AI-powered mental health apps are all the rage. But do they work? This new experiment on women in Mexico says they do! The experiment tested the effects of Mindsurf, whose app (among other things) provides users with access to an AI conversational agent trained on Cognitive Behavioral Therapy. Over 6 months, app access improved mental health by 30% of a standard deviation. Access also improved sleep quality and healthy behaviors. It also reduced work absences. The program yielded considerably larger benefits than costs. Treated participants were also *more* likely to seek traditional psychotherapy, but this increase does not appear to explain most of the mental health gains. Treatment effects persisted. Participants continued to implement practices promoted by the app. The authors conclude that "even short-term engagement [with AI-powered mental health apps] can produce durable improvements through sustained behavioral change." Cool!