The current study examined the efficacy of an online Acceptance and Commitment Therapy (ACT) intervention at addressing chronic pain in individuals with Chiari Malformation (CM) with the hope of informing adjunctive treatment options.

52 adults (aged 18–65) with CM were randomized into either the treatment or a waitlist control group. Both groups completed baseline assessments followed by 8 weekly assessments of pain interference, anxiety, depression, sleep dysfunction, chronic pain acceptance, and psychological flexibility; the treatment group also completed 8 weekly online self-guided intervention modules. All participants were assessed at 8 weeks and 1-month post-intervention.

Using hierarchical linear modeling, significant group differences were identified in the trajectories of psychological flexibility and chronic pain acceptance such that the treatment group improved at a faster rate. The curve in the trajectory of sleep dysfunction differed between groups but outcomes did not differ. There were no significant group differences in pain interference, depression, or anxiety symptoms, and psychological flexibility did not mediate any of the significant findings.

ACT processes of change were effectively engaged, as demonstrated by significant improvements in psychological flexibility and chronic pain acceptance within the treatment group. Possible modifications to the intervention may be necessary to improve treatment of non-responsive symptoms.

Trial Registration. This study was registered with Clinical Trials.gov (Identifier NCT04089670, 19–17).