Can LLM-Simulated Practice and Feedback Upskill Human Counselors? A Randomized Study with 90+ Novice Counselors

Training more counselors, from clinical students to peer supporters, can help meet the demand for accessible mental health support; however, current training approaches remain resource-intensive and difficult to scale effectively. Large Language Models (LLMs) offer promising solutions for growing counseling skills training through simulated practice and automated feedback. Despite successes in aligning LLMs with expert-counselor annotations, we do not know whether LLM-based counseling training tools -- such as AI patients that simulate real-world challenges and generative AI feedback with suggested alternatives and rationales -- actually lead to improvements in novice counselor skill development. We develop CARE, an LLM-simulated practice and feedback system, and randomize 94 novice counselors to practice using an AI patient, either alone or with AI feedback, measuring changes in their behavioral performance, self-assessments, and qualitative learning takeaways. Our results show the practice-and-feedback group improved in their use of reflections and questions (d=0.32-0.39, p$<$0.05). In contrast, the group that practiced with an AI patient alone did not show improvements, and in the case of empathy, actually had worse uses across time (d=$-$0.52, p=0.001) and when compared against the practice-and-feedback group (d=0.72, p=0.001). Participants' qualitative self-reflections revealed key differences: the practice-and-feedback group adopted a client-centered approach involving listening to and validating feelings, while the practice-alone group remained solution-oriented but delayed offering suggestions until gathering more information. Overall, these results suggest that LLM-based training systems can promote effective skill development, but that combining both simulated practice and structured feedback is critical.