ArticleArchives of sexual behavior2021
Reassessing the Effect of Older Sisters on Sexual Orientation in Men.
Article in Archives of sexual behavior, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 14 papers, 1 of them a synthesis that pooled it.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
14 citing papers in PubMed, 1 synthesis or guideline pooled it, 28 citations in OpenAlex.
- Pooled it
- Fraternal Birth Order Effect and Other Sibship Effects in Bisexual and Asexual Men and Women.Archives of sexual behavior · 2026Article
- A Pocket History of Research on Family Composition and Sexual Orientation.Archives of sexual behavior · 2026Article
- Reconsidering the Scope and Mechanisms of the Birth Order Effect on Sexual Orientation.Archives of sexual behavior · 2026Article
- Birth Order and Sibling Sex Ratio Predict Same-Sex Sexual Attraction in Iranian Cisgender and Transgender Adult Males and Females.Archives of sexual behavior · 2025Article
- Asexuality: Its Relationship to Sibling Sex Composition and Birth Order.Archives of sexual behavior · 2025Article
- Birth Order and Family Size of UK Biobank Subjects Identified as Asexual, Bisexual, Heterosexual, or Homosexual According to Self-Reported Sexual Histories.Archives of sexual behavior · 2025Article
- Testing Fraternal Birth Order Effects and Antagonistic Effects for Homosexual Men: Power Comparison of Various Methods.Archives of sexual behavior · 2025Article
- Examining the Fraternal Birth Order Effect and Sexual Orientation: Insights from an East European Population.Archives of sexual behavior · 2024Article
- Does the Fraternal Birth Order Effect Influence Handedness?Archives of sexual behavior · 2024Article
- Male androphilia, fraternal birth order, and female fecundity in Samoa: A 10-y retrospective.Proceedings of the National Academy of Sciences of the United States of America · 2023Article
- New Data on Birth Order in Homosexual Men and Women and a Reply to Vilsmeier et al. (2021a, 2021b).Archives of sexual behavior · 2022Article
- Estimation of the Fraternal Birth Order Effect in the UK Biobank Data Reported by Abé et al. (2021).Archives of sexual behavior · 2021Article
- Reassessing the Effect of Older Sisters on Sexual Orientation in Men.Archives of sexual behavior · 2021Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
2 authors at 2 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
This research reanalyzed questionnaire data from 8279 homosexual and 79,519 heterosexual men who participated in 2005 in an internet-based research project sponsored by the British Broadcasting Corporation. It focused on parameters of sibship composition (older brothers, older sisters, younger siblings) previously shown or hypothesized to influence sexual orientation in males. The results included the usual finding that older brothers increase the odds of homosexuality in later-born males. As predicted, older sisters also increase those odds, although by a lesser amount than older brothers. Other results confirmed that the odds of homosexuality are increased in only-children, the amount of increase being equal to that produced by one older brother and greater than that produced by one older sister. Finally, the results indicated that younger siblings have no effect on the odds of homosexuality in males. These results might be explained by the hypothesis that two different types of immune responses in pregnant women can affect the future sexual orientation of their male fetuses. One type of response affects fetuses in first pregnancies and reduces subsequent fertility. The other type affects fetuses in later pregnancies and has little or no effect on fertility. Finally, we conducted an estimate of combined sibship effects. Men who were exposed to any of the influences that we identified (being an only-child or having an older sibling) had 27% greater odds of homosexuality than did subjects who were exposed to none of these influences (i.e., the first-born of two or more children).
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.