In the past year, molecular geneticists have continued to exclude the involvement of particular candidate genes and chromosomal regions in schizophrenia. A Norwegian twin study has confirmed that non-paranoid schizophrenia appears 'more genetic' than paranoid schizophrenia, and a US family study suggests that the highest familial risk is to the relatives of female schizophrenics born between February and May. The prenatal viral hypothesis continues to provoke controversy. Two epidemiological studies suggest that those born or brought up in cities have a higher risk of schizophrenia than their rural counterparts.
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