Daycare pseudoscience

Does daycare damage children’s brains? So say a growing number of commentators, particularly on the political right. Prominent daycare critic Mikhaila Fuller, daughter of Jordan Peterson, explained to her 1.3 million podcast followers that it affects children in ‘pretty nasty ways’, warning them against ‘traumatizing’ their children. Erica Komisar, an American psychoanalyst, claimed in 2025 on the popular podcast Diary of a CEO that daycare makes young children more likely to ‘develop pathological defenses’ in response to the ‘trauma’ of being separated from their parents. ‘It’s so bad for their brain,’ she continued, ‘and it’s been known to increase aggression.’

At the same time, the educational establishment views daycare as not only indispensable to child development, but also a solution to problems like inequality and violent crime. The European Commission says that preschool ‘lays the foundations for later success in life’. The World Bank claims that it can ‘help countries be more productive, and compete more successfully in a rapidly changing global economy.’ Governments around the world spend billions of dollars on daycare, notionally as an investment in future members of the workforce.

Who is right? Does daycare traumatize children or does it turn them into upstanding citizens? Or perhaps both are true, and daycare sacrifices the emotional health of toddlers in order to turn them into subdued salarymen.

Although the confidence with which they are made might suggest otherwise, there is little evidence to support such extreme claims on either side. It appears that whether a child attends daycare usually makes little difference to their outcomes.

Stress testing

Daycare skeptics like Komisar point out that levels of cortisol, colloquially known as the stress hormone, are raised in children at daycare. This may be true. Children in daycare have higher cortisol levels in their saliva and their cortisol levels seem to rise throughout the day. But this needs to be understood in context. Cortisol isn’t innately bad: it plays an important role in regulating metabolism and sleep-wake cycles. Without any cortisol in your body, you would die. Even in an unstressed person, cortisol levels fluctuate: peaking when waking up in the morning, before declining over the course of the day, with short-term spikes in response to things like exercise and socializing. And the relationship between cortisol and the experience of stress is not well understood. For instance, cortisol levels can be lower in people who report that they are chronically stressed. While higher cortisol levels at daycare could indicate that children are stressed, it could also mean they are excited or stimulated by novelty and social complexity.

Cortisol levels can change by an order of magnitude over the course of a day, which means it is easy to get completely different results for the same person from one day to the next. This, as well as variation by age and factors like how recently children have exercised or eaten, means that reliable data is hard to obtain. The studies we have may not be well powered enough to detect a genuine signal amid the noise.

We don’t need salivary cortisol to know that some children find daycare stressful. Perhaps they prefer to be with their parents or find the busy environment overstimulating. However, this is vastly different from the claim that daycare is traumatic and will permanently stunt a child’s emotional development.

On the Diary of a CEO podcast, Komisar went even further and suggested that the stress of being separated from their parents causes the amygdala, a small part of the brain involved in emotion, of daycare-attending children to ‘become active precociously’. The amygdala then supposedly ‘shrivels up and burns out because it cannot manage that stress so early’, leading to chronic anxiety, depression, and ADHD.

This is pure speculation. No one has done the research to make a claim like this. We don’t even know whether people with smaller amygdalas have them in response to trauma or if they are born like that. Komisar’s ideas may sound fringe, but she is a mainstream parenting commentator, with contributions to newspapers like The Wall Street Journal and television shows like Good Morning America.

Too good to be true

Anti-daycare commentators aren’t the only ones making overblown claims about its effects. Many politicians and policymakers confidently state that daycare is a panacea for all manner of social ills.

In 2013, then-President Barack Obama said that every dollar spent on childcare gives a seven-dollar return, which, if true, would be extraordinarily high, higher than most transport infrastructure and comparable to the gains from providing clean water in developing countries. Obama claimed that this effect is thanks to daycare ‘boosting graduation rates, reducing teen pregnancy, [and] even reducing violent crime’, and that attending daycare can cause children to ‘form more stable families of their own’. Hillary Clinton has said that ‘the evidence is overwhelming’ that spending on daycare ‘is good for economic development’. Joe Biden advocated for universal preschool to give America ‘the best-educated workforce’ in the world. Former New York mayor Bill de Blasio said that universal preschool would create ‘a more fair and just society’. Similarly, the British government has claimed that its recent expansion of subsidized daycare to nine-month-old babies will help them to ‘achieve better in school’ and promote their ‘future success [...] on the labour market’.

If these claims were true, daycare really would be a miracle intervention. But is it? Some of the most influential data on this topic comes from moderately sized observational studies commissioned in the 1990s and 2000s in Britain and the United States. These tested children’s academic and social skills at preschool age and later as they progressed into elementary school, finding that children who attended high-quality preschools performed slightly better on literacy and numeracy tests. But this early boost seems to fade by a few years into elementary school. The evidence is even more mixed on potential improvements to children’s social skills, with some studies finding children who attend daycare are slightly better at cooperating, while others find they have slightly more behavioral problems.

The clearest benefit is for children from disadvantaged backgrounds, which means children living with some combination of poverty, low parental education, single parenthood, or family instability such as foster care. Two famous studies (the Perry Project and the Abecedarian Project) from the 1960s and 1970s investigated the effects of intensive, targeted interventions for black children from especially deprived families living in segregated America. Researchers reported that children in these programs later had higher earnings and lower arrest rates. (The Perry Project was cited as evidence for Obama’s seven dollar claim.)

But both of these studies looked at children in very particular circumstances, who received not just ordinary daycare but intensive support that included free healthcare and home visits. Although the studies were randomized, they had small sample sizes of roughly a hundred children each, and their statistical methods were imperfect by modern standards. To suggest that universal daycare will deliver similar results in America today is, to put it generously, an audacious extrapolation.

Studies on daycare are usually observational rather than experimental. It is hard to randomize how children are looked after, which means it is hard to say whether effects are caused by childcare itself or by something else that is different about families that use it. One rare exception is a randomized controlled study from Tennessee in the 2000s, which investigated ordinary preschool education and followed children as far as high school. It reached similar conclusions to other studies on this topic: attending a standardized statewide preschool program benefited disadvantaged children, but the effects soon washed out as they entered school.

There are many potential reasons to subsidize childcare, like the fact that it means the taxpayer shoulders some of the cost of raising children. But if weakly evidenced improvements to children’s future earning potential are cited as a reason, this raises questions about whether public money is being properly spent.

Throwing the baby out with the bathwater

When we raise the bar for what counts as ‘good enough’ parenting, people tend to have fewer children. South Korea, where it is normal for children of all ages to be very intensively and expensively tutored outside school, has the lowest fertility rate in the world at just 0.8 children per woman.

Hysteria over daycare causes needless anxiety to parents and potential parents. A couple who believe that daycare is harmful may delay parenthood until they can afford for one of them to stay at home, or feel guilty if they do have to use daycare. Others may worry that the wrong choice of preschool could lead to a lifetime of educational disadvantage.

Commentators on the left and right have their own reasons to make sweeping claims on daycare. But by framing the debate in this way, they are misrepresenting science and causing needless worry. This may even prevent some children from being born at all.

Enough studies have been conducted on daycare that if there were large, lasting impacts on children, either positive or negative, we would probably know by now. On a population level, any effects of daycare are small enough not to be obvious. Families should be encouraged to do whatever works best for them without worrying that it will damage their children.