What causes it, and how can we help kids?
© 2006 - 2013 Gwen Dewar, all rights reserved
Evidence of preschool stress
You send your child to preschool, hoping she will learn better people
skills. Instead, she comes back with new behavior problems--increased
rudeness, defiance, or aggression.
Spending lots of time with peers doesn’t seem to have improved her social skills. It’s made them worse!
It’s an experience shared by many American parents, according to researchers at Stanford and the University of California.
Drawing on a national database of over 14,000 children from
diverse backgrounds, Susanna Loeb and her colleagues examined the
effects of preschool attendance on academic skills, interpersonal
skills, self control, and rates of aggression.
The results were sobering. While center-based care raised reading
and math scores, it had a negative effect on social behavior. Kids who
began attending daycare earlier in life were more likely to develop
behavior problems. And there was evidence of a dosage effect, at least
for some groups. White children experienced increased negative effects
with just three hours of care per day, and the effects more than doubled
for kids attending at least 6 hours each day. African-American kids
didn't experience increased behavior problems unless they attended at
least 6 hours a day(Loeb et al 2007).
Similar results were reported by the National Institute of Child
Health and Human Development (NICHHD), which conducted a rigorous
longitudinal study on the effects of childcare on children under 5
(National Institute of Child Health and Human Development 2003).
Over a thousand children were tracked from infancy to kindergarten by investigators at over 20 prominent research universities.
Researchers found that the more time kids spent in non-maternal
care during the first 4.5 years of life, the more behavioral problems
Problems included defiance--like talking back, throwing temper
tantrums, and refusing to cooperate. They also included aggressive
behaviors--being cruel, destroying toys and other objects, and getting
into physical fights.
In addition, kids who spent more time in childcare were rated as
less socially competent by their mothers and kindergarten teachers.
What’s going on? We might guess that the problem lies with poor
quality preschool centers. But when Susanna Loeb’s group analyzed their
data, they found that middle- and high-income children – who presumably
attended better preschools – were among the most affected (Loeb 2007).
And another, more recent study of over 6,000 U.S. preschoolers found no
correlation between school quality and socioemotional outcomes (Keyes et
We might also wonder if the trouble is caused by too much time
away from parents. But again, the study by Loeb and colleagues doesn’t
support the idea.
In their data set, kids who received non-parental care outside of
childcare centers (for example, those cared for by grandparents or
nannies) did not suffer increased behavior problems.
So it wasn’t the absence of parents that made the difference. It was being enrolled in center-based care (Loeb et al 2007).
Two new studies may help us make sense of the puzzle. The first
followed the development of 600 American twins. The second analyzed a
huge database of over 75,000 toddlers in Norway.
New evidence: Only some kids at risk
The twin study is intriguing. Elliot M. Tucker-Drob and K. Paige
Harden (2013) were interested in the development of externalizing
behavior problems – defiance, aggression, and antisociality – so they
compared kids who did and did not attend preschool. How do genes and
environmental forces interact to produce more aggressive, difficult
The researchers found evidence that genes put some kids at higher
risk for developing externalizing symptoms. But child outcomes depend
on the environment, too: Kids at high genetic risk were more likely to
show externalizing behavior problems at age 5 if they had been enrolled
in preschool. Preschool attendance was not linked with externalizing symptoms among kids with a low genetic risk.
This, I think, is good news for people who want to improve the social effects of preschool. Something about non-center
based care has a protective effect on kids at high genetic risk for
developing externalizing behavior problems. If we can figure out what
that something is, we’ll have a better idea about how to improve
And here the Norwegian study might help. Henrik D. Zachrisson and
his colleagues examined behavioral problems and preschool attendance
among children between the ages of 18 and 36 months.
At first glance, the results were depressingly familiar. More hours
in center-based care predicted higher levels of bad behavior. But the
effect size was much smaller than it was in the U.S. studies, and the
link vanished altogether when the researchers tried a new method of
analysis: They looked for differences between siblings.
The reasoning went like this. Maybe daycare centers are
associated with behavior problems because kids at higher risk for
problems are more likely to get placed in center-based care. If so,
children within the same family might share similar risk factors, and
therefore exhibit similar behavior problems irrespective of the hours
they've spent in care. To test the idea, researchers examined families
where siblings experienced different amounts of center-based care. They
found no link between time spent in daycare and behavior problems
(Zachrisson et al 2013).
What should we make of this? First, Zachrisson’s team found
relatively little evidence of increased behavior problems to begin with.
Is that because Norway has a superior system of daycare? It’s very
plausible, as the researchers themselves note. In Norway, but not the
United States, children rarely begin center-based care before the age of
one. Centers are subject to national standards and regulations, and the
ratio of adult caregivers to children is very high. According to the
reports I’ve seen, the schools are play-based and emphasize the
development of social skills. Kids spend most of the day outdoors.
So if Zachrisson’s team found no evidence that preschool attendance causes behavior problems, that might be because preschool in Norway is better. If we want to improve preschool elsewhere, we might look to Norway to see what they are doing right.
But what about the alternative hypothesis? The idea that kids at
higher risk for developing behavior problems are more likely to be
placed in center-based care? Perhaps this can explain the results of the
American studies. Until somebody performs the relevant analysis, we
can’t be sure. But even if it turns out that preschools receive a
disproportionate share of high-risk kids, we’re still left with the task
The twin study suggests that preschool, as it exists in the
United States today, triggers aggressive behavior in susceptible kids.
But we’ve no reason to think the process is inevitable. As the authors
note, “genes for externalizing symptoms" did not increase a child’s
chances of developing externalizing symptoms by age 5 – not if he didn’t
attend preschool (Tucker-Drob and Harden 2013).
So what's protective about non center-based care? Maybe it's less stressful.
Daycare or preschool stress can be measured by the levels of
cortisol-—a stress hormone—-that children produce during the day. In
normal, healthy people, cortisol levels follow a daily rhythm, peaking
when they wake and then falling over the course of the day. Cortisol
levels are the lowest just before sleep (Sapolsky 2004).
But stress changes the pattern. If you are under stress, your
cortisol level rises, regardless of the time of day. In the short term,
this helps your body respond to the crisis. But chronic stress, and
chronically elevated levels of cortisol, can cause health and
developmental problems (Sapolsky 2004).
Because cortisol levels are easy to measure in young children,
researchers have collected samples from children who attend daycare and
children who stay home. In study after study, the results are the same.
When children stay home, their cortisol levels show the healthy
pattern--rising at waking and decreasing throughout the day. When
children attend daycare, the pattern changes. Cortisol levels increase
during the day (Geoffroy et al 2006).
Although it’s not entirely clear what aspects of preschool
attendance are distressing kids, some possibilities can be ruled out.
For instance, it’s not about being separated from parents. Kids
who receive home-based care do not have elevated cortisol levels, even
when their parents are absent (Dettling et al 2000). Nor is it about
differences in daytime resting. Kids in center-based childcare show
atypical cortisol patterns even after taking into account any possible
differences in napping or resting opportunities during the day (Watamura
et al 2002).
That leaves at least two (non-exclusive) possibilities. First,
kids in center-based care may be more distressed because they lack
daytime access to a secure attachment figure. It's relatively easy for a
child to form an attachment to a nanny or grandparent babysitter. It's
much harder to form attachments in a childcare center where staff are
overworked, lacking in sensitivity, or subject to frequent turnover.
When children do form such secondary attachments, their stress
hormone levels look more normal. In a study of 110 American
preschoolers, researchers found that kids with more secure attachments
to teachers were more likely to show the normal pattern of cortisol
changes across the day (Badanes et al 2012).
The second possibility is that kids are getting stressed out by
social interactions with other preschoolers. Megan Gunnar, a University
of Minnesota psychobiologist who has studied cortisol levels in
preschoolers since the 1990s, has expressed this view.
“There is something about managing a complex peer setting for an
extended time that triggers stress in young children"(ResearchWorks
It's an idea worth exploring.
What's wrong with peer socialization?
The question might sound wrong-headed. Surely we learn social skills
by interacting with other people. What could be more natural than
letting your preschooler loose in a social world of her own peers?
In fact, part of this reasoning is sound. You do need people to
learn people skills. The question is--which people? Preschoolers need to
learn self-control, empathy, compassion, patience, social etiquette,
and an upbeat, constructive attitude for dealing with social problems.
These lessons can’t be learned through peer contact alone.
Preschools are populated with impulsive, socially incompetent little
people who are prone to sudden fits of rage or despair. Young children
have difficulty controlling their emotions, and they are ignorant of the
social niceties. They also have less insight into the minds and
emotions of others (Gopnik et al 1999).
Yes, preschoolers can offer each other important social
experiences. But their developmental status makes them unreliable social
tutors. A child who copies other children may pick up good habits—-but
she may also pick up bad ones. And preschool peers do not always provide
each other with right kind of feedback.
When a child offers to share his toy with a caring adult, he gets
rewarded with gratitude and praise. He also learns that he will
eventually get his toy back. When he offers to share with a peer, he may
not get rewarded at all. Such experiences can undermine social
development by teaching the wrong lessons.
Moreover, it’s hard to see what’s natural about herding together a
bunch of children who are all the same age. From the evolutionary,
historical, and cross-cultural perspectives, it’s an unusual practice.
Preschool is an evolutionary novelty
Throughout most of human history, people lived in small foraging
bands of around 25 individuals. In such small groups, children rarely
had playmates of the same age. Socialization meant interacting with
people of all ages, from infants to grandparents (Konner 2005). In
modern foraging groups, children play in multi-age playgroups (Hewitt
and Lamb 2005) and may be watched over by multiple caregivers, including
older sisters and grandmothers (Hrdy 2005).
Even after the rise of agriculture, the “warehousing" of small
children would have been rare. Like foraging groups, village-based
communities are characterized by multi-aged playgroups and older sibling
caregivers. Historically speaking, segregating children by age is a
relatively new idea. It is favored in industrialized societies where
people lack the support of extended families and parents work outside of
What you can do
Spending long hours in center-based care can cause problems. But that
doesn’t mean that preschool can’t be a positive social experience. In
fact, kids benefit from opportunities to play with peers. The key is
balancing peer play time with sensitive caregiving. Here are some
specific tips on getting the best out of preschool or daycare.
Stay tuned into your child's needs
Time spent in daycare may affect your child’s behavior. But it’s not
the most important factor. The NICHHD study found that the most
important predictor of social competence was maternal sensitivity.
Sensitive mothers are warm and supportive. They understand their
children’s emotional needs and demonstrate respect for their children’s
autonomy. According to the NICHHD, the kids with the best behavioral
outcomes had mothers who scored highly on maternal sensitivity (NICHHD
Remain your child’s primary social tutor
See this article on preschool social skills.
These include talking to your child about her emotions and encouraging
her to form at least one friendship with a peer at school.
Avoid long hours by combining child-centered care with other quality alternatives
As noted above, there is mixed evidence about the effects of longer
hours no children's behavior. They probably depend on many things,
including the nature of your child's preschool, his personality,
heredity, and your cultural background. Until researchers sorts these
issues out, concerned parents might take precautions by reducing the
number of hours their kids spend in center-based care.
Find classes that are small and intimate
Find caregivers who can give your child warm, individualized,
personal attention. According to one study, the least stressful
preschool environments were small-scale--classes with no more than 15
students and 4 teachers (Legendre 2003).
It may be possible to create a harmonious, pleasant preschool
with a low staff-to-student ratio. Perhaps this happens in places like
Japan. But I haven't seen any studies measuring outcomes. Not yet.
Make sure kids have room to play
Look for preschools or daycare centers that provide ample space for
kids to play. Adults don’t like to be crowded. Neither do kids (Legendre
Look for teachers who expect friendly, polite behavior
Some schools are more permissive and laissez-faire than others. Avoid
schools that let kids get away with angry, antisocial or disobedient
Find out how your child's teachers cope with undesirable behavior
Psychologists like C. Cybele Raver recommend that preschool teachers
manage misbehavior in ways that minimize confrontation and coercion
(Li-Grining et al 2010). Teachers are advised to use reinforce desirable
behavior with praise and encouragement; to ignore inappropriate
attention-seeking behavior; to gently redirect kids who are going
astray; to give warnings about the consequences of breaking the rules;
and to use clear signals for keeping the whole class on task (like
turning the lights on and off).
More broadly, psychologists recommend the use of positive or
inductive discipline, an approach that emphasizes explaining the reasons
for rules and the consequences of bad behavior. Studies suggest that
preschoolers exposed to inductive discipline develop more self-control
and better social skills (Hart et al 1992).
Communicate regularly with your childcare providers
Find out what your child is doing at school. If your child is being
rejected by his peers—-or is involved in rejecting another child—-take
corrective action (see my article on
preschool social skills
). Similarly, get involved if your child is hanging out with a “bad
crowd." When preschoolers play in peer groups characterized by negative
emotions or anti-social behavior, their social development suffers
(Denham et al 2001).
References: Preschool stress
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Content last modified 2/13