Lead author and University of Otago paediatrics and child health senior research fellow Dr Nick Bowden said while the relative risk was high, it was important to remember that deaths in this group remained rare, and the vast majority would lead long and healthy lives.
However, young people with neurodevelopmental conditions faced substantial and preventable health inequalities, and the greater mortality risk highlighted urgent need for intervention, he said.
The research project brought together a multidisciplinary team from universities and research organisations across the country, including leadership from disability researchers with neurodevelopmental conditions to ensure lived experience was embedded in the research.
"This study provides an important foundation for shaping policies, services, and community actions that ensure all children and young people, regardless of neurodevelopmental condition, can live long, healthy, and fulfilling lives," Dr Bowden said.
"What these findings highlight is the urgent need for targeted healthcare interventions, improved access to medical and mental health services, and systemic changes to address the social and structural barriers which contribute to health inequities."
The study analysed the mortality risk among all people born in New Zealand between 1995 and 2009.
About 40,000 of them (4.5%) had a neurodevelopmental condition, identified via hospital records, specialist mental health services, disability support databases, or through prescriptions.
Six main groups were studied — ADHD, autism, intellectual disability, specific learning and motor disorders, communication and language disorders and foetal alcohol spectrum disorder.
Recorded deaths were grouped into three categories — medical causes (such as infections or chronic diseases), injuries (including accidents), and suicide.
Those with neurodevelopmental conditions were five times more likely to die before age 25.
The study also found females were almost 10 times more likely to die than females without neurodevelopmental conditions, he said.
"Risk also varied greatly by condition. Those with specific learning and motor disorders had 8.5 times higher mortality; intellectual disability was 8 times higher; communication and language disorders was 6 times higher; autism was 2.5 times higher; and ADHD was about 2 times higher."
Dr Bowden said the causes of death also differed.
Youth with any neurodevelopmental condition were 12 times more likely to die from medical causes, while injury-related deaths and suicide were almost twice as high.
Co-author and Otago paediatrics and child health autistic researcher Joanne Dacombe said the findings called for better, targeted wellbeing, mental health, and crisis-support services, stronger suicide-prevention initiatives, and greater focus on environmental safety across all facets of life for young people with neurodevelopmental conditions.
That included early identification and intervention, especially in early childhood; integrated, multidisciplinary care across health, education, and disability services; equitable access to health and mental health support, particularly for groups facing structural barriers; training for clinicians and educators to improve awareness of neurodevelopmental conditions and reduce diagnostic overshadowing; and community-led and culturally grounded approaches that recognise neurodiversity as part of human diversity.
