Family studies are important to scale the amount biological vulnerability in schizophrenia. It's a process to identify hereditary developments for a child. Another way of studying the effects of heredity on development of schizophrenia is through adoption studies. There are two basic kind of adoption studies. The first type compares adopted children whose biological parents were diagnosed as having schizophrenia with adopted children whose parents did not have this disorder. The second examines the incidence of schizophrenia in the biological and adopted families of adopted children who later develops this disorder.
The complexity & value of adoption studies is illustrated by a study conducted in Finland by Tienari et al., 1990. Adopted kids whose biological mothers were diagnosed with schizophrenia were paired with adopted kids whose biological parents didn't have this diagnosis. In order to carry out this study, researchers collected information about nearly 20k women who had been treated in psychiatric hospital at some time during a 10 year period. From this group, they found 171 women who had been diagnosed with schizophrenia & who gave birth to a child who was adopted by a non related Finnish family before the child was 4 years old. Fewer than 1 in 100 of original cases qualified.
Some other tasks the researchers faced:
1. Selecting 2 adopted children as matched controls for each index case.
2. Checking the psychiatric histories of control children's parents.
3. Administering structured interviews to all the biological mothers, thus providing a diagnosis to compare with that in hospital records.
4. Interviewing the biological fathers of each index group member to evaluate whether he also had a psychiatric disorder that would add some risk for the child.
In addition, the team performed rearing environment evaluation .
1. Interview with entire family.
2. Joint interview with both adoptive parents.
3. Psychological testing.
4. Comprehensive test battery for each one separately.
5. Follow up & assessment for 5 to 7 years.
The study's findings support the idea that healthy family environment has a protective effect on kids who may be at a risk of schizophrenia. In the group of index children reared in psychologically healthy families, none had become psychotic & only 4% had severe psychological disorder. Index children brought up in severely disturbed families, 11% were psychotic & 41% had sever borderline state or severe psychological disorder. The index children were more likely to have a psychosis compared to the controlled children with each corresponding family type. These findings support the view that genetically transmitted vulnerability may be necessary for or at least increase the possibility of occurrence of schizophrenia.
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