After more than a decade of stability or improvement, adolescent mental health plummeted in the early 2010s. Rates of depression, anxiety, self-harm, and suicide rose dramatically, more than doubling on many measures. Why?

In The Anxious Generation, social psychologist Jonathan Haidt lays out the facts about the epidemic of adolescent mental illness that hit many countries at the same time. He then investigates the nature of childhood, including why children need play and independent exploration to mature and become competent, flourishing adults. Haidt shows how the “play-based childhood” began to decline in the 1980s, and how it was finally displaced by the arrival of the “phone-based childhood” in the early 2010s. He presents more than a dozen mechanisms by which this “great rewiring of childhood” has interfered with children’s social and neurological development, encompassing everything from sleep deprivation to attention fragmentation, addiction, loneliness, social contagion, social comparison, and perfectionism. He explains why social media harms girls more than boys, and why boys have withdrawn from the real world into the virtual world, with disastrous consequences for themselves, their families, and their societies.

Most importantly, Haidt makes a clear call to action. He diagnoses the “collective action problems” that trap us and then proposes four simple rules that could liberate us. He lays out steps that parents, teachers, schools, tech companies, and governments can take to end the mental illness epidemic and restore a more humane childhood.

Haidt has spent his career speaking data-backed truth into the most difficult landscapes—communities polarized by politics and religion, campuses battling culture wars, and now the public health emergency facing Gen Z. We cannot afford to ignore his findings about protecting our children—and ourselves—from the psychological harm of a phone-based life.