The Epidemiology of First-Episode Psychosis in Early Intervention in Psychosis Services: Findings From the Social Epidemiology of Psychoses in East Anglia [SEPEA] Study

Abstract

Objective: Few studies have characterized the epidemiology of first-episode psychoses in rural or urban settings since the introduction of early intervention psychosis services. To address this, the authors conducted a naturalistic cohort study in England, where such services are well established.

Method: All new first-episode psychosis cases, 16-35 years old, presenting to early intervention psychosis services in the East of England were identified during 2 million person-years follow-up. Presence of ICD-10 F10-33 psychotic disorder was confirmed using OPCRIT [operational criteria for psychotic illness]. Incidence rate ratios were estimated following multivariable Poisson regression, adjusting for age, sex, ethnicity, socioeconomic status, neighborhood-level deprivation, and population density.

Results: Of 1,005 referrals, 687 participants (68.4%) fulfilled epidemiological and diagnostic criteria for first-episode psychosis (34.0 new cases per 100,000 person-years; 95% CI=31.5-36.6). Median age at referral was similar for men (22.5 years; interquartile range: 19.5-26.7) and women (23.4 years; interquartile range: 19.5-29.1); incidence rates were highest for men and women before 20 years of age. Rates increased for ethnic minority groups (incidence rate ratio: 1.4; 95% CI=1.1-1.6), as well as with lower socioeconomic status (incidence rate ratio: 1.3; 95% CI=1.2-1.4) and in more urban (incidence rate ratio: 1.4;95%CI=1.0-1.8) and deprived (incidence rate ratio: 2.1; 95% CI=1.3-3.3) neighborhoods, after adjustment for confounders.

Conclusions: Pronounced variation in psychosis incidence, peaking before 20 years old, exists in populations served by early intervention psychosis services. Excess rates were restricted to urban and deprived communities, suggesting that a threshold of socioenvironmental adversity may be necessary to increase incidence. This robust epidemiology can inform service development in various settings about likely population-level need.

Keywords: Community Mental Health; Epidemiology; Psychosis; Schizophrenia.

Figure 1. Flow diagram of referrals to Early Intervention in Psychosis services

IR: Crude incidence rate per 100,000 person-years with 95% confidence intervals.

Figure 2. Age-sex specific incidence rates of selected psychotic disorders with 95% confidence intervals and cumulative percentage of cases presenting to Early Intervention Psychosis services

Crude incidence per 100,000 person-years and cumulative proportion of participants presenting to Early Intervention Psychosis services, by age and sex, with 95% confidence intervals (error bars) for (A) all clinically-relevant psychotic disorders, (B) non-affective psychotic disorders and (C) affective psychotic disorders. Likelihood ratio test [LRT] p-values for an age-sex interaction in Poisson regression models were (A) LRT-χ² on 6df=21.1: p<0.01, (B) LRT-χ² on 6df=15.4: p=0.02 and (C) LRT-χ² on 6df=9.5: p=0.15. All graphs are plotted on the same scale to show relative differences in crude incidence between disorders.