Age at First Sexual Intercourse, Genes, and Social & Demographic Context: Evidence from Twins and the Dopamine D4 Receptor Gene

Guang Guo, University of North Carolina at Chapel Hill
Yuying Tong, University of North Carolina at Chapel Hill

We carried out two distinct types of genetic analysis using data Add Health. The first was an exploratory non-DNA or biometrical analysis using MZ (305 pairs) and same-sex DZ (269 pairs) twins, which tells us whether there is an aggregate genetic contribution to age at first sex. Our second analysis investigated the association between age at first sex and the 48-bp repeat polymorphism in the dopamine receptor D4 gene (DRD4). Our biometrical analysis shows that MZ twins synchronize their timing of first sex to a much greater extent than the same-sex DZ twins. Our analysis of the polymorphisms in DRD4 indicates that those with an any-3R genotype experienced a risk of first sexual intercourse 23% (P=0.020), 240% (P<0.0001), 33% (P=0.003), and 55% (P=0.036) higher than those with an other/other (or any-4R) genotype in the all-ethnicities (n=2,552), Asian, white, and Hispanic samples, respectively.