http://www.hawaii.edu/PCSS/announce/index.html
ミルトン・ダイアモンド
あなたは双生児？あなたは性転換者？
要約
ジェンダー・アイデンティティの発達に寄与する遺伝的およびその他の要因に関しては、依然として議論されている。この問題を明確にすべく、われわれはジェンダー・アイデンティティの一致不一致に関して双生児の調査を行った。文献調査では、性転換症の一致または不一致の32組（18組が男性、14組が女性）の一卵性双生児研究が得られた。さらにインターネットによる参加者募集と、著者の他の臨床家へのコンタクトにより、45組の新たな双生児が得られた。17組が男性の一卵性で、9組が女性の一卵性、8組が男性の二卵性、10組が女性の二卵性、1組が男女の双生児だった。
文献では、18組中12組(66.7%)の男性一卵性双生児が、性転換症のジェンダー・アイデンティティの一致例で、14組中4組(28.5%) の女性一卵性双生児が、性転換症のジェンダー・アイデンティティの一致例だった。我々の調査では、17組中7組(41.2%)の男性一卵性双生児が、性転換症のジェンダー・アイデンティティの一致例で、9組中2組(22.2%)の女性一卵性双生児が、一致例だった。18組の男性および女性の二卵性双生児の中では、男性の一組だけが一致例だった。
過去の研究とわれわれの研究を合計すると、35組中19組(48.7%)の男性一卵性双生児が、性転換症のアイデンティティの一致例で、23組中6組(26%) の女性一卵性双生児が、一致例だった。二卵性双生児の一致率はゼロに近かった。(25組中1組= 4%)
これらの知見は、性同一性障害の形成には、有意な遺伝的関与が存在することを示唆する。
（訳 by AJ）
ARE YOU A TWIN? ARE YOU TRANSSEXUAL?
Thank you for your help!
Some time ago, the following appeal for help was issued:
"It is now understood that among twins, there are sets in which both have transitioned gender and other sets in which only one has switched. Will you please help us try and find out why the differences? Your participation will augment the contributions currently on hand. This research was started some years ago but completion had to unfortunately be postponed. It is now being revived. Please help if you can."
We have now collected enough data to analyse, and have produced some interesting findings. So far we can only publish the abstract, but the full article will appear on this web site as soon as possible
Abstract
The relative contributions of genetic and other factors to the development of gender identity are still being debated. We studied twins that are concordant and discordant for gender identity status in order to provide clarification of this issue. An extensive literature search yielded 32 studies of monozygotic (MZ) twin pairs (18 male, 14 female) who were discordant or concordant for transsexualty. In addition, Internet requests for participants and clinical contacts of the author located 45 new pairs of twins: 17 monozygotic male pairs, 9 monozygotic female pairs, 8 dizygotic (DZ) male pairs, 10 dizygotic female pairs, and 1 male/female pair.
From the literature, 12 of 18 (66.7%) monozygotic male pairs were found to be concordant for transsexual gender identity and 4 of 14 (28.5%) female pairs were concordant. From our survey, 7 male monozygotic pairs out of 17 (41.2%) were identified as concordant for gender identity. Two of nine sets of female MZ twins (22.2%) were identified as concordant. Among 18 male and female dizygotic twin sets, only one male pair was found to be concordant for transsexuality.
Combining data from our independent findings with those from past research, 19 of 35 male monozygotic twin pairs (48.7%) were found to be concordant for transsexual identity and 6 of 23 (26%) female MZ twins were found concordant. In comparison concordance among either male or female DZ twins was close to zero (one of 25 = .04%)
These findings support the suggestion that there exists a significant genetic contribution to the development of gender identity disorder.
