Health Psychology, Vol 45(8), Aug 2026, 837-847; doi:10.1037/hea0001584
Objective: We modeled changes in both engagement versus nonengagement and frequency of engagement in moderate to vigorous physical activity (MVPA) in women with breast cancer (BC) participating in a trial of cognitive behavioral stress management (CBSM) intervention during the first year of treatment. Method: We recruited 240 women with Stage 0–III BC 2–8 weeks postsurgery and randomly assigned them to either a 10-week group CBSM intervention or 1-day psychoeducational (PE) control before they began adjuvant therapy. A brief version of the Seven-Day Physical Activity (PA) Report measured frequency of MVPA, and a measure of perceived stress management skills assessed stress awareness, relaxation skills, and coping confidence in participants at baseline (T1), 6 months (T2), and 12 months (T3) after randomization. We used a two-part latent growth to model change in both engagement versus nonengagement and frequency of engagement in MVPA. Results: The unconditional model showed significant changes in frequency of engagement in MVPA over time (β = 0.11, p p p = .02) compared with PE control, although CBSM did not affect MVPA frequency. Those in CBSM revealed greater increases in confidence in relaxation skills (p p > .05). Conclusions: CBSM increased the likelihood of MVPA engagement during primary treatment for BC. However, contrary to hypotheses, perceived stress management skills did not mediate this relationship. Further research should explore additional pathways to better understand how CBSM may have supported physical activity engagement during or after cancer treatment. (PsycInfo Database Record (c) 2026 APA, all rights reserved)