Psychiatric Disorders Have Increased in More Recent Birth Cohorts, Study Suggests

Recent research uncovered that the incidence and cumulative proportion of patients diagnosed with psychotic disorders, such as schizophrenia, have increased in more recent birth cohorts and that the age of diagnosis has decreased in Ontario. The researchers, who published their work in the Canadian Medical Association Journal, said that further research is needed to identify potential contributors to the observed trends in their study.¹

The authors explained that previous reports suggested an incidence of psychotic disorders has either been stable or decreasing over time in high-income countries, but overall trends may not correctly capture birth cohort differences influenced by varying risk factor exposures. We sought to assess whether the incidence of psychotic disorders has changed across birth cohorts.¹

For this reason, they conducted a retrospective cohort study that used linked health administrative data on all people born between 1960 and 2009 in Ontario, Canada. Diagnoses of schizophrenia spectrum disorder (SSD) and psychosis not otherwise specified (NOS) between 1992 and 2023 were collected, and changes in incidence (diagnosis with no prior diagnosis in the previous 5 yr), cumulative incidence, and prevalence across birth cohorts were compared in 5-year increments. Additionally, the researchers utilized age–period–cohort (APC) models to compare birth cohort effects, accounting for differences in age and period when necessary.¹

Over 12 million people were enrolled, of whom 152,587 (0.9%) were diagnosed with a psychotic disorder during the study period. Between 1997 and 2023, the annual incidence of psychotic disorders increased by approximately 60% among individuals aged 14 to 20 years and was stable or declined among those aged 21 to 50 years. Additionally, the investigators observed birth cohort increases in the incidence of psychotic disorders and decreases in the age of diagnosis.¹

The APC models indicated that the incidence of schizophrenia was approximately 70% (incidence rate ratio [IRR], 1.70; 95% confidence interval [CI], 1.63–1.78) higher among those born in 2000 to 2004 compared with those born in 1975 to 1979, with increases in psychosis NOS (IRR, 2.89; 95% CI, 2.73–3.06) across birth cohorts being greater than those in SSD (IRR, 1.32; 95% CI, 1.25–1.40). Compared with those born in 1975 to 1979, the percentage of people who had been diagnosed with a psychotic disorder at 20 years of age was around 104% higher (0.55% vs 0.27%) for those born in 2000 to 2004 and 37.5% higher (1.32% vs 0.96%) at 30 years for those born in 1990 to 1994. Further, the authors observed that birth cohort effects were comparable among males and females, and these were consistent in sensitivity analyses examining diagnoses in outpatient settings only or in hospital settings only.¹

“Individuals with psychotic disorders face substantial morbidity and risk of premature death, and often require substantial health services and social support,” Daniel Myran, MD, MPH, CCFP, FRCPC, Gordon F. Cheesbrough Research Chair in Family and Community Medicine, North York General, and a scientist at ICES and the Bruyère Health Research Institute, said in a news release. “Consequently, the observed trends raise important questions about possible causes and consequences of increasing numbers of psychotic disorder diagnoses.”²

Regarding limitations, the investigators acknowledged that their findings are possibly subject to APC confounding, and disengaging the influence of these separate effects is challenging. Additionally, they noted being unable to observe more recent birth cohorts at older ages, and the observed trends may not persist long term. The authors wrote that underestimation in earlier cohorts may be possible due to participants born in the 1960s and early 1970s entering observation once they reach their twenties or thirties; however, consistent increases remained evident even when comparing cohorts fully observable from adolescence (eg, higher incidence among those born in the 1990s vs those born in the 1980s).¹

Further, the changes observed during the study may partially reflect increased awareness and reduced stigma regarding mental health, leading to more help-seeking behavior, especially for milder symptoms. However, psychotic disorders—which present with substantial acuity and impairment—would be much less susceptible to such biases, explained the authors.¹

“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,” Myran explained. “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 2 decades.”²

REFERENCES

1. Myran DT, Gibb M, Pugliese M, et al. Incidence of psychotic disorders by birth cohort: a population-based cohort study in Ontario, Canada. CMAJ. 2026;198(4):E118-E127. doi:10.1503/cmaj.250926

2. Canadian Medical Association Journal. Psychosis rates increasing in more recent generations. News release. February 2, 2026. Accessed February 5, 2026. https://www.eurekalert.org/news-releases/1114423