A significant population-based cohort study published in the Canadian Medical Association Journal reveals an increasing incidence of psychotic disorders, such as schizophrenia, among younger birth cohorts in Ontario. Researchers examined data for over 12.2 million individuals born between 1960 and 2009, identifying 152,587 diagnoses of psychotic disorders across the study period.
Specifically, the rates of new cases among individuals aged 14 to 20 years escalated by 60% between 1997 and 2023, according to the analysis conducted by institutions including ICES and the Bruyère Health Research Institute. The increase began manifesting in cohorts born in the 1980s, with those born between 2000 and 2004 showing an estimated 70% higher rate of new diagnoses compared to those born in the late 1970s.
Dr. Daniel Myran, a lead author and scientist at ICES, noted that these rising trends raise critical questions regarding the causes and subsequent demands placed on health services and social support systems. The total cumulative number of individuals diagnosed with a psychotic disorder by age 30 increased by 37.5% for the 1990 to 1994 birth cohort relative to the 1975 to 1979 cohort.
While the increases were consistent across both sexes, males continued to carry a higher overall risk throughout the study duration. Those diagnosed with nonaffective psychoses, like schizophrenia, frequently resided in low-income neighborhoods and had prior mental health or substance use treatment records.
Researchers suggest several potential contributing factors that have changed across recent birth cohorts, including increased parental age, socioeconomic stress, migration-related pressures, and negative childhood experiences. However, the authors place particular emphasis on the documented rise in substance use in Canada over the last two decades.
Substance use, including stimulants and cannabis, is cited as a leading possibility, as early-life exposure is strongly associated with the onset and exacerbation of psychotic conditions. The authors stress that understanding the precise drivers behind these trends is essential for developing targeted prevention and early intervention strategies.
This Canadian evidence aligns with recent findings from studies in Denmark and Australia, which also documented temporal increases in schizophrenia diagnoses among younger populations. Further epidemiological research is required to isolate the specific variables responsible for these concerning cohort-specific shifts in mental health incidence.
