Experts Warn of Marijuana’s Long-Term Damage to Brain and Developing Fetuses Amid Push for Reclassification

Reclassification of marijuana sparks heated debate as experts highlight risks of brain damage and impact on developing fetuses

  • Staff Consortium
  • May 22, 2024

The Biden administration's recent move to reclassify marijuana as a Schedule III drug, placing it on par with anabolic steroids and Tylenol with codeine, has sparked a significant debate. While proponents argue that this reclassification would provide tax benefits and boost the cannabis industry, experts warn of the substantial negative health impacts associated with marijuana use.

Rising Marijuana Use and Legalization Trends

According to the Wall Street Journal, a 2022 survey sponsored by the National Institutes of Health found that 28.8% of Americans aged 19 to 30 had used marijuana in the preceding 30 days, more than three times the number who smoked cigarettes. Among those aged 35 to 50, 17.3% had used marijuana, compared to 12.2% who smoked cigarettes. Despite its federal status as an illegal substance, marijuana is now legal for recreational use in 24 states and for medical purposes in another 14 states.

Health Risks and Addiction

Bertha Madras, a psychobiology professor at Harvard Medical School and a renowned expert on marijuana, vehemently opposes the reclassification. In a recent opinion on WSJ, she said, "It’s a political decision, not a scientific one. And it’s a tragic one." Ms. Madras has dedicated 60 years to studying psychoactive drugs and has extensively reviewed the impacts of marijuana.

She explains that the addiction potential of marijuana is as high or higher than some other drugs, particularly for young people. Approximately 30% of cannabis users develop some degree of use disorder, compared to 13.5% of alcohol drinkers. "Most people who use marijuana are using it to become intoxicated and to get high," Madras notes. She also points out that academic outcomes and college completion rates are significantly worse for marijuana users compared to those who drink alcohol.

Cognitive Impairment and Driving Risks

One of the critical issues with marijuana use is its impact on cognitive function and driving safety. Unlike alcohol, there are no established medical "cutoff points" to determine whether it’s safe to drive after using marijuana. States where marijuana is legal have reported increases in car accidents. "Marijuana just sits there and promotes brain adaptation," says Ms. Madras, explaining that the substance remains in the brain much longer than alcohol.

High-Potency Marijuana and Mental Health

Today's cannabis is far more potent than it was 30 years ago, with significantly higher levels of THC, the main psychoactive ingredient. This increased potency heightens the risks associated with marijuana use, including anxiety, depression, impaired memory, and cannabis hyperemesis syndrome—a condition involving severe vomiting due to long-term use.

Ms. Madras highlights mounting evidence that cannabis can cause schizophrenia. A study of 6.9 million Danes suggested that up to 30% of young men’s schizophrenia diagnoses could have been prevented if they had not become dependent on marijuana. She emphasizes that users of other potent recreational drugs develop chronic psychosis at much lower rates compared to marijuana users.

Impact on Pregnant Women and Children

The rise in marijuana use among pregnant women is another significant concern. Marijuana use during pregnancy has been linked to increased preterm deliveries, admissions of newborns into neonatal intensive care units, lower birth weights, and smaller head circumferences. THC, the active ingredient in cannabis, crosses the placenta and affects brain development in fetuses. Adolescents exposed to THC in utero show increased aggressive behavior, cognitive dysfunction, and symptoms of ADHD and OCD.

Lack of Medicinal Benefits

Despite widespread claims of marijuana's medicinal benefits, Ms. Madras found strong evidence only for neuropathic pain. For other types of pain and conditions, there is no robust evidence from high-quality trials to support its use. She compares the current marketing of marijuana to that of opioids, where benefits are exaggerated and risks minimized.

The Call for Rigorous Research

Ms. Madras criticizes the argument that cannabis cannot be properly studied unless it is removed from Schedule I. She has successfully studied THC despite the additional paperwork required. She urges wealthy donors and advocates to fund rigorous clinical trials instead of ballot initiatives.


Reclassifying marijuana would not legalize recreational use under federal law but would allow businesses to deduct expenses and send a cultural signal that marijuana use is normal. Ms. Madras warns that this sets a dangerous precedent and contradicts efforts to prevent addiction. "This is not a war on drugs," she says. "It’s a defense of the human brain at every possible age from in utero to old age."

The debate over marijuana reclassification underscores the need to balance potential benefits with the substantial health risks highlighted by experts like Ms. Madras. 

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