Waiting Times and Influencing Factors in Children and Adults Undergoing Assessment for Autism, ADHD, and Other Neurodevelopmental Differences

This study explored waiting times and the factors influencing them in child and adult populations undergoing assessment for autism, ADHD, and other neurodevelopmental differences. The analysis focused on a retrospective review of 408 cases with assessments completed between October 2021 and May 2022, conducted by 30 diagnosing teams in Scotland. Data included age, final diagnosis, demographics, medical and developmental history, contact frequency, and assessment service adherence to best-practice standards. Waiting times were calculated, and relationships were analyzed using linear regression. Median waiting times were 525 days (IQR 329–857) for children/adolescents and 252 days (IQR 106–611) for adults. Only 20% of children's and 47% of adult assessments met the proposed 252-day diagnostic time target. Autism and ADHD were the most common diagnoses. Receiving > 1 neurodevelopmental diagnosis on completion was uncommon. Demographic factors did not significantly affect waiting times. Children/adolescents with more complex developmental and medical histories experienced longer waits (100.3 weeks vs. 67.7 weeks; p < 0.001), while adults with similar histories had shorter waits (32.7 weeks vs. 57.4 weeks; p = 0.016). Adults with ADHD experienced longer waits than autistic adults (63.4 weeks vs. 38.6 weeks, p = 0.002). Adherence to best-practice quality standards was associated with shorter waits for children (β = 0.27, p = 0.002), but the relationship between standard adherence at different stages and for adults was less clear. More frequent appointments correlated with shorter adult waits (33.7 weeks vs. 59.2 weeks, p = 0.015). Gender distribution was balanced among adults, but children's services included more boys. The study highlights long waits and the need for improvement in processes.