title: Resemblance for age at menarche in female twins reared apart and together.
abstract: Menarche is a significant developmental event in the lives of young females. Genetic and family environmental influences on the timing of its occurrence are explored in the first formal analysis using reared-apart and reared-together monozygotic (MZA, MZT) and dizygotic (DZA, DZT) twin pairs. Mean age at menarche was 12.50 years (SD = 1.67) for the reared-apart pairs and 12.86 years (SD = 1.49) for the reared-together pairs. Intraclass correlations for age at menarche were 0.56 for MZA twins, 0.16 for DZA twins, 0.70 for MZT twins, and 0.41 for DZT twins. The mean within-pair difference was 1.07 years (SD = 1.04) for MZA twins, 1.67 years (SD = 1.59) for DZA twins, 0.64 year (SD = 0.86) for MZT twins, and 1.43 years (SD = 1.34) for DZT twins. These results are consistent with genetic influence, although the lower correlations for reared-apart twins and their larger within-pair differences suggest that age at menarche is partly affected by common rearing environments. Feeling understood by one's father during the growing-up years was significantly associated with earlier age at menarche, and a comparable trend was found for feeling understood by one's mother. These findings are considered with reference to current theories of pubertal timing.
authors.affiliation: Department of Psychology and Twin Studies Center, California State University, Fullerton, CA 92834, USA.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Segal
authors.forename: Joanne Hoven
authors.initials: JH
authors.lastname: Stohs
mesh_terms: D000293:Adolescent; D000375:Aging / Q000235:genetics* / Q000502:physiology; D002648:Child; D004777:Environment; D005260:Female; D006801:Humans; D008572:Menarche / Q000235:genetics* / Q000502:physiology / Q000523:psychology; D008910:Minnesota; D010287:Parent-Child Relations; D014429:Twins, Dizygotic / Q000502:physiology* / Q000523:psychology; D014430:Twins, Monozygotic / Q000502:physiology* / Q000523:psychology