Boys who grow up in hardship are more than four times as at risk of starting puberty aged 10 than those who grow up in safer, wealthier households.
And girls who grow up disadvantaged are twice as likely to start puberty early than others.
The startling findings, which may help explain why disadvantaged children are more likely to have health problems later in life, come from a new study by the Murdoch Children’s Research Institute, which surveyed 3700 Australian children.
Parents were asked to report on signs their children were going through puberty, which included growth spurts, pubic hair and skin changes. About 19 per cent of all boys and 21 per cent of all girls were classified as having reached early puberty.
But looking only at the children from severely disadvantaged homes, 36 per cent of boys and 33 per cent of girls were found to have reached early puberty.
That is compared with “average families”, where 20 per cent of boys and 21 per cent of girls went onto early puberty.
Lead researcher Ying Sun, a visiting adolescent health academic from China, said the findings could help explain the link between early disadvantage and health problems later in life.
“Multiple evidence shows early maturation links with emotional, behavioural and social problems during adolescence,” she said. “Also, it carries risk for reproductive tract cancers and cardiovascular diseases.”
The findings suggest that early-onset puberty may be an evolutionary response to trauma and struggle.
“When we are raised in sub-optimal living conditions that means we have a higher risk of premature death,” associate professor Sun said.
“That means maybe we will die before we’re successfully reproductive, so we would choose an adaptive strategy to mature earlier, to have our first baby earlier, and maybe we could have more kids to ensure our genes transfer to the next generation.”
Being born premature or being overweight may also influence when puberty starts.
Journalist Amanda Dunn has written The New Puberty, a book about children going through puberty earlier, which is due to be released in July. She says while scientists still do not know precisely what triggers puberty when it does, there is well-established evidence that early childhood stress and trauma can bring it forward.
“The hypothalamus in the brain is the trigger for puberty and it sends messages to the pituitary gland, and the pituitary gland then sends out puberty hormones that swing the testes and the ovaries into action,” she said.
“But we don’t know exactly why the hypothalamus swings into action when it does, that’s still unknown. The research shows that if a young person is under stress, under duress, they tend to mature earlier, probably simply in order to survive.”
The latest research, which surveyed children recruited at birth as part of the Growing Up in Australia study, was published today in The American Journal of Pediatrics.