Teenagers and young adults in the United States are at risk of developing a psychotic disorder or schizophrenia after using cannabis, say doctors, researchers and a government agency, as thousands of cases among teenagers have been diagnosed.

The number of people diagnosed with a mental health or psychotic disorder after smoking cannabis was 50 percent higher in November than it was four years ago, Truveta, a healthcare analytics company, said.

However, the drug remains popular nationwide, with about 52 million people admitting using it at some time in 2021, federal data showed.

Figures from the National Institute on Drug Abuse in 2021 showed that an estimated 30 percent of high school seniors said they had used marijuana in the past year.

The stigma associated with pot, a nickname for marijuana, has significantly diminished, and while it is still illegal federally, it has been legalized for recreational use in 24 states and for medical use in 38.

"Cannabis is one environmental factor that confers risk for schizophrenia," Deepak D'Souza, an Albert E. Kent Endowed Professor of Psychiatry of the School of Medicine at Yale University and director of the Schizophrenia Neuropharmacology Research Group at Yale, told China Daily.

"It's likely that some complex interactions between cannabis exposure and other factors such as genetic risk for schizophrenia contribute to the risk.

"A very high proportion of individuals who experience substance-induced psychosis will later go on to develop schizophrenia. This is particularly so for cannabis-induced psychosis."

The US Centers for Disease Control and Prevention warned that people who use marijuana "are more likely to develop temporary psychosis, not knowing what is real, hallucinations, and paranoia and long-lasting mental disorders, including schizophrenia, a type of mental illness where people might see or hear things that are not really there".

High risk

If someone had just one psychotic episode after using cannabis, there was a 47 percent risk of them developing schizophrenia or bipolar disorder, according to a 2017 study published in the American Journal of Psychiatry. Those aged 16 to 25 faced the highest risk.

Fears over an uptick in cannabis-induced disorders developed after the COVID-19 pandemic left many — especially children and teenagers — suffering from strained mental health, anxiety and addiction.

"The pandemic lent (itself) to triggering substance abuse," Karen Cassiday, a clinical psychologist and managing director of the Anxiety Treatment Center of Greater Chicago, told China Daily.

Anxious teens use pot, hoping it will calm their nerves. But one of the adverse effects is that it can spike anxiety and paranoia.

In Colorado, following the legalization of recreational cannabis from 2012 to 2014, there was a ninefold increase in the number of emergency department visits for psychotic disorders from cannabis use, according to a study by epidemiologist and biostatistician Katelyn Hall and others.