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.