What young parent has never heard himself criticized for spending too much time taking his baby in his arms or cuddling him at the slightest sob? Well, now science underlines, conversely, the biological virtues of the hug!
Cuddled, pampered, massaged or worn as a kangaroo, premature babies gain more weight while their brains develop better. And the benefit endures since, years later, they are more efficient in carrying out certain tasks and are more resistant to stress and anxiety.
But what is incredibly new is that the beneficial effects of cuddling would spread to the depths of the child’s cells, directly inscribed on his DNA. In November 2017, a team from the University of British Columbia, Canada, released the results of a study of more than 1,000 mother-child couples.
The researchers asked the mothers to fill in a “diary” in which they indicated the frequency of physical contact they had with their infant during the fifth week of their life, as the habits began to develop. Four to five years later, researchers compared the DNA of children who had a lot of physical contact with their mother to that of children who had little.
You should know that if the sequence of our DNA remains globally identical from one cell to another, it can, however, be expressed in very different ways due to subtle chemical modifications that take place around the molecule d ‘DNA. This is called epigenetics.
Genes passed over in silence
The Canadian team was particularly interested in an epigenetic modification called methylation (the addition of methyl chemical groups), which acts as a switch. If it is methylated, a gene is silenced and will not speak.
However, in the DNA taken from these more or less cuddled children, the researchers discovered differences in methylation at five different sites, including a gene coding for a protein involved in metabolism and another coding for a protein of the immune system. Even more astounding: the effects are observed in the long term. Five years after being lavished, the trace of the hugs is still visible on the genome of those who received them!
And that’s not all. In 2015, an English team conducted a study on children whose mothers had developed depression after their birth. Result: on the one hand, the team measured higher methylation rates of the NR3C 1 gene, linked to the body’s reaction to stress hormones. On the other hand, this effect of mothers’ depression on their children’s DNA is mitigated when mothers hug them a lot.
In other words, if the depression of mothers limits the activation of the NR3C 1 gene of their children, cuddling allows, conversely, to reactivate this gene! By what wonder? Because hormones, nervous signals or even epigenetic factors generated by the hugs would participate in this activation of the gene. With, ultimately, a decrease in the stress response.
A “kangaroo” effect
For now, studies have not been done far enough in humans to know whether touch has any effect on behavior or health. But precious clues come to us from research on premature babies! At the University of Miami, a physiological effect of massage has been found on children born too early. Massaged babies gain 47% more weight and, at 12 months, their mental development is also better.
In Israel and Canada, the “kangaroo” method is being studied – instead of being placed in an incubator, the newborns are carried against the parents’ stomachs. According to a study published in 2014, one hour a day for 14 days in the neonatal period is enough to improve the stress response, as well as the sleep and cognitive skills of the kangaroo children tested ten years later.
And in their brains, a Quebec team has observed greater efficiency in the networks of nerve fibers that carry information between the two hemispheres. In practice, it seems that massages work in several ways.
Mechanics first: the pressure receptors on the skin stimulate the activity of the vagal nerve and gastric motility. This may explain the weight gain of babies being massaged. In parallel, the production of growth hormone increases, probably by an epigenetic effect. As for brain development, we know that the brain responds according to the stimuli it receives: this is called brain plasticity. Physical contact therefore acts actively on its constitution.
If there is still much to discover on the epigenetics of touch, one thing is now scientifically established: cuddling our babies can only be beneficial to them.