LADDERS: A Proof-of-Concept Study of a Parent-Led Intervention for Anxiety in Autistic Children with Severe to Profound Intellectual Disability

Background: Anxiety is highly prevalent in autistic children with severe and profound intellectual disability (ID), yet few psychological interventions are tailored to the specific needs of this population. LADDERS is a manualised, parent-led graded exposure intervention developed to reduce anxiety-related avoidance in this underserved group. Methods: A proof-of-concept study was conducted using a single-case experimental design (SCED) with non-concurrent multiple baselines. Six families completed the 16-week LADDERS intervention, which was primarily delivered online by an Assistant Psychologist under clinical supervision. Primary outcomes were recorded through daily caregiver diaries. Secondary outcomes included behavioural observations, teacher ratings, standardised questionnaires, and qualitative interviews. Results: All participants completed the full intervention. Four of the six children showed reductions in daily-rated anxiety. Non-overlap of all pairs (NAP) analyses indicated moderate to large effects in the final intervention phase for most participants. Five children progressed through their graded exposure steps without significant increases in observed anxiety. Qualitative interviews highlighted improvements in child participation, parental confidence, and understanding of anxiety. No adverse events were reported. Conclusions: The LADDERS intervention was feasible to deliver and acceptable to families, with early signals of impact. These findings highlight the potential value of further investigation to explore the intervention’s impact and longer-term outcomes.