A teenager who has said almost nothing in a year of weekly counseling stands at the base of a rock face, harnessed, being asked to climb. Her hands are shaking. The therapist is not across a desk but a few feet away, holding the rope. Something in the setup—the fear, the trust required, the fact that there is nowhere to hide behind a phone or a shrug—does what the therapy room could not. She climbs. That evening, around a fire, she talks.

This is the wager at the heart of adventure therapy: that some people heal more readily through doing something hard and real in the outdoors than through sitting and talking about it. It used to be a fringe type of therapy, but…