Science tells us that when babies cry alone and unattended, they experience panic and anxiety. Their bodies and brains are flooded with adrenaline and cortisol stress hormones. Science has also found that when developing brain tissue is exposed to these hormones for prolonged periods these nerves won’t form connections to other nerves and will degenerate. Is it therefore possible that infants who endure many nights or weeks of crying-it-out alone are actually suffering harmful neurological effects that may have permanent implications on the development of sections of their brain? Here is how science answers this alarming question:

Chemical and hormonal imbalances in the brain
Research has shown that infants who are routinely separated from parents in a stressful way have abnormally high levels of the stress hormone cortisol, as well as lower growth hormone levels. These imbalances inhibit the development of nerve tissue in the brain, suppress growth, and depress the immune system. 5, 9, 11, 16

Researchers at Yale University and Harvard Medical School found that intense stress early in life can alter the brain’s neurotransmitter systems and cause structural and functional changes in regions of the brain similar to those seen in adults with depression. 17

One study showed infants who experienced persistent crying episodes were 10 times more likely to have ADHD as a child, along with poor school performance and antisocial behavior. The researchers concluded these findings may be due to the lack of responsive attitude of the parents toward their babies. 14.

Dr. Bruce Perry’s research at Baylor University may explain this finding. He found when chronic stress over-stimulates an infant’s brain stem (the part of the brain that controls adrenaline release), and the portions of the brain that thrive on physical and emotional input are neglected (such as when a baby is repeatedly left to cry alone), the child will grow up with an over-active adrenaline system. Such a child will display increased aggression, impulsivity, and violence later in life because the brain stem floods the body with adrenaline and other stress hormones at inappropriate and frequent times. 6

Dr. Allan Schore of the UCLA School of Medicine has demonstrated that the stress hormone cortisol (which floods the brain during intense crying and other stressful events) actually destroys nerve connections in critical portions of an infant’s developing brain. In addition, when the portions of the brain responsible for attachment and emotional control are not stimulated during infancy (as may occur when a baby is repeatedly neglected) these sections of the brain will not develop. The result – a violent, impulsive, emotionally unattached child. He concludes that the sensitivity and responsiveness of a parent stimulates and shapes the nerve connections in key sections of the brain responsible for attachment and emotional well-being. 7, 8

Decreased intellectual, emotional, and social development
Infant developmental specialist Dr. Michael Lewis presented research findings at an American Academy of Pediatrics meeting, concluding that “the single most important influence of a child’s intellectual development is the responsiveness of the mother to the cues of her baby.”

Researchers have found babies whose cries are usually ignored will not develop healthy intellectual and social skills. 19

Dr. Rao and colleagues at the National Institutes of Health showed that infants with prolonged crying (but not due to colic) in the first 3 months of life had an average IQ 9 points lower at 5 years of age. They also showed poor fine motor development. (2)

Researchers at Pennsylvania State and Arizona State Universities found that infants with excessive crying during the early months showed more difficulty controlling their emotions and became even fussier when parents tried to consol them at 10 months. 15

Other research has shown that these babies have a more annoying quality to their cry, are more clingy during the day, and take longer to become independent as children 1.

Harmful physiologic changes
Animal and human research has shown when separated from parents, infants and children show unstable temperatures, heart arrhythmias, and decreased REM sleep (the stage of sleep that promotes brain development). 10 12, 13

Dr. Brazy at Duke University and Ludington-Hoe and colleagues at Case Western University showed in 2 separate studies how prolonged crying in infants causes increased blood pressure in the brain, elevates stress hormones, obstructs blood from draining out of the brain, and decreases oxygenation to the brain. They concluded that caregivers should answer cries swiftly, consistently, and comprehensively. (3) and (4)

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