<P> Some of the least understood environmental influences on timing of puberty are social and psychological . Nearly all of the research on these effects has concerned girls, partly because female puberty requires greater physiological resources and partly because menarche involves a clear threshold event that makes survey research into female puberty much simpler than male . In most of these studies menarche was specifically examined, assuming it to be a valid "proxy" for the more general process of puberty . In comparison with the effects of genetics, nutrition, and general health, social influences are small, shifting timing by a few months rather than years . The most important part of a child's psychosocial environment is the family . </P> <P> Some of the aspects of family structure and function reported to be independently associated with earlier menarche (antenatal and early childhood) </P> <Ul> <Li> Are non-white </Li> <Li> Experienced pre-eclampsia in the womb </Li> <Li> Are singletons </Li> <Li> Had a low birthweight </Li> <Li> Were not breast - fed </Li> <Li> Were exposed to smoking </Li> <Li> High - conflict family relationships </Li> <Li> The increased incidence of childhood obesity . </Li> <Li> Lacked exercise in childhood </Li> </Ul> <Li> Experienced pre-eclampsia in the womb </Li>

According to research all of the following are factors linked to the age of menarche