in his announcement that marijuana has changed since then.
"This ain't your mother's marijuana," Adams said.
"Not enough people know that today's marijuana is far more potent than in days' past. The amount of THC -- the component responsible for euphoria and intoxication but also most of marijuana's documented harms -- has increased three- to five-fold over the last few decades," he said. "We've seen an increase in emergency department visits for psychosis, overdose and accidental ingestions. And nearly one in five people who begin marijuana use during adolescence become addicted."
The American Medical Association applauded the surgeon general's advisory.
"We strongly support this effort as the AMA has long discouraged cannabis use by youth, pregnant women, and women who are breastfeeding and has called for research to determine the consequences of long-term cannabis use in these populations," Dr. Patrice Harris, president of the AMA, said in a written statement on Thursday.
"The AMA believes that scientifically valid and well-controlled clinical trials conducted under federal investigational new drug applications are necessary to assess the safety and effectiveness of all new drugs, including potential cannabis and cannabinoid products for medical use," she said in part. "Due to legal and regulatory barriers to cannabis and cannabinoid research, physicians and patients do not currently have the evidence needed to understand the health effects of these products and make sound clinical decisions regarding their use."
There has been an increase in the percentage of women in the United States who are using marijuana during pregnancy. That percentage rose overall from 3.4% of pregnant women in 2002 to 7% in 2017, according to a study published in the medical journal JAMA in June.
Nationally, about 38% of high school students report having used marijuana in their life, according to the US Centers for Disease Control and Prevention.
CNN's Casey Riddle contributed to this report.
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