This is the research companion to We Took Away Play and Gave Them Therapy. Read the main post first.
Post 11 argued that the cultural response to anxious children (less independence, narrower home range, more confined play) has been the wrong move on the evidence, and that loss of independent play is a strong candidate cause for the developmental dysregulation getting medicalized. These five studies show what the wider Play literature is saying about risk, mobility, recess, neighborhood greenspace, and the broader childhood-loss-of-play argument.
When Adults Manage Risk, Kids Lose the Practice
Brussoni, M., Olsen, L. L., Pike, I., & Sleet, D. A. (2012). Risky play and children’s safety: Balancing priorities for optimal child development. International Journal of Environmental Research and Public Health, 9(9), 3134-3148.
DOI: 10.3390/ijerph9093134
What they found: Brussoni and colleagues reviewed the evidence on risky play (climbing, exploring, rough-and-tumble, age-appropriate independent activity) and what happens to children when adults engineer it out of childhood. They documented that risky play is associated with better physical activity levels, better social skills, better resilience, and crucially, no measurable increase in serious injury rates in the contexts where it has been allowed. Risk management strategies that prioritize zero-injury actually produce children who are less capable of assessing risk.
Why this matters for you: This is the clinical answer to the question parents already feel in their bodies. The protection has a cost. When adults manage the risk the kid was supposed to be learning to manage, the kid does not develop the muscle. The injury rates the helicoptering was supposed to prevent did not actually go up when kids were given the practice back.
What it doesn’t answer: Where the threshold sits for any individual child between productive risky play and genuine danger. The literature is clear that the line is real. It is less clear about how to draw it precisely for a specific kid in a specific neighborhood.
Risky Play Is How Fear Becomes Competence
Sandseter, E. B. H., & Kennair, L. E. O. (2011). Children’s risky play from an evolutionary perspective: The anti-phobic effects of thrilling experiences. Evolutionary Psychology, 9(2), 257-284.
DOI: 10.1177/147470491100900212
What they found: Sandseter and Kennair argue from evolutionary psychology that children seek out risky play (heights, speed, dangerous tools, real or perceived risk of getting lost or harmed) because the activities serve a developmental function. The thrilling experiences would calibrate a child's fear-processing system, in their model, the way exposure therapy calibrates an anxious adult's. Their 2011 paper is the canonical theoretical statement of this anti-phobic mechanism. The prediction that children with more risky-play exposure develop lower rates of anxiety has begun to receive empirical support from subsequent work (Dodd and colleagues, 2022), though the empirical literature is still building.
Why this matters for you: This is the theoretical scaffolding under the Post 11 argument. Risky play is not a luxury or a permissive parenting choice. It is anti-phobic training, built into the developmental program. Kids who do not get it are running a fear-processing system that has not been calibrated. The anxious-generation pattern starts to make a lot more sense once you read it.
What it doesn’t answer: How much risky play is enough, or which categories matter most. Sandseter has proposed taxonomies (heights, speed, tools, dangerous elements, rough-and-tumble, disappearance/getting lost) but the dose-response for each remains an active research question.
Recess Is Cognitive Maintenance, Not a Break From Learning
Pellegrini, A. D., & Bohn, C. M. (2005). The role of recess in children’s cognitive performance and school adjustment. Educational Researcher, 34(1), 13-19.
DOI: 10.3102/0013189X034001013
What they found: Pellegrini synthesized decades of recess research, including his own field studies, showing that children's classroom attention systematically declines with time-on-task and recovers with unstructured outdoor play. The deprivation-rebound effect is clearly stronger for boys. An age gradient (stronger benefit for younger children) follows from the cognitive immaturity hypothesis Bjorklund and Green proposed in the early 1990s, though the direct empirical evidence for an age effect is mixed. Schools that lengthened academic time by shortening or eliminating recess produced measurably worse attention and behavior, not better.
Why this matters for you: School districts that cut recess to extend instructional time did the opposite of what the cognitive science supports. Recess is not a luxury. It is part of how attention is restored to the working state needed for the next block of instruction. Every parent who has watched their child melt down after a no-recess day already knew this. The research catches up.
What it doesn’t answer: Whether structured physical education adequately substitutes for unstructured recess. The evidence suggests not (unstructured play has restorative effects that structured movement does not replicate), but the comparison has not been tested as carefully as it should be.
Childhood Greenspace Predicts Adult Mental Health
Engemann, K., Pedersen, C. B., Arge, L., Tsirogiannis, C., Mortensen, P. B., & Svenning, J. C. (2019). Residential green space in childhood is associated with lower risk of psychiatric disorders from adolescence into adulthood. Proceedings of the National Academy of Sciences, 116(11), 5188-5193.
DOI: 10.1073/pnas.1807504116
What they found: Using satellite data on residential greenspace exposure and linked Danish national health records, Engemann’s team tracked nearly one million individuals (N = 943,027) born in Denmark between 1985 and 2003, from birth to early adulthood. Children with the LOWEST greenspace exposure had up to 55 percent higher risk of being diagnosed with a wide spectrum of psychiatric disorders by adolescence and early adulthood, compared to children at the highest greenspace levels. The effect held after controlling for socioeconomic status, parental psychiatric history, and urbanization. The pattern was dose-dependent. More years of higher greenspace exposure produced lower risk.
Why this matters for you: Where a kid grows up changes the trajectory of their mental health into adulthood, and a lot of what makes the difference is access to outdoor space. This is a structural argument disguised as a parenting one. The individual family can move (sometimes) or maximize green-time at the margin. The bigger lever is what gets built, what gets zoned, what gets funded as a school district.
What it doesn’t answer: Exactly how greenspace produces the protective effect. The candidate mechanisms (physical activity, restorative attention, lower air pollution exposure, better sleep, stronger social networks) are all plausible. The Engemann paper does not isolate which ones do the work.
The Phone-Plus-No-Play Argument, and What It Misses
Haidt, J. (2024). The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness. Penguin Press.
ISBN 978-0593655030
What they found: Haidt synthesizes the rise in adolescent anxiety and depression across the developed world since roughly 2012 and argues for two principal causes: the smartphone-and-social-media shift, and the parallel decline in independent play and mobility. The latter is the part most relevant to Post 11. Haidt argues that overprotective parenting in the physical world combined with underprotective parenting in the digital world produced the worst-of-both-worlds developmental conditions.
Why this matters for you: Haidt has done more than any single author to bring the play-loss argument into the mainstream parenting conversation. The framework he puts forward (play-based childhood traded for phone-based childhood) is the parent-accessible version of the literature in this DD. Worth reading. Worth taking seriously. Worth holding alongside the methodological cautions below.
What it doesn’t answer: Establish causation cleanly. Critics including Candice Odgers and Andrew Przybylski argue Haidt's causal claims outrun the evidence. The trends are real. The size of the effect attributable specifically to smartphones versus other concurrent changes (less play, less independent mobility, climate anxiety, post-2008 economic conditions, the changes documented in this DD) is much harder to disentangle than the book sometimes suggests.
Coming Up
Our next Dive Deeper accompanies “The Grocery Store Is a Classroom.” Five studies on what guided play is, why it outperforms both free play and direct instruction, and what the parent-translatable mechanisms look like in practice.