Children born into families which split up before they are 16 are two and a half times more likely to develop schizophrenia in later life than those brought up by parents who stay together, psychiatrists leading the largest UK study into why people develop psychosis revealed yesterday.
The risk occurs if children have been separated from parents for at least a year, or if either parent dies, or both. It makes no difference which parent leaves, and the risk remains even if the child maintains regular contact with the absent parent. One in four children in Britain are brought up by single parents.
The finding - which flies in the face of the long-held assumption that schizophrenia and psychosis are purely genetic - emerged when researchers at the institute of psychiatry, King's College London, began looking into why African-Caribbean and African communities in Britain suffer from "remarkably high" rates of schizophrenia and manic psychosis.
The researchers, who had been investigating the incidence of psychosis among different ethnic groups in south London, Nottingham and Bristol, found that African-Caribbean people were nine times more likely to develop schizophrenia than white Britons and eight times more likely to develop manic psychosis. Black Africans were six times more likely to develop schizophrenia and six times more likely to develop manic psychosis. The rates were consistent for men and women, and across all age groups from 16 to 64. The standard risk for schizophrenia or psychosis is one in 100.
In determining the higher incidence, researchers led by Dr Craig Morgan looked at long-term separation from parents. "We found separation or loss of one or both parents before 16 was associated with a two to three increase in the risk of psychosis," said Dr Morgan. Long-term separation was almost twice as common in African-Caribbean communities compared with white British, with 31% of African-Caribbean families separating compared with 18% of white British families.
Dr Morgan, who compared 390 patients with 390 controls in the largest case-control study ever to explore the issue, said it was unclear whether it was the stress of separation, the stress of abuse that may precede this, or the poverty often associated with separation that was responsible.
"We don't know whether this is to do with the separation itself or to do with the associated social adversity - which we think is most likely" he said. He refused to predict that schizophrenia or psychosis would rise if the number of children in one-parent families increased: "Family breakdown may be particularly important [as a risk factor] when it's rare - when children's peers aren't in that situation."
