Autism and ID dual diagnosis — assessment to behaviour and epilepsy (MEQ)

(i) Dual diagnosis and relative rule. Dual diagnosis means co-occurrence of ASD and intellectual disability as independent neurodevelopmental diagnoses. ID requires intellectual and adaptive deficits with developmental onset. ASD requires social-communication deficits plus RRBs with early onset and impairment. When ID is present, social communication must still be below that expected for the general developmental level to justify ASD — dual coding is allowed and preferred when both are present.^[1][2]

(ii) Assessment and AAC. Structure: developmental timeline; adaptive function; social communication relative to mental age; RRBs/sensory profile; multi-informant collateral; structured tools as aids (ADOS-2/ADI-R) with clinical judgment; psychology cognitive/adaptive testing. Communication: hearing history/review, speech-language pathology, total communication, and AAC now (not after years of waiting for speech). Genetic workup (microarray, fragile X) aligns with major ASD guidance after diagnosis.^[1][2]

(iii) Epilepsy interface. Epilepsy co-occurrence with autism is elevated and higher with co-occurring ID. Staring spells warrant seizure history, neurology liaison, and EEG when clinically indicated — do not assume all stereotypy is seizure and do not ignore true events. Medical screen for pain sources that drive behaviour change.^[3]

(iv) Challenging behaviour and non-drug care. Formulate: pain/medical, epilepsy, communication unmet need, sensory overload, environment/change, mental illness. First-line: safety, PBS/functional analysis, environmental and visual supports, AAC, parent/carer training (Bearss parent training evidence for disruptive behaviour in ASD), educational adaptations. Emerson epidemiology frames challenging behaviour as a common service-level problem needing systematic response.^[4][8]

(v) Irritability medicines and Tyrer. After formulation and non-drug optimisation, severe ongoing irritability may justify risperidone (RUPP: start low e.g. about 0.25–0.5 mg/day weight-based, slow titration, monitor weight/metabolic/EPS/prolactin) or aripiprazole (Owen: often 2 mg start, titrate; monitor metabolic effects and akathisia). Neither treats core social deficits. Tyrer 2008 found risperidone/haloperidol not superior to placebo for aggressive challenging behaviour in adults with ID — do not extrapolate paediatric ASD irritability evidence into uncritical lifelong antipsychotics for non-specific adult ID aggression.^[5][6][7]