A multiple-baseline evaluation of acceptance and commitment therapy focused on repetitive negative thinking in panic disorder

Although cognitive-behavioral therapy (CBT) is efficacious for treating panic disorder, a segment of the population is not treated due to the treatment length and the acceptability of interoceptive exposure. This study explored the efficacy of a brief protocol based on acceptance and commitment therapy (ACT) focused on repetitive negative thinking (RNT) in adults suffering from panic disorder. We designed a 4-session RNT-focused ACT protocol because previous CBT studies considered this length “ultra-brief.” Additionally, although conducting exposure is consistent with the ACT model, we did not include explicit exposure exercises to increase the intervention acceptability. A randomized, multiple-baseline design across three participants was implemented with a 3-month follow-up. The effect of the intervention was evaluated through weekly scores on the Depression Anxiety and Stress Scale – 21 (DASS-21; S. H. Lovibond & P. F. Lovibond, 1995), Penn State Worry Questionnaire (PSWQ; Meyer et al., 1990), and the frequency of panic attacks. After the intervention, all participants ceased to experience panic attacks and showed clinically significant changes in the DASS-Total and PSWQ. The effect sizes comparable across designs were very large and statistically significant for the DASS-Total (d= 2.48), DASS-Depression (d= 1.45), DASS-Anxiety (d= 1.93), DASS-Stress (d= 1.63), and PSWQ (d= 2.36). All three participants also showed clinically significant changes and large effect sizes in experiential avoidance (d= 3.26), cognitive fusion (d= 3.58), and valued living (Progress: d= 0.72, Obstruction: d= 2.43). In conclusion, brief RNT-focused ACT interventions might be efficacious for treating panic disorder