More threads by David Baxter PhD

David Baxter PhD

Late Founder
The Chemistry of Crying
August 5, 2004
by Holly Bennett,

Crying is no picnic for parents - or babies. Here's an inside look at this metabolically taxing activity.

Do you remember that buzzed, hyper-alert postpartum feeling - the way your baby's cry in the night would snap you out of sleep, heart pounding, no matter how tired you were? Partly, those were stress hormones you were feeling, and they were helping you become attached and attentive to your baby.

Alison Fleming, of the University of Toronto, has done some of the leading research into parental behaviour and hormone levels. One key hormone is cortisol: Like adrenaline, it's one of the so-called fight-or-flight hormones released in response to stress. They put the human system on a kind of red alert, ready to deal with emergencies.

Fleming found that women's cortisol levels tend to be elevated in the postpartum period. No surprise there - it is a challenging life transition. But she also found that women with higher levels of the hormone tend to be more attracted and attentive to their babies, and more sympathetic to their cries.

Fleming studied fathers too. Not only did their cortisol peak in response to an infant's cry, but first-time fathers tended to have a higher cortisol rise than experienced fathers. Same for moms. In both men and women, when the crying stopped, cortisol levels dropped.

Crying is no picnic for the baby, either.

Ronald Barr, director of the Centre for Community Child Health Research at the BC Research Institute for Children's and Women's Health, has studied the physiological changes that accompany crying. He explains that when babies cry, their heart rate increases, breathing patterns change, movements become uncontrolled. Perhaps most telling are increases of hormones, including cortisol, that are associated with stress - in the case of an infant, that stress may be from pain, hunger, fear or discomfort. What's not clear, says Barr, is whether the experience of crying is stressful, independent of the trigger.

We do know, however, that crying is a metabolically taxing activity. Intensive-care staff work hard to soothe premature babies when they cry because it can affect their breathing, oxygen concentration and blood pressure. Healthy infants are up to the physical challenge, but that doesn't mean it's OK for them to cry frequently, for long periods. Research suggests that chronic stress in babyhood (such as extreme neglect) can cause serious developmental deficits. By contrast, babies who are helped to calm down grow into children and adults who are less reactive and more adaptive in stressful situations.

It's an elegant system: the baby has stress and cries. The parent feels stress, takes care of the baby and the baby stops crying. The parent feels better. They both learn something good about their relationship. Add breastfeeding to the equation, and it works even better, because nursing moms release oxytocin, which tends to buffer the stress response.

There's a hitch, though: Babies, especially young ones, are not always easy to comfort. And that means stress can build up to unhealthy levels in the parents, with no relief in sight.

"Crying tends to increase over the first two months of life even if you're an optimal parent," says Barr, "and there's nothing worse than when you do everything right and it doesn't work." Helplessness, he points out, exacerbates stressful situations. Neglected babies experience this when their cries are ignored because they have no other way to help themselves. The parental equivalent is being unable to soothe an upset baby.

Colicky babies do more than their share of inconsolable crying, and on top of the sheer hard work and emotional stress of dealing with that, parents may feel awful about their baby's apparent anguish. But Barr says those parents should take heart: In his studies with babies, yes, the colicky ones cried twice as long and with double the intensity of their non-colicky counterparts, but the physical stress response was the same with both groups of infants. Which suggests, he concludes, - that they were not actually experiencing more stress than the other babies. That doesn't mean you don't need to comfort your colicky baby - your responsiveness is very important. But you probably don't need to worry about lasting trauma either.

Barr has a final word about the dark side of crying. When a hard-to-soothe baby meets a stressed-out parent, bad things can happen. "Parents need to know it is very dangerous to shake a baby. It's a recipe for disaster," he says. So if you feel you're about to lose control, take that feeling seriously. Put the baby somewhere safe, call somebody if you can, and do something (a shower, a walk, a good stress-relieving cry) to restock your resources.
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