Abstract
BackgroundWe conducted a systematic review of incidence rates in England over a sixty-year period to determine the extent to which rates varied along accepted (age, sex) and less-accepted epidemiological gradients (ethnicity, migration and place of birth and upbringing, time).ObjectivesTo determine variation in incidence of several psychotic disorders as above.Data SourcesPublished and grey literature searches (MEDLINE, PSycINFO, EMBASE, CINAHL, ASSIA, HMIC), and identification of unpublished data through bibliographic searches and author communication.Study Eligibility CriteriaPublished 1950–2009; conducted wholly or partially in England; original data on incidence of non-organic adult-onset psychosis or one or more factor(s) pertaining to incidence.ParticipantsPeople, 16–64 years, with first -onset psychosis, including non-affective psychoses, schizophrenia, bipolar disorder, psychotic depression and substance-induced psychosis.Study Appraisal and Synthesis MethodsTitle, abstract and full-text review by two independent raters to identify suitable citations. Data were extracted to a standardized extraction form. Descriptive appraisals of variation in rates, including tables and forest plots, and where suitable, random-effects meta-analyses and meta-regressions to test specific hypotheses; rate heterogeneity was assessed by the I2-statistic.Results83 citations met inclusion. Pooled incidence of all psychoses (N = 9) was 31.7 per 100,000 person-years (95%CI: 24.6–40.9), 23.2 (95%CI: 18.3–29.5) for non-affective psychoses (N = 8), 15.2 (95%CI: 11.9–19.5) for schizophrenia (N = 15) and 12.4 (95%CI: 9.0–17.1) for affective psychoses (N = 7). This masked rate heterogeneity (I2: 0.54–0.97), possibly explained by socio-environmental factors; our review confirmed (via meta-regression) the typical age-sex interaction in psychosis risk, including secondary peak onset in women after 45 years. Rates of most disorders were elevated in several ethnic minority groups compared with the white (British) population. For example, for schizophrenia: black Caribbean (pooled RR: 5.6; 95%CI: 3.4–9.2; N = 5), black African (pooled RR: 4.7; 95%CI: 3.3–6.8; N = 5) and South Asian groups in England (pooled RR: 2.4; 95%CI: 1.3–4.5; N = 3). We found no evidence to support an overall change in the incidence of psychotic disorder over time, though diagnostic shifts (away from schizophrenia) were reported.LimitationsIncidence studies were predominantly cross-sectional, limiting causal inference. Heterogeneity, while evidencing important variation, suggested pooled estimates require interpretation alongside our descriptive systematic results.Conclusions and Implications of Key FindingsIncidence of psychotic disorders varied markedly by age, sex, place and migration status/ethnicity. Stable incidence over time, together with a robust socio-environmental epidemiology, provides a platform for developing prediction models for health service planning.
Highlights
Schizophrenia and other psychotic disorders exhibit variation in incidence [1,2], prevalence [3] and course [4] along a number of dimensions, providing important signposts for clinical care, health service planning, etiological research and public health [5]
We found no evidence to support an overall change in the incidence of psychotic disorder over time, though diagnostic shifts were reported
Incidence rates were generally highest for all syndromes, followed by non-affective psychoses, of which schizophrenia was a subset, with the incidence of affective psychoses, including bipolar disorder and psychotic depression, generally half those of their non-affective counterparts
Summary
Schizophrenia and other psychotic disorders exhibit variation in incidence [1,2], prevalence [3] and course [4] along a number of dimensions, providing important signposts for clinical care, health service planning, etiological research and public health [5] Some of these, such as variation according to genetic risk [6], family history of mental illness [7,8] or declines in incidence with increasing age [9], are well-established and accepted in clinical and academic circles. We conducted a systematic review of incidence rates in England over a sixty-year period to determine the extent to which rates varied along accepted (age, sex) and less-accepted epidemiological gradients (ethnicity, migration and place of birth and upbringing, time)
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