Effectiveness of acceptance and commitment therapy for improving quality of life and mood in individuals with multiple sclerosis: A systematic review and meta-analysis

•ACT for distress in people with MS has variable findings.•ACT was found not to reduce anxiety or depression, or improve QoL, significantly.•Findings suggest ACT did not improve ACT-targeted processes.•A significant small effect of ACT on stress was found.•Small samples and wide confidence intervals make drawing conclusions challenging. To review the evidence for the effectiveness of Acceptance and Commitment Therapy (ACT) intervention on quality of life and mood, for individuals with Multiple Sclerosis (MS). A systematic search was conducted of PsycINFO, CINAHL, Embase, MEDLINE, Web of Science, Scopus and ContextualScience.org up to 13/01/2022. Grey literature was also searched via ProQuest Dissertations and Theses, and PROSPERO. We included Randomised Controlled Trials (RCTs) published in English, that examined the effectiveness of ACT for people with a diagnosis of MS. We were interested in outcomes of Quality of Life (QoL), mood (e.g., anxiety, depression and stress), and ACT-targeted processes. Methodological quality was assessed using the Cochrane Risk of Bias Tool v2. Where available, the extracted data were entered into a meta-analysis to determine weighted effect size estimates for the outcomes of interest. Six studies (191 participants), out of 142 identified, met inclusion criteria. Meta-analyses indicated a statistically significant small effect on stress (SMD = -0.49 [95% CI of -0.89 – -0.08]), in favour of ACT. There were no statistically significant effects of ACT on anxiety (SMD = -0.41 [95% CI of -0.93 – 0.11]), depression (SMD = -0.92 [95% CI of -1.91 – 0.06]), or ACT-targeted processes (SMD = -0.18 [95% CI of -0.62 – 0.25]). There was a small, nonsignificant effect on QoL, in favour of control conditions (SMD=0.39 [95% CI of -0.08 – 0.85]). Methodological quality of the studies was variable; all but one study had at least one high risk of bias. Findings suggest a small effect of ACT on reducing stress for people with MS, but not reducing anxiety or depression, or improving quality of life. Due to small sample sizes and few studies within this area, generalisability of findings is limited. Future trials should be pay more attention to methodological rigour.