Diagnostic overshadowing reviewed and reconsidered.

Diagnostic overshadowing is a robust bias negatively affecting the accuracy of clinicians' judgments about concomitant mental illness in persons with mental retardation and mental illness. Reviewing 12 studies, we examined moderators of diagnostic overshadowing. Most client and clinician-based demographic variables have had limited usefulness. However, clinicians' cognitive complexity has been found to negatively affect overshadowing. Causal mechanisms of overshadowing remain largely unexplored, and diagnostic overshadowing has yet to be empirically demonstrated outside a single methodological approach. Areas needing further research are discussed and the recommendation made that researchers (a) better specify clinical decisions composing overshadowing, (b) attend to the type of processes by which diagnostic overshadowing occurs, (c) increase appreciation of environmental or situational variables related to overshadowing, and (d) engage in more comprehensive exploration of overshadowing using qualitative and other diverse methodologies.