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. 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 sp...