Internet-based acceptance and commitment therapy for bipolar disorder: A randomized controlled pilot trial.

Internet-based Acceptance and Commitment Therapy (iACT) offers a promising, scalable intervention format for individuals with bipolar disorder (BD), yet its feasibility and preliminary efficacy remain underexplored. This pilot randomized controlled trial evaluated the acceptability, feasibility, and initial efficacy of a 7-day self-guided iACT program delivered via a secure, mobile-responsive platform. Seventy individuals were screened, of whom 60 clinically stable adults with BD (aged 18-60) met eligibility criteria and were randomized to either the iACT group (n = 30) or an active control group receiving digital psychoeducation (n = 30), yielding a recruitment rate of 85.7 %. Retention at post-intervention was 100 %. In the iACT group, 93.3 % (28/30) met predefined adherence criteria (completion of ≥5 modules), indicating high intervention engagement. Between-group comparisons using ANCOVA (controlling for baseline scores) showed that the iACT group demonstrated significantly greater improvements in psychological flexibility (AAQ-II), reduced cognitive fusion (CFQ), improved social functioning (SDSS), and lower manic symptoms (YMRS), with small-to-medium effect sizes (Cohen's d = -0.28 to -0.59). Differences in depression symptoms (SDS) approached statistical significance (p = .054). High recruitment, retention, and adherence support the feasibility of brief iACT for BD. Preliminary efficacy signals justify a definitive RCT to evaluate clinical effectiveness.