Secular trends in the prevalence of schizophrenia among different age, period and cohort groups between 1990 and 2019

Background: Schizophrenia remains a major public health challenge, and designing efforts to manage it requires understanding its prevalence over time at different geographic scales and population groups.

Methods: Drawing on data from the Global Burden of Disease study 2019, annual percentage change of schizophrenia was assessed across different age, period and cohort groups at different geographic scales from 1990 to 2019. We examined associations of prevalence with the sociodemographic index.

Results: Global prevalence of schizophrenia in 2019 was 23.60 million (95 % uncertainty interval: 20.23-27.15), with China, India, the USA and Indonesia accounting for 50.72 % of it. Global prevalence increased slightly from 1990 to 2019, with an annual percentage change of 0.03 % (95 % confidence interval 0.01-0.05). Regions with intermediate sociodemographic index accounted for greater proportion of prevalence increasing than regions with high index. Prevalence decreased among those born after 1979 in regions with intermediate sociodemographic index, whereas it consistently improved among all birth cohorts in regions with low index. Regardless of sociodemographic index, prevalence was highest among individuals 30-59 years old than younger or older groups.

Conclusions: Prevalence of schizophrenia has shown small increases globally over the last three decades. The burden of disease is heavier in relatively less affluent regions, and it disproportionately affects individuals 30-59 years in all regions. Meanwhile, for regions with lower sociodemographic indices, the recent increasing burden among birth cohorts is more pronounced. These findings may help guide futural design of measures to manage or prevent schizophrenia in communities at higher risk.