Psychiatric disorders in intellectual disability — dual diagnosis MEQ

(i) Diagnostic overshadowing. Bias in which a known ID diagnosis is so salient that clinicians attribute symptoms of mental or physical illness to the disability itself, delaying treatment. Staff saying "just his ID" is classic overshadowing. Mental ill-health is common (Cooper clinical prevalence ~40%). Overshadowing risks missed depression and missed medical illness.[1][3][4]

(ii) Modified presentation. In moderate ID, depression often presents as behavioural equivalents: increased self-injury, irritability, withdrawal from preferred activities, sleep/appetite change, tearfulness, skill regression — not necessarily articulate low mood or guilt. Compare against baseline; new change over weeks is decisive.[2]

(iii) DC-LD. Multi-axial Royal College system complementary to ICD for adults with learning disabilities; accommodates pathoplastic effects; hierarchical structure covering developmental disorders, psychiatric illness and problem behaviours. Use when standard ICD/DSM under-detect because of limited verbal report.[2]

(iv) Assessment and immediate plan. Timeline and collateral; physical exam with constipation/dental/pain screen; basic labs as indicated; medication review; adapted MSE and risk (self-injury, placement). Functional analysis of behaviour. Treat constipation and dental needs. Do not accept "just ID". Safeguarding review if neglect of health care. Capacity is decision-specific with support.[4]

(v) Psychotropics and adaptations. Long-term risperidone without diagnosis or review is inappropriate culture — Sheehan shows prescribing exceeds recorded mental illness; Tyrer shows antipsychotics not superior to placebo for aggression alone in many adults with ID. Deb guide: formulate, non-drug first for problem behaviour, clear targets, monitor, review. If depression confirmed, consider adapted psychological approaches where ability allows and/or antidepressant start low/go slow with monitoring; plan antipsychotic reduction if no ongoing psychotic indication, with metabolic/EPS monitoring during change. Multiagency behaviour support plan.[5][6][7][8]