Autism spectrum disorder

Why is cognitive assessment important in autism?

Why is it important to do research in autism?

Individuals with autism spectrum disorder often exhibit cognitive deficits that reflect underlying abnormalities in brain structure and function5,6. Our recommended test battery for research of autism spectrum disorder’s assesses the core domains impaired in ASD, as well as those likely to be affected by novel interventions.  

The search is on for treatments that can ameliorate the core symptoms of ASD, and cognitive impairment, in order to maximise long-term outcomes and quality of life for affected individuals. 

What is autism?

Autism is a neurodevelopmental disorder associated with problems with social communication and/or interaction, and occurrences of restricted or repetitive patterns of behaviour, interests, or activities. 

Autism was previously distinguished from Asperger’s syndrome, but the latest version of the Diagnostic and Statistical Manual (DSM-5) instead uses a broader ‘umbrella’ category of Autism Spectrum Disorder (ASD). 

The condition affects approximately 1 in every 100 children. It is not fully known what causes autism but it is thought to include a mixture of environmental and genetic factors1. 

The UK National Institute for Health and Care Excellence (NICE) has a number of guidelines regarding the recognition, diagnosis, and treatment of autism2-4. Generally speaking, people with autism should be supported via a multidisciplinary approach, by people with expertise in the disorder. This can involve support from clinical psychologists, nurses, occupational therapists, psychiatrists, social workers, speech and language therapists, and other support staff. 

What is ADHD?

Attention-Deficit Hyperactivity Disorder (ADHD), otherwise known as hyperkinetic disorder, is a condition that affects people’s behaviour. ADHD can cause restlessness, trouble concentrating and impulsive behaviour1. For example, children with ADHD may blurt out answers in the classroom, fidget and find it impossible to keep still and struggle to focus on what a person is saying. 

ADHD is the most common psychiatric disorder of childhood, affecting at least 5% of children globally. Symptoms persist into adulthood in up to 60% of childhood cases2. 

For a diagnosis of ADHD to be given, the symptoms must be functionally impairing and occur in at least two distinct settings, for example at home and at school. 

Considerable research has examined the long-term consequences of ADHD, highlighting its global importance for society. In a systematic review of the data, untreated ADHD was associated with poorer long-term outcomes across all categories considered: these included academic performance, job performance and employment status, self-esteem, quality of life, and risk of driving accidents3. 

ADHD is a treatable psychiatric disorder, with medium to large effect sizes in terms of symptomatic improvement, versus control conditions, over the short-medium term4

ADHD is often misdiagnosed, and is frequently comorbid with other mental (and physical health) disorders. First-line treatment options for ADHD can include consideration of psychotherapy and/or medication, but these should always be offered as part of a comprehensive package of care. The most appropriate treatment options and sequencing of treatment options can vary considerably depending on factors such as the age of the individual, severity of disease, and patient/family preference. 

Why it is important to do research in ADHD?

The core symptoms of attention deficit disorders are cognitive in nature (inattention, hyperactivity, and/or impulsivity). These cognitive deficits often reflect underlying brain circuitry dysfunction (including prefrontal regions) and of neurochemical transmission, including the dopamine and noradrenaline/norepinephrine pathways5-9. Our recommended test battery for attention deficit disorders assesses the cognitive domains most likely to be impaired, as well as those likely to be affected by interventions. 

Recommended CANTAB test battery for autism

The tests in this battery are sensitive to cognitive dysfunction across the spread of disorder severities and across age ranges (childhood, adolescent, and adult ASD)7-10. 

Endpoints measured

Executive function

Episodic memory

Planning

Processing speed

Key research for CANTAB® in autism spectrum disorders

These tests have been shown to discriminate neuropsychological differences between ASD and other common comorbid conditions, such as Attention-Deficit Hyperactivity Disorder (ADHD) and depression11. 

Research has demonstrated that the Spatial Working Memory (SWM) test is highly sensitive to cognitive dysfunction in autism, highlighting that deficits in this cognitive process are prevalent within individuals with autism5. 

Steel et al, (2007)12 

Pathology and functional impact of autism spectrum disorders

As with most psychiatric disorders, the causes and brain basis of ASD is not fully understood. Genetic factors are important, with heritability estimates for ASD being 77-99%, higher than for many other prevalent neurodevelopmental disorders13

Environmental factors also play a role in the aetiology of ASD. For example, premature birth and maternal diabetes have been associated with elevated risk of offspring developing ASD14,15 though the causal pathways are unclear. Abnormalities of the cortex and cerebellum, which play key roles in cognition, are commonly reported in ASD compared to healthy controls16. 

Common findings include excessive brain volumes and other morphological abnormalities in frontal regions and in the amygdala; coupled with lack of sufficient connectivity between brain regions16

Other research into ASD suggests that there are underlying abnormalities in antioxidant capacity and immune function, including changes to immune cells in the central nervous system17. Consistent with underlying brain changes in ASD, studies report a range of cognitive deficits in such individuals18. 

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