Our study of 267,000 kids reveals the hidden burden of multiple developmental conditions

Our new study highlights a crucial, but often hidden, aspect of child health – the mental health impact of living with two or more neurodevelopmental conditions.

We found children with multiple neurodevelopmental conditions – such as attention-deficit hyperactivity disorder (ADHD), autism, learning difficulties, developmental delay, speech disorders, cerebral palsy, epilepsy, Tourette syndrome and behavioural problems – are much more likely to have depression and anxiety.

Our findings have important implications for health services and planning. They stress the importance of early and integrated care – where neurodevelopmental, educational and mental health services work together rather than separately.

We’re seeing more kids with multiple conditions

More children are being diagnosed with two or more neurodevelopmental conditions.

At the same time, mental health problems such as depression and anxiety are becoming more common in children and young people around the world. About 9% have a mental health disorder.

However, little was known about how often these emotional difficulties occur in children with multiple neurodevelopmental conditions, and whether the risk increases as the number of such conditions grows.

Understanding these patterns can help health professionals, schools and policymakers identify children most at risk and provide early, integrated support.

What we did

We analysed data from the National Survey of Children’s Health, a large, nationally representative survey in the United States. This survey collects information from parents or caregivers about their children’s physical and mental health, development, and family circumstances.

We combined data from 2016 to 2023, which included more than 267,000 children aged three to 17 years.

Parents were asked whether their child had ever been diagnosed with any of ten neurodevelopmental conditions.

We categorised children according to the number of neurodevelopmental conditions into five groups: no multiple neurodevelopmental conditions (none or one), two, three, four, and five or more neurodevelopmental conditions.

Parents also reported whether their child had ever been diagnosed with depression or anxiety, and if so, how severe these conditions were (mild, moderate or severe).

We then looked at how the number of neurodevelopmental conditions related to the likelihood of having depression or anxiety.

Our findings were clear and consistent

The more neurodevelopmental conditions a child had, the higher their risk of depression and anxiety.

Compared to children without multiple neurodevelopmental conditions, children with two of these conditions were about 4.7 times more likely to have depression and 5.8 times more likely to have anxiety.

Children with five or more neurodevelopmental conditions were more than 5.3 times more likely to have depression and 12.9 times more likely to have anxiety.

The severity of mental health problems also increased sharply. Children with multiple neurodevelopmental conditions were much more likely to experience severe depression or anxiety than mild forms.

This pattern remained after taking into account age, sex, race, country of birth, health service use, heart disease, diabetes, allergies, asthma, arthritis, body-mass index, physical exercise, adverse childhood experiences, family income, family structure, health insurance coverage and parental education.

How does this apply globally?

Health systems around the world face rising numbers of children with multiple neurodevelopmental conditions. So it is vital to understand these children are not a small minority – they represent a large and growing group who need thoughtful, coordinated care.

Although this study used US data, its findings have important lessons for countries around the world. This includes Australia, particularly as it grapples with reforming its National Disability Insurance Scheme.

Neurodevelopmental conditions are common globally. However, most Australian studies have focused on children with a single neurodevelopmental condition rather than those with multiple ones.

Very few Australian studies have examined what happens when a child has two or more neurodevelopmental conditions at the same time. And when they have, these often had small sample sizes.

What are the implications?

By showing the risk of depression and anxiety rises sharply as the number of neurodevelopmental conditions increases, our findings highlight an area that Australian research and policy could explore further.

With the growing number of children being diagnosed with neurodevelopmental conditions in Australia, understanding how these conditions interact and compound mental health risk is crucial.

Our work also suggests future Australian studies and child health programs should look beyond single conditions and consider the combined impact of multiple neurodevelopmental conditions on children’s emotional wellbeing, together with social and economic circumstances and the ability to access services.

Doing so could lead to better screening, earlier intervention and better coordination of care for children and families across both the health and education systems.

What now?

Based on our findings, several actions are needed at different levels:

1. Health-care professionals should routinely screen children with multiple neurodevelopmental conditions for anxiety and depression. Even if a child’s main diagnosis is neurodevelopmental, mental health needs should not be overlooked. Commonly, parents also need support.

2. Schools and teachers need training and resources to recognise emotional distress in students with neurodevelopmental challenges and to connect families with support services.

3. Parents and caregivers should be encouraged to discuss emotional wellbeing with health providers and seek help early if their child shows signs of worry, sadness or withdrawal.

4. Researchers should conduct long-term studies to explore why these conditions often occur together and which early interventions work best to prevent later mental health problems.

5. Policymakers should fund and strengthen integrated child neurodevelopment and mental health programs. For example, this could be school-based counselling; multidisciplinary care clinics that provide joint assessments by paediatricians, psychologists, and speech or occupational therapists; and family support networks offering parent training and peer-support groups.

Without early recognition, intervention and support, these children may experience ongoing difficulties in school, social isolation, and long-term mental health problems into adulthood.