Around 3% of children suffer from symptoms of both autism and ADHD

A study in Spain found that around 3% of schoolchildren exhibit symptoms of both autism and attention-deficit/hyperactivity disorder (ADHD). Approximately 0.5% of children could be diagnosed with both disorders. About 33% of autistic children and 31% of those with autism symptoms that do not reach the diagnostic threshold also had ADHD. Additionally, 10% of children with ADHD also had autism. The paper was published in Autism Research.

Autism, or autism spectrum disorder (ASD), is a developmental condition characterized by challenges with social interaction, communication, and repetitive behaviors. It affects individuals differently, ranging from mild to severe, with some people displaying significant intellectual disabilities, while others may have average or above-average intelligence. Early signs of autism typically appear in childhood, often before age three, and can include delayed speech, difficulty understanding social cues, and a preference for routine.

Another mental health disorder often diagnosed in childhood is attention-deficit/hyperactivity disorder (ADHD). ADHD is a neurodevelopmental condition characterized by persistent patterns of inattention, hyperactivity, and impulsivity that interfere with daily functioning. Individuals with ADHD may struggle to focus, organize tasks, sit still, or control impulses, which can affect their performance at school, work, and in social situations. ADHD can persist into adulthood, often requiring ongoing management.

Study author Josefa Canals and her colleagues aimed to explore how often ADHD and autism co-occur in the same children. The study was part of the Neurodevelopmental Disorders Epidemiological Research Project, conducted between 2014 and 2019 in the province of Tarragona, Spain.

The study participants included 3,374 preschoolers (4–5 years old) and 3,520 school-aged children (10–11 years old). Over 99% of the teachers of these children participated in the study, but only 54% of the families did, resulting in a final sample of 3,727 children with information from both families and teachers. The study authors determined the likelihood of autism and ADHD based on information obtained from both parents and teachers.

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The results showed that around 3% of children had symptoms of both autism and ADHD. The co-occurrence of autism and ADHD was much higher in boys than in girls—4–5% vs. 1–2%, depending on whether the diagnosis was based on information from parents or teachers. The study authors estimated that around 0.5% of children could be formally diagnosed with both disorders.

Thirty-three percent of children with autism also had ADHD, with the rate being higher among older children (46%) compared to younger ones (22%). Ten percent of children with ADHD also had autism, with the percentage being somewhat higher among younger children (16%) than older children (8%). However, it remains unclear if this difference is due to random variation. An additional 6% of children with autism showed symptoms of ADHD that did not reach the diagnostic threshold.

“Autism and attention deficit hyperactivity disorder (ADHD) frequently coexist, but prevalence reports exhibit significant variability based on population characteristics and assessment methods. In the present study, parents and teachers reported a similar 3% prevalence of autism and ADHD traits, with an estimated comorbid diagnosis prevalence of 0.5%. Only 16% of the children had received prior diagnoses for both conditions, although parents and teachers identified traits of autism and ADHD in almost all cases. Based on the findings, early screening for co-occurring autism and ADHD in both school and family settings is recommended,” the study authors concluded.

The study sheds light on the prevalence of ADHD and autism among children in Spain. However, it should be noted that this study only involved children from one province in Spain, and the reported percentages might not be the same in other parts of the world.

The paper, “Prevalence of comorbidity of autism and ADHD and associated characteristics in school population: EPINED study,” was authored by Josefa Canals, Paula Morales-Hidalgo, Núria Voltas, and Carmen Hernandez-Martínez.