Male migrants living in cities are most likely to develop schizophrenia – a disorder which no longer affects equal numbers of men and women.

The mental illness is more variable than previously thought, according to a review into the incidence of schizophrenia, led by The University of Queensland’s Professor John McGrath.

It shows new cases of schizophrenia vary widely across the world – affecting at least 40 percent more men than women, 400 percent more migrants than native citizens and is more common in cities than urban/rural areas.

The review is the boiled down results of more than 160 scientific articles, reports and theses on schizophrenia from around the world, published since 1960.

Professor McGrath, from UQ’s Department of Psychiatry and the director of epidemiology at the Queensland Centre for Mental Health Research, and his team spent three years sifting through and translating the data.

He said the study was the first systematic review of new cases of schizophrenia and the results were “myth busters”.

“Schizophrenia does vary across sites, sex, migrant status and urbanicity,” Professor McGrath said.

“In the past, we have been lulled into a sense that schizophrenia does not vary. This was very misleading.”

He said some researchers had ignored the variation in the number of new cases believing the risk was the same in all places, within all groups.

He believed schizophrenia was more common in men than women possibly because boys’ brains were more vulnerable to disorders during development.

There is some evidence that oestrogen may also protect the brain.

Environmental factors such as infections, toxins, pollutants or lack of prenatal vitamin D, might explain the cases of schizophrenia in migrants and in cities.

The review is available at www.biomedcentral.com

For more information: Professor John McGrath (phone: +61 07 3271 8694, email: [email protected]) or Miguel Holland at UQ Communications (phone: +61 07 3655 2619, [email protected])