Autism and Attention Defecit Hyperactivity Disorder

Autism and Attention Defecit Hyperactivity Disorder

by Dr Avril Brereton

Autism and Attention Deficit Hyperactivity Disorder (ADHD) are the two main classes of neurodevelopmental disorders which begin in early childhood.  Symptoms of attention deficit and hyperactivity are a common problem in children with autism. The problem of excessive hyperactive, inattentive and impulsive behaviour in children is not new and has been described in medical literature from the 19th century. 

What causes ADHD?

Current theories include an interaction of:

  • genetic predisposition
  • central nervous system dysfunction resulting from pre and early postnatal traumatic or toxic events and
  • environmental and social influences. 

How is ADHD diagnosed?

The diagnosis is based on a clinical judgement that there are sufficient symptoms of inattention and hyperactivity/impulsivity together with the decision that these symptoms cause significant impairment in daily functioning in at least 2 settings and are not consistent with the developmental level of the child.  The diagnosis requires a careful and comprehensive history of the child's development and behaviour from the parents and other informants such as the teacher, together with observation of the child in both structured and unstructured activity.  A structured cognitive assessment, apart from providing information on specific learning difficulties and related problems such as deficits in short term auditory memory, will also reveal problems with concentration and distractibility.

What are the symptoms?

Apart from high levels of distractibility and inattention, children with ADHD:

  • are disorganised and are usually unable to follow routine and complete tasks
  • have difficulty monitoring their behaviour and therefore often interrupt others
  • have difficulty following rules
  • have inappropriate and impulsive behaviour.

Those who also suffer from hyperactivity:

  • are constantly restless and fidgety
  • have difficulty remaining seated
  • behave as if they are driven by a motor.

These behaviours are influenced by the environment and the degree of external stimulation and sensory complexity.  Therefore, observers may report differences in behaviour depending upon the context.  For example a teacher in a busy noisy classroom setting is more likely to observe inattention than a teacher's aide who has the child for individual teaching in a quiet library environment.  However, the symptoms and impairments are usually observed, at least to some extent, in all aspects of the child's daily life.

Associated problems

  • The primary symptoms of ADHD in children often lead to hostile interactions with other children who may reject them.
  • The majority of children with ADHD have various learning difficulties and relatively poor school performance in relation to their intellectual abilities.
  • Approximately 25% of individuals with ADHD have intellectual disability including delayed language development.
  • Children with ADHD have difficulty falling asleep, wake early and their sleep is often unsettled and complicated by breathing and snoring difficulties.

How does ADHD affect children with autism?

At least 13% of children with autism meet diagnostic criteria for ADHD. Symptoms of attention deficit and hyperactivity in children with autism impede and disrupt their learning, school adjustment and family life.  These symptoms of ADHD are responsive to educational, behavioural and pharmacological managements used for children with ADHD, although not always as successfully. 


A multimodal approach to management including:

  • medication,
  • special education,
  • behaviour modification and
  • parent education and skills training.

is likely to lead to the most enhanced treatment response.  Medication is the most important aspect of treatment, but multimodal treatments which consider the complex learning, behavioural and social problems of the child improves outcome. 

An elimination diet is effective for children where the specific provocative food such as tartrazine can be identified, but are of benefit to fewer children than medication.

Stimulant medications (methylphenidate and dexamphetamine) are the most frequently used medications.  Trials of the efficacy of stimulant medication clearly demonstrate immediate improvement in inattention, impulsivity and hyperactivity and a reduction in aggression.  The longer term effects on learning and academic achievement are less clear and there is a lack of good long term evidence of the effectiveness of stimulant medication.
B.J. Tonge, N. Rinehart, A. V. Brereton

Useful websites

National Institute of Mental Health

Mental Health Matters

Neuroscience for Kids