一卵性双生児の一方にみられたDepressive Characterの1例

A Pair of Identical Twin Sisters of Whom the Elder was a "Depressive Character" (E. Kahn)

I．はじめに

　ある日米混血の女子学生が，短期間のうちに3回服毒自殺をはかった。彼女はふだん明朗活発な子として知られており，自殺企図の動機をさぐっても，取るに足らぬようにみえる，些少な動機がわずかばかり発見できただけであった。彼女を死に追いやろうとしたのは，一体何だったのであろうか。この素朴な疑問が，この女子若年患者との短期精神療法的な治療関係の中で絶えず，治療者の心の片隅に留まっていた。

　まもなく，患者には外見の非常によく似たふたこの妹のいることがわかった。治療者はこの妹と面接をするたびに，もしかしたら現在，自分の目の前にいる人が実は妹でないのではなかろうか，実は妹ではなくて患者自身が化粧を直し衣装を変えて出直してきたのではなかろうか，としばしば自問した。その後，卵性診断の結果，2人は一卵性双生児であることが判明した（表1）。

　The present report concerns a pair of identical twin sisters of whom the elder had been the heavier at birth, and who made repeated suicidal attempts and was diagnosed as a depressive character at the age of 21. Several environmental variables contributed to her depressive character and suicidal behaviors, among them the ego-effacing experiences of separation from her parents and alienation by the oparent surrogate during the early stage of her life appeared crucial. The importance of such an etiological study on suicides commited by identical twins is emphasized as well as this particular clinical study on the depressive character who had been masked with a so called "good hysterical facade" according to Zetzel until recently when the patient attempted suicides.

　This pair of identical twin sisters was a product of a mixed marriage between a Japanese mother and an American father. The patient's suicidal attempts were diagnosed as among those that were to be put into the high risk category of the criteria by Tuckman and Youngman of the Suicide Prevention Center at Los Angeles, California, U. S. A. As a depressive character, the patient manifested all the four clinical characteristics defined by Kahn, i.e., 1) low self-esteem, 2) dependent object relations, 3) chronic guilt and 4) self-directed aggression and masochism, although she also demonstrated an oversensitivity to separation and alienation as well as a sense of desperation.

　From the above, it was speculated that the patient's depressive character developed on the basis of her markedly deprived life history to which her separation from both her parents at birth and her grandmother's alienating attitude towards her seemed to be most contributory. Because the mother had to always stay away working for the family as her husband disappeared immediately after their twin children's birth, the grandmother started functioning as the parent surrogate for them. However, the grandmother's attitude was inclined to be unequal for the twin sisters mainly because 1) the younger twin sister was born prematurely and needed more love and care from the grandmother than did the patient herself, and 2) as a traditional Japanese woman the grandmother naturally expected the elder sister, the patient, always to give in to her yonger sister, even if she were not born prematurely.

　It was also clarified that despite of the fact that the twin sisters looked rather more like Americans than Japanese, the patient had developed a Japanese national identity whereas her younger sister had established an American identity. Thus, it was further speculated that the patient's conflict was due partially to transculturation, i e., transcultural interaction with her twin sister, and her own Japanese national identity which perpetuated her sense of desperation, that led her to her suicidal attempts, and that the Japanese society has not been necessarily as permissive to her as to her more mature younger sister who has been equipped with a secured American national identity.