According to an article in the LA Times, the age at which a girl enters puberty is affected by her attachment to her first caregiver, usually the mother. New research in Psychological Science shows that poor mother-daughter attachment is linked to early onset of puberty, which is in turn related to an increased risk of cancer, depression, anxiety, and earlier sexual activity, increasing risk of STDs and teen pregnancy. Girls who were insecurely attached to their mothers were 2 1/2 times more likely to reach puberty early compared to girls who had strong attachments with their mothers.
Parenting aimed at creating a strong attachment- including breastfeeding on demand, baby wearing, co-sleeping, and responding to a child's cries- is so emotionally beneficial that its affects are seen in a child's physical well-being even years in the future. It reminds me of the unofficial mantra I hear at local La Leche League meetings: "A baby's wants are a baby's needs." Now there is evidence to prove that the attachment a baby wants is actually needed for good health later in life.