"Family stress can disrupt puberty timing as well. Girls who from an early age grow up in homes without their biological fathers are twice as likely to go into puberty younger as girls who grow up with both parents. Some studies show that the presence of a stepfather in the house also correlates with early puberty. Evidence links maternal depression with developing early. Children adopted from poorer countries who have experienced significant early-childhood stress are also at greater risk for early puberty once they’re ensconced in Western families.
Bruce Ellis, a professor of Family Studies and Human Development at the University of Arizona, discovered along with his colleagues a pattern of early puberty in girls whose parents divorced when those girls were between 3 and 8 years old and whose fathers were considered socially deviant (meaning they abused drugs or alcohol, were violent, attempted suicide or did prison time). In another study, published in 2011, Ellis and his colleagues showed that first graders who are most reactive to stress — kids whose pulse, respiratory rate and cortisol levels fluctuate most in response to environmental challenges — entered puberty earliest when raised in difficult homes. Evolutionary psychology offers a theory: A stressful childhood inclines a body toward early reproduction; if life is hard, best to mature young. But such theories are tough to prove.
Social problems don’t just increase the risk for early puberty; early puberty increases the risk for social problems as well. We know that girls who develop ahead of their peers tend to have lower self-esteem, more depression and more eating disorders. They start drinking and lose their virginity sooner. They have more sexual partners and more sexually transmitted diseases. “You can almost predict it” — that early maturing teenagers will take part in more high-risk behaviors, says Tonya Chaffee, associate clinical professor of pediatrics at University of California, San Francisco, who oversees the Teen and Young Adult Health Center at San Francisco General Hospital. Half of the patients in her clinic are or have been in the foster system. She sees in the outlines of their early-developing bodies the stresses of their lives — single parent or no parent, little or no money, too much exposure to violence."