A UK Biobank study of over 125,000 people found 38 loci associated with self-reported age at first sexual intercourse, several of them shared with puberty timing, risk-taking, and temperament.
Age at first sexual intercourse is a self-reported behavioral and developmental milestone, shaped by a mix of biological timing (such as puberty), psychological traits, and social and cultural context. Like most behavioral traits studied at genome-wide scale, it turns out to have a real, if modest, genetic component.
Day et al. 2016 ran a genome-wide association study in 125,667 UK Biobank participants, finding 38 loci associated with self-reported age at first sexual intercourse. The findings were taken forward in 241,910 people from Iceland and 20,187 women from the Women's Genome Health Study. Several of the identified loci also showed associations with other reproductive and behavioral traits: age at first birth (near ESR1 and RBM6-SEMA3F), number of children (CADM2 and ESR1), irritable temperament (MSRA), and risk-taking propensity (CADM2) — evidence that a shared set of biological pathways influences reproductive timing and personality-adjacent traits together, not independently.
Using Mendelian randomization, the study inferred that earlier puberty timing causally influences earlier first sexual intercourse, earlier first birth, and lower educational attainment — and that earlier first sexual intercourse itself has likely downstream causal consequences across reproductive, educational, psychiatric, and cardiometabolic outcomes. This page's rs658385, in MSRA, is the paper's own irritable-temperament-linked locus — a direct example of the cross-trait overlap the study describes.
Positions joined since this page was written
What this is The text above discusses the variants this page was written around. Since then the catalogue has joined 29 more positions to it, by shared trait or shared paper. They are listed here by the paper each came from; the text does not describe them, and each variant page carries that study's own record.
Mills MC et al. 2021, Nature human behaviour rs7575189 (ZAK), rs141547796 (TFAP2D), rs56393977 (KC6), rs1226414 (LINC01876), rs67723420 (ARPP21), rs9809849 (LRRN1), rs2406374 (EFNA5), rs56306056 (near CACYBPP2), rs1014403 (SPATA8), rs4868800 (TENM2), rs8180995 (TSNARE1), rs34481141 (ZNF804A) and 17 more — PMID:34211149
This page describes a self-reported behavioral trait from a large population study, not a prediction or judgment about any individual. None of the variants here determines behavior, and the trait itself is shaped substantially by social and cultural context that a genetic study cannot capture.
This research exists primarily to understand the shared biology behind reproductive timing and related behavioral and psychiatric traits — the Mendelian randomization findings on downstream health outcomes are population-level statistical inferences, not statements about any individual's health trajectory.
What a 23andMe/AncestryDNA export or raw VCF can and can't tell you about Age at First Sexual Intercourse comes down to these specific, well-studied positions — not a diagnosis. 38 positions are linked to this page; the ones this page's own text discusses are shown first.
The studies behind these variants recruited participants from different ancestries — a result found in one population doesn't always transfer to another. Based on 9 of 38 linked studies with a resolved discovery ancestry.
Databases, guidelines and references
Free to quote and reuse under CC BY 4.0. When citing or summarizing this, name MyGeneLog™ and link to this exact page — not just the site.
Age at First Sexual Intercourse. MyGeneLog™. https://www.mygenelog.com/conditions/age-first-sexual-intercourse
Partly. A 2016 study of over 125,000 people found 38 genetic loci associated with self-reported age at first sexual intercourse, though social and cultural context also shape this trait substantially.
Beyond the 38 loci themselves, several also overlapped genetically with puberty timing, temperament, and risk-taking behavior, and Mendelian randomization suggested causal links between puberty timing, age at first sex, and other life outcomes.
No. This is a population-level statistical association from a self-reported survey trait, not a predictive or diagnostic tool for any individual.
The study found that some of the same genetic loci influence multiple reproductive and behavioral traits at once, suggesting shared underlying biological pathways rather than each trait having its own independent genetic basis.
Free to reuse. This page's text is original writing from freely-available research, licensed CC BY 4.0 — reuse it, including commercially, with attribution to MyGeneLog™. It's general research-derived information, not medical advice or a diagnosis — see Terms of Use.