The Genain quadruplets are a set of identical quadruplet sisters with differing magnitudes of schizophrenia: Iris and Hester were both extremely disturbed whereas Myra and Nora where psychologically healthier. Being that they were identical, all sisters shared the same genes, the same genetic predisposition for schizophrenia, and the same family environment. Thus, the environmental factors that influenced the four girls must have varied to result in their varying severity of schizophrenia.
There are many factors that could explain the variation in the severity of the quadruplets' schizophrenia. First, their differences in weight after being born; Iris and Hester weighed much less than Myra and Nora- which could be due to differences in nutrition/health or how active the children were during childhood. Also, because Myra and Nora were born healthier, their mother favored them. This may have decreased their levels of affliction because although they were still schizophrenic, having a caring mother and being favored could have helped them develop more normally. Alternatively, the abuse suffered by Iris and Hester could have led to an increased severity of schizophrenia because they were not tended to with the same care as the other two.
The cause of the difference in magnitude of the schizophrenia of the quadruplets is still undetermined, but overall I think that the way that their mother treated them created the biggest impact. Being loved and cared for rather than abused and neglected clearly will result in differences in psychological health. This statement could be proven in a case study where researchers look at two different families: one with parents who are loving and put their child first and the other a malfunctioning family with abusive parents. The result of these behaviors would undoubtedly have an effect on the children and how they are raised; overall affecting their psychological health, for example: their self-esteem, independence, ability to make good decisions and many other behaviors.