Co-occurring attention-deficit/hyperactivity disorder in children with autism in Singapore: patterns in diagnosis and management

Introduction This study aimed to describe the diagnostic and management profiles of children (including medication use) with co-occurrence of attention-deficit/hyperactivity disorder (ADHD) and autism (AuDHD) in a tertiary developmental service in Singapore.Methods This retrospective study reviewed children aged 0–16 years with AuDHD seen at a tertiary children’s hospital in Singapore between January 2018 and December 2023. Clinical and demographic data were extracted from electronic health records.Results Among 7859 autistic children under follow-up, 199 had AuDHD. Mean (SD) age at ASD and ADHD diagnosis was 4.7(2.3) and 7.4(2.0) years, respectively. Half of the children had predominantly hyperactive/impulsive ADHD. Mainstream education was attended by 63% of children, 79% had no documented adaptive difficulties and 10% had co-occurring mental health conditions. Non-pharmacological therapy was received by 89%, while 72% received ADHD medication. Almost all were started on methylphenidate (MPH), with 4% requiring transition to second-line non-stimulant medication. Conversion to long-acting MPH was more common after immediate-release than modified-release initiation (37% vs. 11%).Conclusion Higher rates of medication conversion for AuDHD children following immediate-release initiation suggest modified-release MPH may be preferable. The low observed co-occurrence rate suggests possible under-identification and highlights the need for more systematic screening for ADHD and mental health conditions in autistic children.