Temporal variation in the incidence of treated psychotic disorders in young people

Abstract Introduction The incidence of psychotic disorders varies between geographical areas, however less is known about whether it varies over time in the same region. Analyzing this temporal variation of incidence could improve the allocation of healthcare resources and our understanding of the aetiology of psychotic disorders. This study aimed to determine whether there was a change in the incidence of psychotic disorders over a six-year period. Methods Young people aged 15 to 24 presenting with a first episode of psychosis (FEP) attending an early intervention service in Melbourne between 2011 and 2016 were included. The population at-risk was determined from the two corresponding census periods and analyses were adjusted for age, sex and migrant status. Results A total of 1217 young people presented with a FEP over the six-year period and the crude incidence rate in 2011 was 102.4 per 100,000 population at-risk, compared to 125.4 in 2016. There was an increase in the incidence by 33% in 2015 (aIRR = 1.33, 95% CI 1.09–1.63) and 28% in 2016 (aIRR = 1.28, 95% CI 1.05–1.56). When examined according to diagnostic groups, there was an increase in the incidence of substance-induced psychotic disorders among females in 2015 (aIRR = 4.62, 95% CI 1.02–20.8). Discussion This study shows significant temporal variations in the incidence of treated psychotic disorders. These findings demonstrate that early intervention services should continually monitor incidence case numbers and funding should be provided accordingly, to ensure the required intensive and comprehensive treatments can be sustained.