Monitoring Clinically Relevant Behaviors and Experiential Avoidance Throughout the Course of Acceptance and Commitment Therapy: A Single-Case Quasi-Experimental Study

The present single-case quasi-experimental study monitored changes in target behavior and experiential avoidance (EA) in an individually delivered, 10-session weekly acceptance and commitment therapy intervention. Participants were three university students with elevated EA who endorsed varying mental health concerns. Primary outcome and process variables were daily measures of clinically relevant behavioral excesses (CRB-E) and daily participant-rated EA, respectively. Additionally, we collected weekly measures of EA, along with pre-, mid-, post-treatment, and 3-month follow-up clinical outcome measures. Overall, synchrony across daily, weekly, and pre/post nomothetic measures was largely observed across participants, and findings suggested improvement in clinical outcomes for two of three participants. Daily measurements of CRB-E and EA fluctuated considerably within both baseline and intervention phases. Cross-lagged correlation analyses revealed no evidence of temporal precedence of change in daily measured EA over change in daily measured CRB-E (or vice versa). Implications of these findings and directions for future research are discussed. © The Author(s) 2025.