The demand for mental health support has skyrocketed, but access remains a challenge. Could AI step in to help? Researchers are exploring the potential of AI as counselors, focusing on Cognitive Behavioral Therapy (CBT), a widely used, goal-oriented therapeutic approach. However, training these AI counselors requires massive amounts of realistic conversation data—and therein lies the problem. Real counseling session transcripts are unavailable due to privacy concerns. A new research paper introduces CACTUS, a clever solution to this data dilemma. CACTUS is a large-scale, synthetic dataset that simulates realistic CBT counseling sessions. It’s built by carefully guiding large language models (LLMs) to act as both counselors and clients, emulating the back-and-forth of real therapy. The AI counselors in CACTUS are trained to select appropriate CBT techniques based on the client’s simulated persona and issues. These techniques help clients reframe negative thought patterns, a core component of CBT. CACTUS tackles the problem of generic AI responses by using detailed client profiles and varied attitudes (positive, neutral, negative). This allows the AI counselor to tailor its approach and offer more human-like support. To evaluate CACTUS, the researchers developed COUNSELINGEVAL, a framework for assessing the AI counselor's skills and the client’s emotional changes using established psychological metrics. The results show that models trained with CACTUS perform impressively in key counseling skills, including understanding, interpersonal effectiveness, and using CBT techniques. Interestingly, CACTUS helped improve the models in other counseling skills, too, including empathy, understanding, and helpfulness. However, there are challenges ahead. Current AI counselors in CACTUS still need help with asking insightful questions and offering truly personalized advice. Also, these simulated sessions are shorter than real-world therapy, and don't yet capture the complexities of multi-session counseling. Ethical considerations are paramount. The researchers stress that AI counselors are not meant to replace human therapists, especially for severe mental health issues. Instead, they envision AI as a supplementary tool, used under professional guidance. The research team behind CACTUS believes future AI counselors should focus on being skilled 'questioners' who guide clients to self-discovery, rather than simply offering quick solutions. This research opens exciting possibilities for increasing access to mental health support, while emphasizing the critical need for responsible AI development and human oversight in this sensitive area.