The WHO World Health Survey is a comprehensive international survey carried out across 70 countries, which uses face-to-face, telephone and online interviews to ask questions about the health of populations, public health risk factors, coverage and availability of health services and health care spending.

The survey includes a number of questions relating to mental health and the data is sometimes used by researchers to conduct research that investigates specific issues.

This cross-sectional study does just that; looking at the survey data to see if there is any relationship between psychotic symptoms and the general health status of the population in a specific country.

Over a quarter of a million people (55.9% women and mean age of 45 years) from 52 countries were involved in this study:

• 20 African countries
• 13 European countries
• 12 Asian countries
• 7 countries from the Americas

It’s important to stress that the survey did not set out to find clinical diagnoses of psychosis, but simply asked people about symptoms of depression and psychosis, as well as previous diagnoses of schizophrenia and current or previous treatment for schizophrenia.

General health status was assessed using a 16-point questionnaire and data were weighted and standardised so that comparisons across different countries were possible.

The survey used the Composite International Diagnostic Interview to ask single questions about psychotic symptoms during the previous year, which included:

• Hallucinations
• Experience of delusional mood
• Delusions of reference and persecution
• Delusions of control

The researchers carried out a logistical regression analysis to investigate the association between psychotic symptoms and overall health status. Here’s what they found:

• The prevalence of psychotic symptoms varied enormously across countries and symptom categories
• The overall prevalence of specific symptoms was:
  • 8.4% for delusions of reference and persecution
  • 7.1% for delusional mood
  • 5.8% for hallucinations
  • 4.8% for delusions of control
• 12.5% of survey respondents reported at least one psychotic symptom and 1.0% reported a previous diagnosis of schizophrenia
• All symptoms of psychosis produced a significant decline in health status after controlling for potential confounders

The authors concluded:

The prevalence of the presence of at least one psychotic symptom has a wide range worldwide varying as much as from 0.8% to 31.4%. Psychotic symptoms signal a problem of potential public health concern, independent of the presence of a full diagnosis of psychosis, as they are common and are related to a significant decrement in health status. The presence of at least one psychotic symptom is related to a significant poorer health status, with a regular linear decrement in health depending on the number of symptoms.

This type of research is fascinating but must be interpreted with caution, because the huge population included is so diverse and therefore very different from one another. Clearly a survey can tell us a huge amount about the health and lifestyle of different populations, but it is not the most reliable way of measuring disease prevalence or health status.

Link

Nuevo R, Chatterji S, Verdes E, Naidoo N, Arango C, Ayuso-Mateos JL. The continuum of psychotic symptoms in the general population: a cross-national study. Schizophr Bull. 2012 May;38(3):475-85. Epub 2010 Sep 13.