U.S. Surgeon General Jerome Adams called the spread of state marijuana legalization "a massive public health experiment on our citizenry."
Appearing before a hearing of the Senate Caucus on International Narcotics Control on Wednesday, Adams emphasized that legalization has proceeded without adequate scientific evidence. He said state lawmakers have rushed to enter the lucrative drug market despite the fact that many people do not fully understand the risks associated with marijuana use. He highlighted the risks of marijuana use by teenagers, pregnant women, and recent mothers—all of which, he said, remain chronically under-discussed in spite of their support in the scientific literature.
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"No amount of marijuana use during pregnancy or adolescence is known to be safe," Adams said. "Therefore communities must consider and should not minimize the short and long-term public health impacts of marijuana use."
Adams pointed to research showing that chronic adolescent marijuana use is associated with depressed IQ, as well as changes in areas of the brain associated with attention, memory, decision-making, and motivation—changes which do not abate even after a month of abstinence. He also noted that scientific evidence suggests that marijuana use by pregnant women is a major risk factor for pre-term birth, which is in turn linked to a host of future health problems.
Adams's concerns were echoed by fellow panelist Dr. Nora Volkow, who has led the National Institute on Drug Abuse (NIDA) since 2003. She said the endocannabinoid system, which marijuana stimulates, "plays a critical role in helping to orchestrate brain development." Volkow, who is known for her pioneering research using MRI technology to study drug use and addiction, said drug use hinders this brain development.
"Exposure to marijuana during early development can impact the function of the brain later in life," she said.
Adams and Volkow both expressed concerns that the wave of marijuana legalization sweeping the United States is proceeding without an adequate public understanding of these risk factors, or adequate scientific understanding of marijuana in general.
A recent study from Denver Health, for example, found that 70 percent of dispensaries would recommend that pregnant women use marijuana to control morning sickness, in spite of the known risks to fetal health. And, according to Adams, only a third of adolescents said they believe weekly marijuana use is harmful, in spite of the evidence of its effects on the developing brain.
Sen. John Cornyn (R., Texas) drew an analogy between marijuana's rapid spread and the rise of cigarettes, which also became massively popular before comprehensive studies of their long-term risks had been conducted.
"As the surgeon general, I want every policy decision to be infused with as much science as possible, and you are correct, we've seen this play before," Adams said. "We've seen it with a number of substances," including cocaine, opioids, and cigarettes.
Both Adams and Volkow emphasized the need for substantially more research, especially in light of the changing shape of marijuana consumption. In particular, rising THC concentrations and proliferating varieties have left organizations like NIDA struggling to keep up. Volkow noted that "with the use of marijuana at very high content…we are finding negative medical effects that we did not know existed." She pointed to the rise of hyperemesis: THC-induced continual vomiting that was not discovered until 2006.
"We don't know what we don't know," Adams said. "So we don't want to conduct this experiment on our citizenry, and that's adults and young people."
The hearing was headed by Sen. Dianne Feinstein (D., Calif.) and Cornyn, likely in line with the latter's stated desire for hearings on marijuana's legal status before proceeding with other federal marijuana-related legislation.
Loosening marijuana laws remains popular among the public. On Wednesday, Gallup announced that public support for legalizing marijuana remained steady in 2019, with two-thirds of Americans in favor. Legalization is a key feature of almost every 2020 Democrat's platform, in spite of the concerns raised by Adams, Volkow, and others.