Researchers analyzed health administrative data of more than 12.23 million people from Ontario born between 1960 and 2009. They looked at diagnoses of schizophrenia spectrum disorder (SSD) and psychosis not otherwise specified (NOS), collectively referred to as psychotic disorders. The study assessed outcomes among these individuals over a 30-year period between 1993 and 2023.
Out of the 12.23 million people, 152,587, or 0.9 percent, were diagnosed with a psychotic disorder, the study said. The annual incidence of psychotic disorders was found to have increased by 60 percent among people aged 14 to 20 years between 1997 and 2023. Meanwhile, it was stable or even declined among those aged 21 to 50 years.
The incidence of schizophrenia was found to be 70 percent higher among individuals born in 2000-2004 compared to those born during 1975-79.
The percentage of people diagnosed with a psychotic disorder at 20 years of age was 104 percent higher among those born in 2000-2004, according to the study.
Among the 1975–1979 birth cohort, the mean age of diagnosis of psychotic disorders was 25.4 years, which declined to 23.2 years in the 1990-1994 cohort.
“Rates of substance use—including cannabis, stimulants, hallucinogens, and synthetic drugs—have increased over time in Canada; use of these substances is associated with the development and worsening of psychotic disorders,” the study noted.
The study cited other potential factors contributing to higher incidences of psychotic disorders among the younger groups, including the expansion of early psychosis intervention programs, socioeconomic stress, adverse childhood experiences, changes in maternal and neonatal health, and changing environmental exposure, such as urbanization.
A Feb. 2 CMAJ statement published on EurekAlert said recent studies from Australia and Denmark have also found schizophrenia diagnoses increasing among younger individuals over time, with the Ontario study contributing further evidence on this matter.
“We don’t yet know what’s driving these changes, and it’s likely there isn’t a single explanation. Understanding what’s behind this trend will be critical to prevention and early support,” Dr. Daniel Myran, one of the authors of the study, said.
“A leading possibility is substance use—including cannabis, stimulants, hallucinogens, and synthetic drugs. The use of substances, especially earlier in life, is associated with the development and worsening of psychotic disorders, and substance use in Canada has risen over the past two decades.”
The study was funded by Charite Universitatsmedizin Berlin, a leading university hospital in Germany; the University of Ottawa; North York General Hospital; and the Canada Research Chairs program, a grant by the Canadian government. Another researcher revealed competing interests, including receiving consulting fees and honoraria from several pharma companies such as AbbVie and Boehringer Ingelheim.
Situation in US
According to data from mental health care resource website Recovered, 40 U.S. states, three territories, and the District of Columbia allowed for the medical use of cannabis products as of June, with 24 states allowing nonmedical use.“I want to emphasize that the order I am about to sign is not the legalization, or it doesn’t legalize marijuana in any way, shape, or form, and in no way sanctions its use as a recreational drug,” Trump said. “It has nothing to do with it.”
