Girls who are touched sexually at a young age hit puberty earlier than those who do not have sexual contact until later in life, a study has found.
The findings are part of a broader investigation to determine whether hormones or sexual experience trigger the onset of puberty.
Studying mice, German researchers found females who are touched on their genitals had changes their brain and puberty accelerated.
The researchers said the findings suggest sexual touch might have a bigger influence on puberty than previously thought.
And they warn it shows inappropriate sexual contact has a lasting impact on the brain.
Researchers saw significant cognitive changes in the brains of mice after sexual touch
Professor Michael Brecht, of Humboldt University in Berlin, said: ‘Sexual touch is strictly regulated in most human cultures and this is particularly true during development.
‘It has also become painfully clear that sexual abuse and inappropriate sexual contact during development have long-lasting detrimental consequences.
‘Presumably the long-lasting problems from inappropriate sexual contact during development reflect brain changes resulting from sexual experience.
‘Remarkably, structural brain imaging in humans with a history of sexual abuse identified a thinning of putative human genital cortex, as a cortical consequence of childhood sexual abuse.’
Professor Brecht worked with PhD student Constanze Lenschow to explore the beginning phases of puberty.
They noted that we have long-known that social cues can either accelerate or delay puberty in mammals.
But it hasn’t been clear which cues are particularly triggering, nor how they affect the body and brain, or even reorganize the brain.
They observed the neural representation of the genitals in the cerebral cortex expands during puberty.
To begin with, the study confirmed what was expected in that sexual hormones accelerate puberty and the growth of the so-called ‘genital cortex’.
However, what’s new is that they found sexual touch also contributes substantially to the acceleration of puberty.
The study put young female rats together with male rats and found the genital cortex expanded as a result.
Yet this didn’t happen when the males were separated from them by wire mesh, thereby preventing direct contact.
However, they found that the same acceleration of cortical expansion could be observed when the rats’ genitals were touched artificially using a lubricated brush.
Lenschow said: ‘The effects of sexual touch on puberty and the genital cortex are remarkable since you wouldn’t expect this area of the brain to expand at this stage of development.’
This suggested the expansion of the genital cortex is not only triggered by hormones but also by sexual touch.
Prof Brecht added: ‘The representation of the body changes in the cerebral cortex and in particular the genital cortex doubles in size.
‘Our results help to understand why the perception of our body changes so much during puberty.’
Changes of the body and the concurrent changes in the brain during puberty are not merely a matter of hormones – they are also co-determined by sexual experience.
The study was published in the journal PLOS Biology.