The practice commonly used by mothers of leaving their baby to cry could put infants at risk for brain damage, according to claims from a child care expert.

Dr. Penelope Leach, author of the 1977 book “Your Baby And Child: From Birth to Age Five,” said Thursday that leaving a baby to cry without tending to them causes an increase of cortisol, known as the ‘stress hormone.’ Leach said too much production of cortisol could damage a baby’s brain, the Daily Mail reported.

“That doesn't mean that a baby should never cry, or that parents should worry when she does. All babies cry, some more than others. It's not the crying that is bad for babies - but crying that gets no response,” Leach said.

Leach’s comments were published Thursday in The Independent, and conflict with a research study by Australia's Murdoch Children's Research Institute published last month. The study concluded that allowing infants to cry had no negative effects on the child’s emotional or behavioral development.

Leach claims that the popular belief of allowing a baby to cry for up to 20 minutes alone helps them develop a sleep pattern, is not safe. She said babies do not have the ability to ‘learn’ when to go to sleep.

“It is not an opinion, but a fact that it's potentially damaging to leave babies to cry. Now we know that, why risk it?” she said.

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