Younger people are being diagnosed with psychotic disorders at higher rates and at younger ages than those born earlier, a large study has found, leaving experts uncertain about what’s driving the rise.
The study of more than 12 million people, conducted by a team of researchers in Canada, included 12.2 million people born in Ontario between 1960 and 2009, of whom 152,587 were diagnosed with a psychotic disorder, such as schizophrenia.
“Individuals with psychotic disorders face substantial morbidity and risk of premature death, and often require substantial health services and social support,” said co-author of the research, Dr Daniel Myran, of Canada’s North York General Hospital.
He said the surge in cases raises “important questions about possible causes and consequences”, but also said there was no clear evidence for what was driving the increases.
However, the research team suggested a range of different factors including older parental age, increased socioeconomic and migration‑related stress, as well as “some negative childhood experiences” among younger generations. Substance use may also be playing a role.
“We still don’t know what’s driving these changes, and it’s unlikely there’s a single cause. Understanding the forces behind this trend will be crucial for prevention and early intervention,” said Dr Myran.
“One leading possibility is substance use – from cannabis and stimulants to hallucinogens and synthetic drugs. Using these substances, particularly early in life, is linked to the onset and worsening of psychotic disorders, and substance use in Canada has climbed over the past two decades.”
The research revealed that among people aged 14 to 20 years, rates of new cases increased by 60 per cent between 1997 and 2023.
The team said the increases in psychotic disorders occurred in more recent birth cohorts, with rates of new cases beginning to increase for those born in the 1980s and later.
People born between 2000 and 2004 were estimated to have a 70 per cent greater rate of new diagnoses of psychotic disorders compared with those born between 1975 and 1979.
Overall, the total number of people diagnosed with a psychotic disorder by the time they were 30 years old rose by 37.5 per cent for those born in 1990 to 1994 compared with those born in 1975 to 1979.
While broader research on generational shifts in psychotic disorders remains sparse, the team highlighted recent studies from Denmark and Australia which also reported rising rates of schizophrenia among younger people. The new findings add further weight to concerns that these patterns are emerging across multiple countries.
The authors said more research is needed to uncover what’s driving the rise in psychosis and why the risks appear to differ between generations.
The research is published in the Canadian Medical Association Journal.
