Comparing Human and AI Therapists in Behavioral Activation for Depression: Cross-Sectional Questionnaire Study.

Background: Large language models (LLMs) have rapidly advanced across numerous fields, including mental health care. A shortage of trained therapists and mental health care providers has driven informal use of LLMs for therapeutic support. However, their clinical utility remains poorly defined. Objective: This study aimed to systematically evaluate and compare the therapeutic knowledge and single-turn response capabilities of LLMs versus psychotherapists in training in the context of behavioral activation (BA) therapy for depression, and to assess how both groups' performance changed when provided with structured therapeutic training materials. Methods: Six LLMs and 8 human participants completed a questionnaire on depression and BA with 20 multiple-choice items and 10 therapy scenarios, each with 3 open-ended items, that postulated empathic response, use of validation strategies, and theory of mind capabilities. Human participants completed the questionnaire before and after a 5-hour workshop and 5-week period with learning materials. The LLMs received identical training content as context during the second test. All open-ended questions were rated on 5-point scales by 2 experts. Results: At baseline, the LLMs demonstrated higher knowledge scores than human participants (61.0 vs 52.0 out of 100 points) and were rated higher in empathy (U=2.0; P=.005; r=0.917), validation quality (U=2.5; P=.006; r=0.896), anticipation of cognition (U=0.0; P=.002; r=1.000), and anticipation of emotion (U=0.0; P=.002; r=1.000). Following BA training, the LLMs maintained their performance advantage across multiple-choice and open-ended items. Conclusions: The results suggest that LLMs may generate high-quality therapeutic single-turn responses that integrate clinical knowledge with empathetic communication. The findings hint at LLMs' potential as valuable tools in mental health care, although further clinical trials are needed to evaluate their performance in ongoing therapeutic relationships and clinical outcomes.