The weather in Quebec can be pretty unpleasant during winter and early spring. And yet, it was during the months of February, March, and April that over 500 children aged 10-12 were given classes outdoors for two hours each week in a gutsy experiment to see whether time in nature doing art, meditation, or learning about the environment could have an indirect impact on a child’s Mental health. Led by Dr. Tianna Loose from the Université de Montréal, her team randomized students to the outdoor intervention or classes as usual.

We’ve had suspicions for some time that putting our children outdoors away from screens and in close contact with nature had to be good for their Mental health. The spikes in anxiety disorders so many educators are dealing with in their classrooms had to have solutions. Low cost, and easy to implement, it turns out that time in nature with some structured programming can significantly decrease children’s self-reported symptoms of problems like depression and anxiety.

But—and this is a critical finding from the study—only those children who already scored above average for internalizing problems showed a significant change after the 12-week intervention. That doesn’t mean that the other children didn’t enjoy their time outdoors, or weren’t a little bit physically healthier, or more ready to learn, but those were not the factors studied by this team.

All of this reminds me of something I’ve termed “differential impact.” By that, I mean that the most disadvantaged, traumatized, and vulnerable children often benefit the most from our efforts to help them. It’s a pattern my own team has observed with regard to mindfulness training, too. Those kids with the most challenges are those who benefit most from Mental health interventions.

What that means in practice is that children whose lives are lived largely indoors, and online, are likely the kids who most need an outdoor classroom. Those children’s lives are not always of their own making. Overly stressed, extremely busy parents with bills to pay can inadvertently use technology to occupy a child who might otherwise benefit from time outside. Time outside can also be expensive.

It’s all and well to say, “Let your kids play outdoors”—but if one lives in a highrise, or your community lacks green spaces, “outside” may be more concrete and busy streets than the mythic suburb of leafy trees and sidewalks. Finding recreational activities that don’t cost a lot can be difficult.

Schools, on the other hand, often have access to the outdoors just beyond their front doors. For them, the cost (and risk) of taking kids outside is remarkably little.

The takeaway for parents and educators? The more depressed and anxious a child is, the more they need time outdoors.