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what causes stress during infancy? Laboratory and psychology research on animal and human infants gives us many clues. Certainly, pain from unfortunate medical conditions can create stress. So would pain from sensitivity reactions to formula or to foods passed along in breastmilk. Physical abuse and extreme neglect provide a very high degree of stress, but the effects of these severe cases are not the point of this text. Even short-term separation from mother leads to elevated cortisol in infants, indicating stress.1-2 In fact, after one full day of separation, infant rats already show altered brain organization of chemical receptors.3 A similar rat study revealed that one day without mother actually doubled the number of normal brain cell deaths.4
Animal findings demonstrate that isolation from mother, decreased skin stimulation, and withholding of breastmilk have biochemical and permanent brain consequences. Correlating these findings with human behavioral research suggests which events lead to chronic stress and its permanent consequences:
- allowing a child to “cry it out” without parental attention and affection.
- not feeding the child when hungry.
- not offering comfort when the child is disturbed or distressed.
- limiting body contact during feeding, throughout the day, and during stressful parts of the night.
- low levels of human attention, stimulation, “conversation,” and play.
When these occur regularly, they can lead to early chronic releases of high levels of stress hormones, as well as low expression of favorable hormones, as previously discussed. All these practices have been promoted during the last century in the form of scheduled feedings, “don’t spoil the child,” bottle feedings, which lead to propped bottles, and physical separation during the day and night.
While it is evident that genetic makeup and life experiences influence behavior, it has been demonstrated that experiences during infancy have the strongest and most persistent effect on adult hormone regulation, stress responses, and behavior.5 Research has demonstrated that high levels of early physical contact and maternal responsiveness can even mitigate genetic predisposition for more extreme stress reactions.6
Biological psychology researcher Megan Gunnar and her colleagues did infant studies that confirmed animal research findings. In their work, infants three months of age who received consistent responsive care produced less cortisol. Also, eighteen-month-olds classified as insecurely attached (who had received lower levels of responsiveness) revealed elevated levels of stress hormone.7 These same children at age two continued to show elevated levels of cortisol and appeared more fearful and inhibited. Again, these children were those who had been classified as having lower levels of maternal responsiveness. 8 Other investigations have confirmed these findings.9 Dr. Gunnar reports that the level of stress experienced in infancy permanently shapes the stress responses in the brain, which then affect memory, attention, and emotion.10