While a stressful family environment in childhood has long been blamed for various psychological effects later in life, new research suggests that hostile situations at home may also have big physical implications for young girls.
In a study released Thursday, researchers at the University of Arizona and the University of Wisconsin-Madison looked at families of 227 preschool children, following them as they progressed through middle school. In particular, the researchers looked for the first hormonal signs of puberty in these children.
What they found was that parental support -- or lack of it -- may partially determine at what age young girls hit puberty. Specifically, young girls with families who were more supportive in preschool years tended to hit puberty later than their counterparts in less supportive family environments.
The research stops short of drawing a bold link between early stress and early puberty, as factors such as family income and other environmental factors may also be at play. But lead study author Bruce Ellis said that while it is still too early for parents to make solid conclusions based on the evidence, the findings hint at an interesting evolutionary link between sexual maturation and stress.
"Children adjust their development to match the environments in which they live," said Ellis, an associate professor in the Division of Family Studies and Human Development at the University of Arizona in Tucson.
"Children who grow up in environments that are dangerous and unpredictable tend to grow up faster," he said. "In the world in which humans evolved, danger and uncertainty meant a shorter lifespan, and going into puberty earlier in this context increased chances of surviving, reproducing and passing on your genes."
Julia Graber, associate professor of psychology at the University of Florida in Gainesville, said the study adds to a growing body of evidence linking early stress with the onset of puberty.
"It's an interesting topic, there has really been a lot of research coming out recently on this particular issue," said Graber, who was not affiliated with the research.
But she agreed with Ellis that too many unanswered questions still exist for definite conclusions to be drawn.
"As yet, there is no clear idea of why stress factors work in this way."
If one thing is certain, it is that early sexual development in girls is often a signal for other health consequences.
Past research has already shown, for example, that early puberty in girls increases the risk of various health problems, both physical and psychological.
"In today's world, early puberty in girls is a risk for many things, such as breast cancer, teenage pregnancy and depression," Ellis said. "Effective prevention strategies depend on understanding the factors that speed up puberty."
Graber said girls may be more susceptible to such environmental factors for the simple reason that, evolutionarily speaking, bearing children successfully goes hand-in-hand with favorable environmental conditions. Hence, she said, the female system is programmed to be more responsive to environmental cues.
Still, Graber added, the concept of stress leading to early puberty is in some ways puzzling.
"The body needs to be healthy in order to be pregnant, and stress seems to impact health negatively," she said. "What we're seeing is something that doesn't really fit in terms of what we'd expect."