Diagnostic Overshadowing of Psychological Disorders in People With Intellectual Disability: A Systematic Review.

Dell'Armo et al. (2024) hunted for every paper that tested diagnostic overshadowing in people with intellectual disability. They found 25 studies published between 1989 and 2022. Two raters scored each study for quality and counted how often doctors blamed the disability instead of naming a real mental-health condition.

One-third of the studies found no proof of overshadowing at all. The rest showed mixed or weak effects. Most studies were tiny, used different definitions, and lacked control groups. Overall, the team rated the evidence base as low quality and warned against assuming every psychiatric symptom in ID is automatically overshadowed.

Li et al. (2025) extends the warning into real-world prescribing. Their 2025 chart review of 269 Chinese inpatients with ASD shows kids who also have ID receive more antipsychotics and fewer antidepressants, a pattern the authors say may reflect overshadowing. Kristin’s review says the evidence for that bias is shaky, so the prescribing gap might be built on weak ground.

Pakenham et al. (2004) offers a concrete example. Their case series of 21 youth with ID and suspected early psychosis found most psychosis labels vanished after careful re-assessment. Kristin’s low-quality verdict supports this: without rigorous re-evaluation, clinicians risk both over- and under-diagnosis.

Horovitz et al. (2014) shows why accuracy matters. Adults with mild-moderate ID plus any Axis I disorder report sharply lower quality of life. If overshadowing leads you to miss treatable depression or anxiety, you leave real suffering unaddressed.

Don’t let the phrase “diagnostic overshadowing” shortcut your assessment. Use standard DSM criteria, add developmental context (A, 2005), and rule out sensory loss (S, 2001). When in doubt, collect data, consult a second clinician, and treat what you can treat. Accurate diagnosis protects quality of life and keeps your intervention plan honest.

Diagnostic overshadowing is a clinical bias in which symptoms of a psychological disorder are falsely attributed to a person's known intellectual disability.

The practical danger is that a treatable co-occurring condition, such as depression or anxiety, goes unrecognized because clinicians read the symptoms as just part of the disability.

The concept is central to dual-diagnosis assessment, where mental-health and developmental conditions must be evaluated as separate but interacting issues.

The review evaluated all available research, including dissertations and peer-reviewed articles, for a total of 25 studies.

Findings suggest overshadowing may be less ubiquitous than believed, with about one third of studies finding no overshadowing effect. Evidence quality was graded Low using the LEGEND tool, limited by outdated and analogue designs, small convenience samples, and weak statistics.

The balanced takeaway is to assess each disorder independently. Do not assume overshadowing in every case, but do guard against dismissing real psychiatric symptoms as features of intellectual disability.