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Rate of Psychosis Highly Variable between Countries - Suggests Strong Impact of Environmental Factors


Rates of psychosis can be close to eight times (800%) higher in some regions compared to others, finds a new study led by researchers at UCL, King’s College London and the University of Cambridge.

The study, published today in JAMA Psychiatry, was the biggest international comparison of incidence of psychotic disorders, and the first major study of its kind in more than 25 years.

“It’s well-established that psychotic disorders, such as schizophrenia, are highly heritable, but genetics don’t tell the whole story. Our findings suggest that environmental factors can also play a big role,” said the study’s lead author, Dr James Kirkbride (UCL Psychiatry).“We need more in-depth research to understand why people in some areas may be at greater risk of developing a psychotic disorder, which could help us understand the roots of the condition and guide health care planning,” he said.

The authors estimated the incidence of psychotic disorders across 17 areas in six countries - the UK, France, Italy, the Netherlands, Spain and Brazil - using comparable methodology. Their data was drawn from people aged 18-64 who contacted mental health services after a suspected first psychotic episode, which included 2,774 incident cases in total.

Study Web Site:

Past research has suggested that poor prenatal care (nutrition and stress during pregnancy), and adverse childhood experiences (stresses), likely are key factors in this variation in rates of schizophrenia in different parts of the world.

Related Reading:

Preventing Schizophrenia:

Toxic Stress in Childhood:

Toxic Stress of Poverty:

Adverse Childhood Experiences:The Lifelong Impact of Childhood stress:

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and another related study:

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Has there been any cross-cultural heritability studies on sz? Would that even be feasible? I did a Google search and didn’t find anything. I realize twin studies, family studies, etc. would be difficult to do cross-culturally, but it would be very interesting with some data on this.


Is this sort of what you’re looking for? see the references…


No, I mean heritability studies, where they compare the rates of sz with shared genetic heritance to estimate the degree to which variation in sz is attributable to individual genetic variation within that population.

I was hoping that maybe there was some way of doing that cross-culturally, although I’ve never heard of that.


Interesting idea - seems like a Meta study could be done without too much effort - comparing twins studies from different countries. I’ll keep an eye out for something like this…