FASD and Intellectual Disability Equivalence: A Meta-Analysis of Suggestibility During Forensic Interviews

Abstract

Intellectual disability (ID) equivalence describes conditions in which individuals function cognitively and adaptively at levels comparable to ID without meeting IQ-based diagnostic criteria. Fetal alcohol spectrum disorder (FASD) is characterised by impaired executive and adaptive functioning despite IQs often above the ID threshold, suggesting functional overlap with ID. This meta-analytic study is the first to examine whether FASD and ID share vulnerabilities in interrogative suggestibility. Two PRISMA-guided systematic searches of six databases were undertaken, and identified studies involving FASD or ID. Bayesian random-effects meta-analyses were conducted on Gudjonsson Suggestibility Scale–2 outcomes: Yield 1, Yield 2, Shift, and Total Suggestibility. Individuals with FASD showed levels of interrogative suggestibility comparable to, and sometimes exceeding, those with ID across all indices. Effect sizes were large for both groups, with particularly elevated Shift scores in individuals with FASD. Both groups are highly vulnerable to leading questions and interrogative pressure. Individuals with FASD may be especially prone to changing responses following negative feedback, highlighting important forensic interviewing implications.