New systematic review shows how the incidence of schizophrenia and other psychoses has changed since 1950

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This is one in a series of 5 systematic reviews commissioned by the Department of Health, which seek to establish a comprehensive understanding of the distribution and pattern of psychotic disorders in England, between 1950 and 2009. All mental health professionals, commissioners and health planners will find this research relevant to their work.

It’s well established that schizophrenia and other psychoses affect people to varying degrees and some of the reasons for these differences are controversial and hotly debated. For example, research has shown that ethnicity, migration, place of birth and upbringing all influence the incidence of these health conditions.

The reviewers who conducted this research are from Cambridge University and the Institute of Psychiatry. They found 83 citations to include in their meta-analyses. Most of these studies were cross-sectional, which means that the opportunities to show a causal link between epidemiological factors and illness are very limited.

Participants included were adults (16-64 years) with a range of conditions:

  • First-onset psychosis (including non-affective psychoses)
  • Schizophrenia
  • Bipolar disorder
  • Psychotic depression
  • Substance-induced psychosis

The review was conducted using the reliable methods of the Cochrane Collaboration and the PRISMA Statement.

Here’s what they found:

  • The incidence rates were:
    • All psychoses – 31.7 per 100,000 person-years (95%CI: 24.6–40.9)
    • Non-affective psychoses – 23.2 (95%CI: 18.3–29.5)
    • Schizophrenia – 15.2 (95%CI: 11.9–19.5)
    • Affective psychoses – 12.4 (95%CI: 9.0–17.1)
  • There was a secondary peak onset for psychosis risk in women after 45 years
  • Several ethnic minority groups had higher rates of most disorders than the white (British) population, e.g. relative risk 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)
    • South Asian groups in England (pooled RR: 2.4; 95%CI: 1.3–4.5; N=3)

The authors concluded:

Incidence 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.

It’s worth noting that the research team have opened up their data set and made it freely available as a source of further information for readers and also as a data set for other researchers.

Links

Kirkbride JB, Errazuriz A, Croudace TJ, Morgan C, Jackson D, Boydell J, Murray RM, Jones PB. Incidence of schizophrenia and other psychoses in England, 1950-2009: a systematic review and meta-analyses. PLoS One. 2012;7(3):e31660. Epub 2012 Mar 22.