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遺伝子が性格に影響する程度・割合は心理学で分析できない!? [論文]

最近はすっかり遺伝子ブームです。
血液型に限らず、遺伝子がどのように性格に影響するかという研究が数多く発表されています。
しかし、心理学の枠組みで「遺伝子と性格」や「血液型と性格」を分析すると、思いもよらない結果が出たりするので驚かされます。
ここでは、そういう不思議な現象を紹介しておきましょう。

「セロトニン」という名前を聞いたことがあるでしょうか? これは、性格に大きな影響を与える神経伝達物質の1つです。
神経伝達物質というのは、神経細胞から別の神経細胞へ情報を伝達する媒介となる物質のことです。
セロトニンの活性に関係する神経伝達物質である「セロトニントランスポーター」の遺伝子には、LL、LS、SSの3種類があり、種類によって性格に差が生じることが、多くの研究で確かめられています。
最近になって、この遺伝子の影響度を「アンケート調査」で比較分析してみたところ、心理学の「性格検査」より差が大きく出たという報告がありました。
つまり、遺伝子の影響を調べるには、心理学の枠組みにこだわりすぎると失敗する――というのは言い過ぎでしょうが、少なくとも心理学がアプリオリに正しいと考えてはいけないということです。

以下は、金澤正由樹さんの「B型女性はなぜ人気があるのか」からの抜粋です。

London School of Economics and Political Sceinece
New study is first to identify a "happiness gene" (2011)
http://www.lse.ac.uk/newsAndMedia/news/archives/2011/05/happiness_gene.aspx
☞任意のアンケート(幸福かどうか69% vs 38%) 効果量[影響の大きさ]:中(φ=0.3)
Lesch KP, Bengel D et al., Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region, Science. 1996 Nov 29;274(5292):1527-31.
☞心理学の性格検査(NEO-PI-R SD=0.29)効果量[影響の大きさ]:小~中(d=0.29)

血液型でも同じような現象が起きている。前著にも書いたが「ビックファイブ」という性格検査では、血液型による性格の差をうまく検出できないようなのだ。遺伝子と性格の関係は、意外に奥が深いようである。


B型女性はなぜ人気があるのか 30万人のデータが解く血液型の謎

B型女性はなぜ人気があるのか 30万人のデータが解く血液型の謎

  • 作者: 金澤 正由樹
  • 出版社/メーカー: 文芸社
  • 発売日: 2016/07/01
  • メディア: 単行本(ソフトカバー)

LSEの元記事はこちらです。

http://www.lse.ac.uk/newsAndMedia/news/archives/2011/05/happiness_gene.aspx

New study is first to identify a "happiness gene"

People tend to be happier if they possess a more efficient version of a gene which regulates the transport of serotonin in the brain, a new study has shown.

The findings, published today in the Journal of Human Genetics, are the first to show a direct link between a specific genetic condition and a person’s happiness, as measured by their satisfaction with life.

Jan-Emmanuel De NeveThis research led by behavioural economist Jan-Emmanuel De Neve, of the London School of Economics and Political Science (LSE), examined genetic data from more than 2,500 participants in the National Longitudinal Study of Adolescent Health (a representative population sample in the US). In particular, it looked at which functional variant of the 5-HTT gene they possess.

The 5-HTT gene, which provides the operating code for serotonin transporters in our neuron cell walls, has a variation (or allele) which can be either long or short. The long allele is more efficient, resulting in increased gene expression and thus more serotonin transporters in the cell membrane. Inheriting the gene from both parents, each of us will have a genotype which can be long-long, short-short or a combination of the two alleles.

The study compared the subject’s genetic type with their answer to the question “How satisfied are you with your life as a whole?” – to which they could give one of five possible answers: very satisfied, satisfied, dissatisfied, very dissatisfied or neither.

The results showed that a much higher proportion of those with the efficient (long-long) version of the gene were either very satisfied (35 per cent) or satisfied (34 per cent) with their life – compared to 19 per cent in both categories for those with the less efficient (short-short) form. Conversely, 26 per cent of those with the short-short allele were dissatisfied, compared to only 20 per cent of those with the long-long variant.

The study showed that possessing one long allele increases the likelihood of being very satisfied with life by 8.5 per cent as compared to having no long alleles of the 5-HTT gene. For two long alleles, the average likelihood of being very satisfied with life rose by 17 per cent in the study population.

Jan-Emmanuel De Neve said: “It has long been suspected that this gene plays a role in mental health but this is the first study to show that it is instrumental in shaping our individual happiness levels.”

“The results of our study suggest a strong link between happiness and this functional variation in the 5-HTT gene. Of course, our well-being isn’t determined by this one gene – other genes and especially experience throughout the course of life will continue to explain the majority of variation in individual happiness. But this finding helps to explain why we each have a unique baseline level of happiness and why some people tend to be naturally happier than others, and that’s in no small part due to our individual genetic make-up.”

The paper is entitled ‘Functional polymorphism (5-HTTLPR) in the serotonin transporter gene is associated with subjective well-being: evidence from a US nationally representative sample’ and is available at the Journal of Human Genetics (http://www.nature.com/jhg/journal/vaop/ncurrent/index.html) or from the LSE Press Office or the author.

A related paper prepared by Jan-Emmanuel De Neve and co-authors Nicholas Christakis (Harvard Medical School), James H. Fowler (University of California, San Diego), and Bruno Frey (University of Zurich) further develops this research and looks at the evidence produced from a study of twin pairs. This work shows that genetics explain about one-third of the variation in human happiness.

A TED talk on the link between genetics and happiness delivered by Jan-Emmanuel De Neve on March 18th, 2011 is now available online at http://www.youtube.com/watch?v=Po_YJZW7VJs

End

For more information, to interview the author or to request a copy of the paper, please contact:
Jan-Emmanuel De Neve J.C.De-Neve@lse.ac.uk
LSE Press Office +44 (0)207 955 7060 pressoffice@lse.ac.uk

Posted 6 May 2011

-----

参考までに、セロトニントランスポーターは、心配性の分散の3~4%を説明できる、というScienceに掲載されている論文を紹介しておきます。
なぜかタダで読めます。

http://www-psych.stanford.edu/~knutson/fop/lesch96.pdf

Science. 1996 Nov 29;274(5292):1527-31.
Association of anxiety-related traits with a polymorphism in the serotonin transporter gene regulatory region.
Lesch KP1, Bengel D, Heils A, Sabol SZ, Greenberg BD, Petri S, Benjamin J, M?ller CR, Hamer DH, Murphy DL.

Abstract
Transporter-facilitated uptake of serotonin (5-hydroxytryptamine or 5-HT) has been implicated in anxiety in humans and animal models and is the site of action of widely used uptake-inhibiting antidepressant and antianxiety drugs. Human 5-HT transporter (5-HTT) gene transcription is modulated by a common polymorphism in its upstream regulatory region. The short variant of the polymorphism reduces the transcriptional efficiency of the 5-HTT gene promoter, resulting in decreased 5-HTT expression and 5-HT uptake in lymphoblasts. Association studies in two independent samples totaling 505 individuals revealed that the 5-HTT polymorphism accounts for 3 to 4 percent of total variation and 7 to 9 percent of inherited variance in anxiety-related personality traits in individuals as well as sibships.
http://www.ncbi.nlm.nih.gov/pubmed/8929413
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