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Assumptions used in estimating a population benchmark

The assumptions used in estimating a population benchmark for the treatment and management of schizophrenia in adults aged 18 years and older of 0.5%, or 500 per 100,000 population per year, and the assumptions used in estimating the expected number of acute episodes of schizophrenia of 165 per 100,000 population, aged 18 years and older, per year are based on the following sources of information:

  • epidemiological data on the prevalence of schizophrenia
  • hospital episode statistics data to establish the number of admissions for people with a diagnosis of schizophrenia
  • current practice to establish the number of people with schizophrenia in contact with GP services
  • published research on schizophrenia
  • expert clinical opinion of the topic-specific advisory group, based on experience in clinical practice and literature review.

For the purpose of this commissioning guide the adult population has been defined as people aged 18 years and older. Approximately 80% of the population in England is aged 18 years and older.

Epidemiological data

Prevalence estimates for schizophrenia in published literature vary widely and are known to be affected by a number of factors including social deprivation and ethnicity[1].

The survey on psychiatric morbidity conducted by the Office for National Statistics in 2000[2] found that the prevalence for probable psychotic disorder was 5 per 1000 (0.5%) adults aged 16 to 74, equivalent to around 197,000 people aged 18 years and older. A small percentage of these people will have psychotic conditions other than schizophrenia, and the figures will not include people who did not take part in this household survey, for example those living in temporary accommodation.

The survey on psychiatric morbidity conducted by the Information Centre in 2009[3] concluded that there was no change in the prevalence of probable psychosis between the 2000 and 2007 surveys, the figure remaining at around 0.5% of people aged 16-74 years.

Over a lifetime, about 1% of the population will develop schizophrenia. The lifetime prevalence of schizophrenia has also been estimated to range from between 0.4% and 1.4%[4].

Hospital episode statistics data

The 'Hospital episode statistics' (HES) database contains details of all admissions to NHS hospitals in England. It includes private patients treated in NHS hospitals, patients who were resident outside England and care delivered by treatment centres (including those in the independent sector) funded by the NHS.

Data were extracted to determine the number of people who were admitted to secondary care either as a planned or an emergency admission with a primary diagnosis of schizophrenia and related disorders in 2008/09. The international classification of diseases (ICD) (10th revision) codes used to extract the data were: F20, F21, F22, F23, F24, F25, F28 and F29.

Analysis suggests that around 26,100 people were admitted with a primary diagnosis of schizophrenia and related disorders.

Current practice

IMS Disease Analyser is a database that holds data from a sample of GP practice systems. Data were extracted from the database to assess the prevalence of diagnosed schizophrenia. Based on this data, the prevalence of schizophrenia among people aged 15 to 84 years is around 0.42%. This is slightly below previous estimates[2][3] and may be accounted for by coding issues in general practice.

Published research

To inform the report Helping people through mental health crisis: The role of crisis resolution and home treatment services (CRHT), the National Audit Office produced a model to assess the economic impact of integrating CRHT and inpatient services. The model assumes that for people with a psychosis, depression or anxiety disorder experiencing a crisis, overall, the percentage who are not admitted is 60%, with 40% being admitted.

Expert clinical opinion

NICE clinical guideline CG82 on schizophrenia recommends that cognitive behavioural therapy (CBT) should be offered to all people with schizophrenia. This can be started either in the acute phase or later, including in inpatient settings. The consensus opinion of the topic-specific advisory group is that 70% of those people offered CBT will take up the offer.

NICE clinical guideline CG82 on schizophrenia also recommends that family intervention should be offered to all families of people with schizophrenia who live with or are in close contact with the service user. This can be started in either the acute phase, or later, including in inpatient settings. The consensus opinion of the topic-specific advisory group is that:

  • around 50% of people with schizophrenia live with or have close contact with their families
  • of the 50% offered family intervention, around half would take up the offer
  • in total, around 25% of people with schizophrenia will take up family intervention.

Conclusions

Based on the epidemiological data and other information outlined above, it is concluded that a population benchmark for the treatment and management of schizophrenia in adults aged 18 years and older is 0.5%, or 500 per 100,000 population per year and that there are around 165 acute episodes of schizophrenia per 100,000 population aged 18 years and older, each year. These figures are based on the following assumptions:

  • the population prevalence of schizophrenia in adults is around 0.5%. This is equivalent to around 500 per 100,000 people aged 18 years and older or 197,000 people in England
  • the number of admissions to secondary care for schizophrenia and related disorders in 2008/09 was 26,100
  • admissions to secondary care account for around 40% of acute episodes experienced by people
  • adjusting for the 60% of acute episodes not admitted to secondary care gives an annual figure of around 65,300 acute episodes
  • there are around 39,400,000 people aged 18 years and older in England
  • there are therefore around 165 acute episodes per 100,000 people aged 18 years and older.

Therefore the population benchmark for the treatment and management of schizophrenia in adults is estimated to be 0.5% per year, with around 165 acute episodes per 100,000 population aged 18 years and older expected.

Use the service for the treatment and management of schizophrenia in adults commissioning and benchmarking tool to determine the level of service that might be needed locally and to calculate the cost of commissioning the service using the indicative benchmark and/or your own local data.

References

1. McCrone P, Dhanasiri S, Patel A et al. (2008) Paying the price: the cost of mental health care in England to 2026. London: The King's Fund

2. Office for National Statistics (2002) Psychiatric morbidity among adults living in private households, 2000. London: The Stationery Office

3. The Information Centre (2009) Adult psychiatric morbidity in England, 2007: results of a household survey. London: The NHS Information Centre for health and social care

4. Cannon M, Jones P (1996) Schizophrenia. Journal of Neurology, Neurosurgery and Psychiatry 61: 604-13

This page was last updated: 02 March 2012

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Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.