A new study published in the medical journal The Lancet Child & Adolescent Health is one of the most comprehensive to date examining the mental health of young people without intellectual disabilities aged 7 to 18 years in Iceland who are autistic, have ADHD or both.

The study is a nationwide, population-based cross-sectional and a collaborative project between Kristín Rós Sigurðardóttir, a psychologist at the Children's Mental Health Centre and Dagmar Kristín Hannesardóttir, an assistant professor at the Department of Psychology at the University of Iceland, Berglind Hauksdóttir, a psychologist at the Children and Family Clinic, Thomas Ollendick, a professor at Virginia Tech, Katrín Davíðsdóttir, a pediatrician at the Children's Mental Health Centre and Þórhildur Halldórsdóttir, an associate professor at the Department of Psychology at Reykjavík University. The study is based on data from over 2000 children and adolescents who were diagnosed with neurodevelopmental diversity through a central and standardized clinical diagnostic process at the Children’s Mental Health Center. There, a detailed assessment was carried out by experts in the assessment of neurodevelopmental diversity and psychiatric challenges, along with parent and teacher assessments of emotional and behavioral difficulties.

The main findings are that approximately 1.5% of children and adolescents without intellectual impairment aged 7-18 are autistic and 4.5% have ADHD. Of those who were autistic, about two out of three also had ADHD, which highlights how common it is that these neurodevelopmental diversities coexist – and how important it is to provide the group with appropriate support. Anxiety and eating disorders were more common among all neurodevelopmental diversity groups compared to children and adolescents without autism and ADHD. However, other mental health challenges, such as depression and obsessive-compulsive disorder (OCD), were similar in frequency across groups. The assessment of emotional and behavioral difficulties showed that emotional difficulties were more common among autistic children and adolescents (with or without ADHD), while behavioral difficulties were more common among those with ADHD, whether or not they were also autistic.

Why is this study important?

Most previous studies have been conducted among autistic children with and without intellectual impairment or have used imprecise diagnostic procedures. This study was the first to use a standardized, comprehensive diagnostic procedure in a national population-based sample, providing a clearer picture of the health needs of children and adolescents with a diagnosis of neurodevelopmental diversity without intellectual impairment.

The study also fills an important gap in previous knowledge. Until 2013, autism and ADHD could not be combined according to diagnostic systems, meaning that many children and adolescents with both manifestations may have been underdiagnosed or not receiving appropriate support. By examining both common and specific features of well-being in these groups, a foundation is laid that highlights the importance of individualized approaches in schools, health services, and community support.