How Do Children with ADHD and Autism Differ in Their Development?

What you need to know

• Children with ADHD and autism show more developmental differences compared to their peers, but these differences are often subtle.
• No single developmental sign or group of signs can reliably predict ADHD or autism in adolescence.
• Developmental differences are common in all children, not just those with ADHD or autism.

Background on ADHD and Autism

Attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) are conditions that affect how the brain develops and functions. ADHD is characterized by difficulties with attention, hyperactivity, and impulsivity. It affects about 5-15% of children and teens. Autism involves challenges with social communication and interaction, as well as restricted or repetitive behaviors and interests. It affects approximately 1-4% of children and teens.

Both conditions often start early in life, but their exact causes are unknown. Researchers believe that a combination of genetic and environmental factors play a role. Many children have symptoms of both ADHD and autism - about 1 in 8 children with ADHD also meet criteria for autism, and 40-70% of youth with autism have significant ADHD symptoms.

How the Study Was Conducted

This study aimed to better understand how children with ADHD and autism differ in their development compared to other children. The researchers analyzed data from 3,623 children who were followed from birth to age 15 as part of a large study called the Fragile Families and Child Wellbeing Study.

The study collected a wide range of information about the children’s development, including:

• Physical health and growth
• Family history
• Psychological and social development
• Educational progress
• Behavior at home and school

In total, over 500 different factors were examined. The researchers compared children who were diagnosed with ADHD or autism by age 15 to those without these diagnoses.

Key Findings

Broad Developmental Differences

The study found that children who were later diagnosed with ADHD or autism showed differences across many areas of development compared to their peers. Some key findings include:

• Children with ADHD differed significantly on 52% of the factors examined
• Children with autism differed significantly on 38% of factors
• All differences indicated more challenges or difficulties for the ADHD and autism groups

However, the overall pattern of development was similar across groups. Areas that were challenging for children with ADHD or autism were also relatively challenging for other children, just to a lesser degree.

Most Indicative Signs

For ADHD, the most indicative signs were closely related to the core symptoms of the disorder:

• Difficulties with attention
• Hyperactivity
• Impulsivity
• Problems with anger
• Anxiety in social situations

For autism, a broader range of factors were most indicative:

• Speech problems
• Limited interests
• Lack of self-confidence
• Difficulty making friends
• Arguing with others
• Not helping with chores at home

Interestingly, only two factors - being male and having speech problems at age 9 - were strongly indicative for both ADHD and autism.

Predictive Accuracy

The researchers used the most indicative developmental signs to see how accurately they could predict which children would be diagnosed with ADHD or autism by adolescence. The results showed:

For ADHD:

• 66% of adolescents with ADHD were correctly identified
• But 62% of those identified as likely having ADHD did not actually have it (false positives)

For autism:

• 82% of adolescents with autism were correctly identified
• But 88% of those identified as likely having autism did not actually have it (false positives)

This suggests that while developmental differences exist, they are not specific or consistent enough to reliably predict these conditions.

Prevalence of Developmental Differences

An important finding was that developmental differences were common in all children, not just those with ADHD or autism:

• Children with ADHD showed differences on 18.7% of developmental factors on average
• Children with autism showed differences on 20.0% of factors
• Children without either condition still showed differences on 15.6% of factors

In fact, 89% of children without ADHD or autism showed differences on at least 10% of the developmental factors examined. This highlights that some degree of developmental variation is normal and expected.

Why Developmental Signs May Not Predict ADHD and Autism

The researchers proposed several reasons why developmental differences were not more predictive of later ADHD and autism diagnoses:

1. Symptoms exist on a spectrum: The traits associated with ADHD and autism may exist to varying degrees in all people, rather than being distinctly present or absent.

2. Symptoms fluctuate over time: The core characteristics of ADHD and autism may change considerably as children grow and develop.

3. Conditions are heterogeneous: There may be many different developmental pathways that can lead to ADHD or autism, rather than one clear pattern.

4. Normal developmental variation: As shown in this study, some degree of developmental difference is common in all children.

Implications

This study has important implications for how we think about and assess ADHD and autism:

1. Developmental history alone is not enough: While understanding a child’s developmental history is important, it should not be the sole or primary basis for diagnosing ADHD or autism. A comprehensive evaluation of current symptoms and functioning is crucial.

2. Avoid over-interpretation: Parents and clinicians should be cautious about over-interpreting normal developmental variations as signs of ADHD or autism. Some degree of difference is expected in all children.

3. Consider multiple factors: The development of children with ADHD and autism differs across many areas, not just core symptoms. A holistic view of the child is important.

4. Recognize change over time: ADHD and autism symptoms may fluctuate considerably as children grow. Ongoing monitoring and reassessment may be needed.

5. Individualized approach: Given the heterogeneity in how ADHD and autism manifest, assessment and treatment should be tailored to each child’s unique profile of strengths and challenges.

Conclusions

• Children with ADHD and autism show more developmental differences compared to peers, but these differences are often subtle and not specific to the conditions.
• No single developmental sign or pattern can reliably predict later ADHD or autism diagnoses.
• Some degree of developmental variation is normal and common in all children.
• Assessment of ADHD and autism should consider current symptoms and functioning in addition to developmental history.