Attention Deficit Hyperactive Disorder (ADHD)
Why is cognitive assessment important in ADHD?
What is ADHD?
Attention-Deficit Hyperactivity Disorder (ADHD) 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 neurodevelopmental 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 neurodevelopmental 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 ADHD 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 ADHD
Endpoints measured
Sustained attention
Working memory
Key research for CANTAB® in attention deficit disorders
The tests in this battery have detected cognitive impairment in ADHD across the age span with medium-large effect sizes, as well as detecting the effects of pharmacological interventions, for example methylphenidate and atomoxetine7.
The response inhibition test included in the battery, Stop Signal Task (SST), detects inferior frontal and anterior cingulate cortex hypoactivation in individuals with ADHD10; and drugs that show efficacy in the treatment of ADHD, such as atomoxetine, augment activation in right frontal cortical regions during this cognitive test11.
Research shows that cognitive impairment on the CANTAB® tasks significantly mediates the relationship between reduced white matter brain integrity and impaired school functioning in ADHD12.
Pathology and functional impact of ADHD
There is no singular ‘genetic cause’, but rather multiple genes are likely to confer risk or vulnerability towards developing the condition. Genes involved in the regulation of cognition and fronto-striatal brain circuitry, such as those relating to the dopamine and noradrenaline/norepinephrine neurochemical pathways are thought to be most involved4.
Current biological models for ADHD emphasise dysregulation of brain regions including the prefrontal cortex, anterior cingulate cortex, superior parietal cortex, caudate, and cerebellum5,6.
In terms of neurochemical involvement in ADHD, the dopamine and noradrenaline/norepinephrine systems have been particularly implicated, not only as a consequence of gene studies but also in terms of why certain treatments are effective but others are not8,9.
