... tend to spend more time together means that environmental factors are also indicated in this evidence. The concept that genetic factors are important in producing schizophrenia is supported by adoption studies. Tienari (1991) managed to find 155 schizophrenic mothers who had given up their children for adoption, and they were compared against 155 adopted children not having a schizophrenic parent. There was a large difference between these two groups, 10.3% of those with schizophrenic mothers had developed schizophrenia compared with only 1.1% of those without schizophrenic mothers. This suggests that genetics do play a part, but not completely based on genetics. Kety et al. (1978) considered adults who had been adopted at an early age between 1924 and 1947. Half had been diagnosed as suffering from schizophrenia and the other half had not. The two groups were matched on variables such as sex and age. The rate of schizophrenia was ...

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