[Psychopathological study of twin schizophrenia from the viewpoint of twin interaction]

Schizophrenia research requires both genetical and environmental approaches. Some researchers have studied the environmental aspects of schizophrenia by comparing schizophrenic twins with non-schizophrenic ones in discordant pairs. But few studies have taken notice of the interaction between twins. This article focused on the unique relationship between twins, "inter-twin community", which might be considered one of the most important environmental factors. This study included 14 pairs of twins, 28 people including 17 schizophrenic patients. These inter-twin communities were divided into "close type" and "distant type" according to the closeness between the twins prior to the onset of schizophrenia. The close type, in which there was a high degree of closeness, included 8 pairs of twins, 16 people, 11 of whom were patients. The distant type, in which there was a low degree of closeness, included 5 pairs, 10 people, 5 of whom were patients. An additional sub-class of the close type was the "close-competitive type". This sub-type had a high degree of closeness and a high degree of competition, and included 1 pair, both of whom were patients. Eight out of the 11 patients in the close type (72.7%) had an excellent prognosis. In this type of inter-twin community the relationships gave patients a strong and stable protective environment. In the close-competitive type, the twins supported each other while one twin was having difficulty, but fought with each other when they recovered and eventually one twin relapsed, resulting in an alternating pattern of schizophrenic episodes. The twins were unable to separate from each other and they both had a poor prognosis; thus their relationship both provided the patients with a degree of protection and had a marked harmful effect. In the distant type, 4 of the 5(80%) patients had an poor prognosis. In this type, when one twin became ill, the other twin did not support them, and the relationship provided little protective effect, resulting in poor outcomes. The findings in this study support the idea that the nature of the inter-twin community has a strong influence on the course of schizophrenia in twins. Additionally, since all the female pairs belonged to the close type, and the male pairs tended to be the distant type, there are probable gender differences in the types of inter-twin communities. Finally, in making therapeutic plans for twin schizophrenics, it is very important to consider their relationship in terms of the inter-twin communities.