The finding is based on a study conducted by researchers at the University of Arizona and the University of Wisconsin-Madison who analysed the effects of stress on families of 227 preschool children over a period of time.
They used a 1991 model developed by researcher Jay Belsky and colleagues that shows how family ecology speeds up or slows down puberty in girls. According to this theory, children's early experiences affect how they mature, with certain stressors in and around the family creating conditions that speed puberty as well as sexual activity.
These stressors include marital conflict, negativity and coercion in parent-child relationships, and lack of support between parents and children. As part of the new study the researchers looked at the families' socioeconomic conditions, marital conflict, parental depression, and supportive versus coercive parenting, through interviews with both mothers and fathers.
The study followed the children through middle school, testing the first hormonal changes of puberty-the awakening of the adrenal glands-in 120 of the children (73 or whom were girls) when they were in first grade, and the development of secondary sexual characteristics-such as breast budding and the growth of body hair-in 180 girls when they were in fifth grade.
Based on this the found that kids living in families with greater parental supportiveness, from both mothers and fathers, and less marital conflict and depression - but only when reported by fathers - experienced the first hormonal changes of puberty later than other children, the researchers found.
In addition, kids whose mothers had started puberty later (a genetic factor), whose families were better off when the children were in preschool, whose moms gave them more support when they were in preschool, and who had lower Body Mass Index (BMI) when they were in third grade developed secondary sexual characteristics later than their peers.
"Consistent with the theory, quality of parental investment emerged as a central feature of the proximal family environment in relation to the timing of puberty," said to Bruce J. Ellis, associate professor of family studies and human development at the University of Arizona and the lead author of the study.
"These results replicate and extend previous longitudinal research indicating that higher levels of positive investment and support in family relationships in preschool predict lower levels of pubertal maturation in daughters in the seventh grade."
The findings appear in the November/December 2007 issue of the journal Child Development.