A Systematic Quality Review of Single-Case Experimental Designs Using Acceptance and Commitment Therapy in Adult Clinical Populations

Recent publications within Contextual Behavioral Science provided a rationale for the expansion of intervention efficacy research using methods that capture idiographic factors and processes. We conducted a systematic review of the use and quality of single-case experimental designs (SCED) within the Acceptance and Commitment Therapy (ACT) literature in adult clinical populations. The systematic review was conducted according to PRISMA guidelines and the databases CINAHL, MEDLINE, PsycINFO, PsycArticles and OpenGrey were searched for peer-reviewed articles. Further studies were sought through review of reference lists of all full text studies. Studies were assessed against What Works Clearinghouse (WWC) single-case design standards. Twenty-six studies met eligibility criteria and were conducted within research teams all implementing multiple-baseline designs. Twenty-four studies did not meet WWC standards with most failing to ensure a degree of concurrence across participants. The extent of randomisation methods was also captured. The review highlights the sparsity of SCEDs within ACT literature in clinical populations and current methodological practices. Limitations of the review and implications for future research are discussed.