To estimate how prevalent psychotic disorders are among adults living in private households in England, a two-phase approach was used. This involved a phase 1 screen followed by a phase 2 clinical assessment for some of the participants whose experiences or symptoms might indicate psychosis. Participants eligible for phase 2 were identified by meeting one or more of the following screening criteria at the phase 1 interview:
- currently taking any antipsychotic medication (orally or by injection)
- reporting an inpatient stay for a mental or emotional problem in the past 3 months, or having been admitted to a hospital or ward specialising in mental health problems at any time
- a positive response to question 5a (about auditory hallucinations) in the Psychosis Screening Questionnaire (PSQ), a series of 5 probe and 5 secondary questions about mania, thought insertion, paranoia, strange experiences, and hallucinations in the past year
- reporting symptoms suggestive of psychotic disorder (such as mood swings) and/or discussing such symptoms with a GP in the past year
- indicating they have or have had psychotic disorder (in answer to a direct question added to APMS 2014 about whether a participant thought that they had ever had any of a list of psychiatric disorders)
Overall, 6% of participants reported at least one of the above that might indicate psychosis, and so were eligible for a phase 2 assessment. Not all, however, could be assessed at phase 2. A fifth (20%) of phase 1 participants refused to be contacted for a phase 2 interview, and of those advanced to phase 2 with at least one psychosis criterion, 27% refused and 6% were non-contacts. Because much was known about the characteristics of non-responders to phase 2, a complex psychosis-specific weighting strategy could be developed to address non-response bias.
For the identification of psychotic disorder in the past year the following approach was used:
- for those who screened positive for psychosis at phase 1 and then had an assessment with a trained interviewer (a psychologist, for example), the results of the assessment were used
- for those who screened negative for psychosis at phase 1, it was assumed that these were true negatives regardless of whether or not a further assessment was completed
- for those who screened positive for psychosis at phase 1 but did not have a further assessment (due to refusal or non-contact, for example) a weighting strategy was applied to take account of non-response.
The weighting strategy meant that the assessment results for the participants assessed at phase 2 were weighted to reflect the profile of all participants identified as eligible. For example, a survey which contains 25% females and 75% males will not accurately reflect the views of the general population, which we know is around 50% male and 50% female. By adjusting the results of a survey in this way to make them representative of the population, weighting improves the accuracy of the results.
The achieved response rate (57%) is in line with that of similar surveys (Barnes et al. 2010; cited in APMS 2014).
The ‘Methods’ chapter of the Adult Psychiatric Morbidity Survey 2014 includes more detailed information on the weighting used.
The use of a survey to assess mental health conditions is not as reliable as a diagnosis made using a clinical interview. The assessments used have been validated, however, and are among the best available.
The survey covers people who live in private households. It doesn’t include those who live in institutional settings (such as hospitals or prisons) or in temporary housing (such as hostels or bed and breakfasts) or those who sleep rough. People living in such settings are likely to have worse mental health than those living in private households (Gill et al. 1996; cited in APMS 2014).
Where a selected participant could not take part in a long interview due to a physical or mental health condition, some information about this was recorded by the interviewer on the doorstep. This information may be biased due to it having been collected from another household member.
Socially undesirable or stigmatised feelings and behaviours may be underreported. While this is a risk for any study based on self-report data, the study goes some way to minimising this by collecting particularly sensitive information in a self-completion format.
The confidence intervals for each ethnic group are available in the ‘download the data’ section.
0.3% of White men surveyed screened positive for psychotic disorder. This is a reliable estimate of the percentage of White British men in England who are likely to screen positive for psychotic disorder. However, because the APMS results are based on a random sample of people aged 16 or older, it’s impossible to be 100% certain of the true percentage.
It’s 95% certain, however, that somewhere between 0.2% and 0.6% of all White men in England would screen positive for psychotic disorder. In statistical terms, this is a 95% confidence interval. This means that if 100 random samples were taken, then 95 times out of 100 the estimate would fall between the lower and upper bounds of the confidence interval. But 5 times out of 100 it would fall outside this range.
The smaller the survey sample, the more uncertain the estimate and the wider the confidence interval. For example, fewer men from the Black/Black British ethnic group were sampled for this survey than White men, so we can be less certain about the estimate for the smaller group. This greater uncertainty is expressed by the wider confidence interval of between 1.1% and 9.0%.
Suppression rules and disclosure control
Risk to disclosure has been accounted for with limitations of the level of disaggregation, size of category groupings, and the maintaining of large underlying populations for analysis. No further suppression or other disclosure control has been applied.
Percentages have been rounded to one decimal point.Quality and methodology information