How intellectual disability may bias psychologists' clinical impressions: An examination of diagnostic overshadowing

The term "diagnostic overshadowing" was coined in 1982 (Reiss et al., 1982) to refer to a phenomenon in which a diagnosis of intellectual disability (ID) is so salient that it "overshadows" the presence of other mental health conditions, whose symptoms are falsely attributed to the ID. Much of the research on this topic was conducted more than 20 years ago using a singular methodology. The present study aimed to update the research on diagnostic overshadowing and address methodological concerns with previous studies. Three hundred eighteen licensed psychologists participated in an online survey in which they viewed information about a simulated client and answered both open-ended and Likert-type questions about their diagnostic impressions. Participants were randomly assigned to view background information that suggested the client either did or did not have ID, and they either read a text vignette describing schizophrenia symptoms or watched a video vignette of a mock clinical interview. On the Likert-type items, schizophrenia was rated as significantly less likely in the ID condition compared to the non-ID condition. However, the magnitude of this difference was small. Open-ended questions did not reveal evidence of diagnostic overshadowing, as 96% of participants in the ID condition considered a mental health diagnosis in their response. Watching the video vignette had no effect on diagnostic impressions. Results suggest that psychologists do recognize the presence of a mental health condition in a person with ID, but there may be some reduced accuracy in the specific diagnosis that is made. (PsycInfo Database Record (c) 2025 APA, all rights reserved).