The avalanche of data pointing to the serious health risks associated with marijuana use continues to pour in, as the results of an expansive new study of almost half a million teenagers revealed that cannabis use causes significantly increased risk of severe mental disorders manifesting later in life, including bipolar and schizophrenia.

The study, published by JAMA Health Forum on February 20, analyzed data from the health records of over 460,000 teens in Northern California until they were 26 years old. Researchers found that the adolescents who reported using marijuana had twice the risk of “incident psychotic, bipolar, depressive, and anxiety disorders by age 26” compared to those who did not use the drug. In addition, the study found that teen users had significantly higher rates of depression and anxiety, with depression going up by a third and anxiety increasing by a quarter.

Dr. Ryan Sultan, a psychiatrist and cannabis researcher at Columbia University, described the results of the study as “very, very, very worrying.”

The new JAMA study is merely the latest datapoint in a body of evidence of marijuana’s health dangers stretching back at least a decade. After California legalized the recreational use of the drug in 2016, cases of cannabis-induced psychosis that required emergency room visits increased by 54% within three years. In 2019, the American Psychiatric Association found that there was a “strong association” between use of the drug and the “onset of psychiatric disorders.” In April 2022, a team of researchers found that if marijuana use were eradicated globally, it would result in a 10% reduction of all schizophrenia cases.

Other studies have laid out clear evidence showing the multi-faceted array of serious health risks associated with marijuana use. In July of last year, a major study that sifted through a cadre of 24 other studies found that regular cannabis use is associated with a twofold risk of serious cardiac problems, including death due to heart attacks. That study, along with another one from November 2023, found that regular marijuana use raises the risk of heart failure by 34% when compared to non-users. Dr. John Ryan, a cardiologist at the University of Utah Hospital, remarked that he has witnessed numerous “heart attacks in otherwise healthy people who use marijuana regularly.”

In addition, cases of severe vomiting associated with regular cannabis use (known as cannabinoid hyperemesis syndrome) are surging, with almost 2.8 million Americans now suffering from the illness. Substantial increases in suicidal thoughts are also strongly linked to the drug, with users considering suicide at a rate twice as high as non-users. Increases in other maladies associated with cannabis use include shorter life expectancy, bronchitis, emphysema, memory loss, and deficiencies in decision-making and verbal learning skills.

The public health crisis is emerging amid an explosion in marijuana use resulting from growing deregulation of the drug nationwide, with 24 states currently allowing recreational use. The number of regular marijuana users has tripled since 2012, with 18 million Americans now using the drug five times per week. In December, the Trump administration further deregulated cannabis, with President Trump signing an executive order directing federal agencies to reclassify marijuana from a Schedule I drug to a Schedule III drug, purportedly to expand research of the narcotic for potential medicinal uses.

But experts like Kevin Sabet, who serves as CEO of Smart Approaches to Marijuana, say that cannabis should be banned for the benefit of public health.

“A ban on these products is the only effective way to mitigate their harms,” he told The Washington Stand. “Studies like this JAMA report show that marijuana cannot be safely regulated, especially the hyper-potent version pushed by Big Weed today. This new study — which is only the latest in a long progression of work on the horrifying connection between marijuana and psychosis — undercuts the entire idea of a ‘safe’ and ‘regulated’ market. We were already supposed to have those, by the way; state-level legalizers promised precisely that.”

“The study highlights as well the fact that Big Weed is running the Big Tobacco playbook all over again (no shock given how tobacco is a major investor in the industry): hook them young and make customers for life,” Sabet added.