Stress in babies who are loved and well-cared for
You already know that terrible stressors – abuse and neglect – can alter development and have harmful effects on a baby’s brain. Perhaps you’ve also heard that emotionally supportive parents can protect children from very stressful environments.
For instance, growing up poor is a major risk factor for developing a variety of stress-related diseases. It puts kids at risk for accelerated aging of the chromosomes, and has even linked with smaller brain volumes (Asok et al 2013; Luby et al 2013). Yet studies suggest that sensitive, responsive parents can buffer – in some cases, perhaps even eliminate – these risks.
But what about less extreme situations? Stress in babies who live in safe, comfortable neighborhoods with loving parents? Does it really matter what parents do, so long as they are competent and caring? Do babies even notice subtle differences in parental care?
To some degree, a baby’s age is important. Experiments suggest that older babies, but not newborns, bounce back more quickly from mild stress when their caregivers show more sensitivity and understanding of their discomfort (Jansen et al 2010). Older babies are also more likely to get upset when they see their mothers adopt impassive facial expressions (Mesman et al 2009).
But even newborns have shown signs of distress when confronted by unresponsive, expressionless faces (Nagy 2008). As I note below, it’s also clear that newborns are calmed by certain types of affectionate, physical contact. And research suggests that babies develop different physiological responses to stress depending on their parents’ behavior.
In one study, babies born with risk factors for developing stress-related symptoms seemed to avoid these problems if they received lots of affectionate caresses during early infancy (Sharp et al 2012). In another study, babies with lower baseline stress hormone levels – and healthier stress response systems – had more sensitive mothers (Blair et al 2006).
So while young babies might not pick up on all our social cues, we
can still help them cope with stress. Those affectionate caresses could
be steering at-risk babies away from a lifetime of emotional problems,
and for some kids, sensitive parenting might make the difference between
success and failure at school.
When researchers tracked a group of easily-distressed, “difficult” babies over the years, they found that these children were particularly susceptible to the effects of parenting. Infants with relatively cold, insensitive parents ended up with the worst behavior problems. But babies with the most sensitive, emotionally responsive parents tended to become better-adjusted and higher-achieving than even those kids who had started life calm and laid-back (Stright et al 2008; Pluess and Belsky 2010).
Of course, the babies in this long-term study weren’t randomly assigned to receive either sensitive or insensitive parenting. That’s impossible for ethical reasons. But randomized experiments on mice support the idea that early nurturing has a lasting impact. Studies also indicate that children experience markedly different outcomes depending on the emotional support offered by their teachers. Such research outcomes, and everyday experience, suggest that babies benefit when caregivers who show high levels of sensitivity and emotional support.
What, in concrete terms, are sensitive, responsive parents actually doing that makes a difference?
How sensitive care affects a baby’s health and well-being
At a chemical level, affectionate touch and other nurturing behaviors appear to trigger the release neurotransmitters, like oxytocin and endogenous opioids (Kojima et al 2012; Weller and Feldman 2003). These have a direct, soothing affect, and also suppress the production of the stress hormone, cortisol (e.g., Albers et al 2008; Quirin et al 2011). Such changes promote a rapid recovery from stressful events, which reduces the “wear-and-tear” that stress hormones impose on the brain and body. They also put babies in a good mood, which facilitates learning and the development of positive social relationships.
But even without the “feel-good” brain chemistry, parents make a difference in other ways. Getting too cold, overhearing angry or fearful voices, being left alone in distress – all these situations can trigger the release of cortisol. So it stands to reason we can help babies by preventing stressful conditions from arising in the first place.
And that’s probably no small benefit. When babies seem upset, that isn’t just a sign they are physiologically stressed-out. It’s also a trigger of caregiver stress, which can put a strain on the parent-child relationship.
The baby in the bathtub
To see what I mean, take a simple mistake that Amie Hane and Lauren Philbrook (2012) have seen parents make during care-giving: Undressing a baby prior to preparing the bath.
Hardly an egregious parenting error, the researchers note. It’s not abusive or neglectful. But consider what happens next. The parent holds the naked baby in one arm while she readies the bath. The baby feels cold, squirms, and cries, which makes him more difficult to hold. The parent’s awkward grasp becomes even less comfortable, and, more abruptly than she originally intended, the mother plunks the baby down in the water, which feels particularly warm to the baby’s cold skin.
Now we’ve got an outraged, screaming baby, and a parent who is feeling stressed, inadequate, and frustrated. Her son seems to be very reactive and intolerant of change, and, for her part, the parent responds by becoming brusquer: She wants to get this over with. It’s the recipe for a vicious circle, one calculated to turn childcare into a series of stressful confrontations. Yet the whole conflict might have been avoided by a simple piece of advice. “Keep the baby clothed until just before you put him in the bath.”
Perhaps, then, parents can avert a whole cascade of negative effects by anticipating problems and taking measures to avoid them. Sensitivity and perspective-taking help parents do this, and research can help as well.
Let’s take a look at what scientific studies suggest about the way babies respond to touch, facial expressions, vocal communication, body language, carrying, diapering, feeding, and sleep arrangements.
1. Stress in babies and the complex nature of touch
As noted above, research demonstrates the biochemical effects of touch. Studies of mice suggest that nurturing touch triggers the release of endogenous opioids, natural pain-killers and sedatives, as well as oxytocin, a hormone that counteracts the effects of stress (Roth and Sullivan 2006; Stock and Uvnas-Moberg 1988).
What are the effects on human babies? When newborns were subjected to a painful medical procedure--a heel prick--they showed fewer signs of distress if they were held naked against their mothers’ bare skin (Gray et al 2000). Other research hints that infant massage can reduce stress hormone levels (Underdown et al 2006).
And as I mentioned above, a recent study suggests that frequent, affectionate touch can protect at-risk babies from developing overly reactive stress response systems. Consistent with this notion, a longitudinal study tracking 73 babies born pre-term found and assigned "kangaroo care" (daily skin-to-skin contact with parents) enjoyed a number of health advantages 10 years later, including an attenuated stress response and more advanced cognitive development (Feldman et al 2013).
Note, however, that touch isn’t always pleasant or helpful. Here are some research-based insights into the circumstances that make touch a more effective stress-buster:
Light caresses, which feel so pleasant to us, may not be pleasant to younger babies.
The system that relays information about touch from the skin to the brain is still developing during infancy, and it’s possible that a light caress or tickle feels quite different to young babies. In a recent brain scan study, researchers gently stroked babies on the palm of the hand with a piece of soft velvet (Kida and Shinohara 2013). Babies who were 10 months old experienced activity in the anterior prefrontal cortex, a part of the brain that processes rewarding stimuli. Younger babies (2-month-olds and 6-month-olds) did not. Evidence that light caresses aren't pleasant to some babies? Perhaps. In any case, experienced “baby whisperers” know this already, and offer good advice: If your baby seems to shrink from light touch, or shows other signs of distress, try touching her more firmly instead.
Sometimes infants don’t want to be touched at all, and if we ignore their cues we are likely to be a cause of stress, not the source of comfort.
Babies typically avoid your gaze when they feel over-stimulated, and expert baby handlers say it’s important to respect a baby’s desire for a “time out.” In one study, researchers observed mothers and infants as they played together, and noted whether or not mothers heeded their babies’ signals about being touched. Babies who received unwanted tactile stimulation had higher cortisol levels (Feldman et al 2010).
Gentle, slow, moderate pressure may be the key to effective infant massage.
For years, there has been some controversy about infant massage. While a number of studies indicate that medically-approved massage can be helpful to some preterm babies, the developmental benefits for full term, low-risk babies have yet to be proven (Bennett et al 2013). Researchers who advocate massage therapy think that moderate pressure may be crucial. When they reviewed the published evidence, they found that moderate pressure, but not light pressure, was linked with benefits (Field et al 2010). The take-home implication: If you’re interested in infant massage, go slow, be gentle, and apply moderate pressure.
Touch is more likely to soothe when it’s accompanied by other forms of affectionate contact.
You can imagine it would feel weird, and perhaps even stressful, if someone began stroking your arm without looking at you or making any other attempt to communicate. It’s likely that babies feel the same way. In one experiment, researchers assigned newborn babies to received one of three treatments:
• 15 minutes of tactile-only stimulation (in which the baby was stroked in silence, without being rocked or gazed at)
• 15 minutes of multisensory stimulation (in which the baby was touched, talked to, gazed at, and rocked) or
• no stimulation (the control group)
The researchers measured infant cortisol levels both before and after the intervention. The results? Whereas cortisol levels dropped for the babies in the multisensory condition, babies in the other groups actually experienced a rise in cortisol, and the steepest increase was associated with the tactile-only condition (White-Traut et al 2009).
2. The importance of facial expressions, tone of voice, and body language
Babies pay attention to faces immediately after birth, and, as noted above, are sensitive to your facial expressions. A large body of research indicates that babies prefer to look at happy faces, and are upset by displays of negative emotion (Moore et al 2009). They become distressed when their caregivers adopt wooden, unresponsive facial expressions, particularly if they themselves tend to be “high-strung” or have negative temperaments (Yoo and Reeb-Sutherland 2013). Recent research also suggests that 6-month old babies can distinguish between happy and angry body language (Zeiber et al 2013), and that babies exposed to angry adult arguments at home are at greater risk of developing abnormal stress response systems (Towe-Goodman et al 2012; Graham et al 2013).
3. Stress in babies and the soothing effects of movement
Babies like to be carried around, and seem to find it more soothing than being held by a person who doesn’t move. In a series of experiments, researchers found that infants experienced slower heart rates, reduced body movement, and reduced crying when they were held by an adult who was walking from place to place (Esposito et al 2013). Rocking may have similar effects.
4. Getting clean
I’ve already mentioned how bathing can be stressful for babies, and in fact babies typically experience elevated cortisol levels in response to being bathed (Jansen et al 2010). Diaper changes can also be distressing and put babies in a bad mood (Mörelius et al 2006), which presents parents with a dilemma. If your baby is falling asleep with a wet diaper, should you change him? You don’t want to get him riled up, but on the other hand the wet diaper might wake him up anyway. Happily, some researchers have addressed this question by injecting the diapers of sleeping infants with water. The babies didn’t wake up (Zotter et al 2007). Bottom line: Unless your baby has a skin infection, you might as well skip the stressful diaper change and let him sleep.
Does breastfeeding have distinctive, stress-busting effects?
Experimental studies of infants receiving immunizations have reported that babies showed less distress if injected during breastfeeding. But the same was true of babies who got shots while they fed from bottles (Shah et al 2012), so it’s not clear if the act of breastfeeding has any special soothing effects beyond those with holding, feeding, and skin-to-skin contact. On the other hand, there are hints that babies with a history of breastfeeding develop more resilience in response to stress. In a recent study, more weeks of breastfeeding predicted a faster recovery time from stress for 12-month-old babies (Beijers et al 2013).
More research is needed to confirm these results. Meanwhile, it seems possible that breastfeeding influences infant stress reactivity by helping mothers relate to their infants in a more relaxed and positive way. Breastfeeding induces chemical changes in a mother’s brain, improving her mood and her own stress reactivity, particularly in women who have breastfed more than one baby (Mezzacappa and Katlin 2002; Mezzacappa et al 2005; Tu et al 2006).
6. Sleep arrangements
It's clear that being left alone at night can trigger stress in babies. The outward signs are obvious. Babies cry. But research also suggests that babies who've been "trained" to accept their solitude continue to experience elevated cortisol levels, despite remaining relatively quiet (Middlemiss et al 2011).
So sleep arrangements have an immediate, short-term impact on stress in babies. Are there any other, more far-reaching effects? The World Health Organization recommends that infants under the age of 6 months sleep in the same room as their parents. This co-sleeping helps ensure that caregivers will be on hand if the baby is distressed or experiences a life-threatening event, and there may be other benefits too.
When researchers subjected 12-month-old babies to a social stressor – the so-called “strange situation” – they found that babies who had spent more weeks co-sleeping experienced less cortisol reactivity, even after controlling for other factors, like parental sensitivity and attachment security (Beijers et al 2013). Another study reports that 5-week-old infants with a history of co-sleeping already showed some evidence of greater calm. While co-sleeping history had no apparent effect on the babies’ responses to a painful vaccination, it was linked with less cortisol reactivity during bath time (Tollenaar et al 2012). The researchers speculate that having parents nearby at night may help babies regulate the stress response during the day.
For more about recent studies testing the effects of parenting on a child's developing stress response system, see my Parenting Science article, "The health benefits of sensitive, responsive parenting" as well as my blog posts, "Positive parenting protects kids from brain-shrinking stress?" and "Can a mother's touch reverse the effects of prenatal stress?"
In addition, if you know a highly reactive or "difficult" baby, be sure to read my post discussing the importance of alleviating stress in babies with very sensitive temperaments.
For a discussion of cultural biases against taking babies' distress seriously, see my blog post, "Babies can't remember is bunk," and my editorial about the way people often dismiss stress in babies as fussiness.
And to access my collection of Parenting Science articles about
babies, including evidence-based information about excessive infant
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Content of Stress in Babies last modified 11/13
image of sleeping baby © jarenwicklund /istock