Attention Deficit Hyperactivity Disorder (ADHD)

Attention deficit hyperactivity disorder (ADHD) is a neuro-developmental disorder characterised by persistent patterns of inattention and/or hyperactivity-impulsivity.

We mentioned ”inattention“ as well as “impulsivity-hyperactivity” above - let’s define these terms:

• Inattention - difficulty remaining focused and organised. It can be seen by lacking persistence, wandering off task, not remaining focused on the task at hand.
• Impulsivity - hasty actions without forethought that may present harm to the individual. It can be seen as social intrusiveness or making important decisions without thinking clearly about them.
• Hyperactivity - excessive motor activity and fidgeting in children. Adults may be restless and wear others out with their activity.

Pathophysiology

We are not too certain of what actually occurs in ADHD. The current perspective is that it is a combination of genetic and environmental factors leading to changes to brain neurochemistry,structure and function.

1. Genetic factors - evidence shows that there is a genetic component associated with ADHD. Some hypothesise that it is the outcome of the interaction of multiple genes while others believe it is the phenotypic expression of multiple allele variants.
2. Environmental factors - strong risk factors associated with ADHD are maternal smoking during pregnancy and low birth weight. Preterm delivery, epilepsy, acquired brain injury, lead exposure, iron deficiency, alcohol exposure during pregnancy, psychosocial adversity and adverse maternal mental health are other factors that may be associated with the disease too.

It is believed that structural and functional changes in the brain occur as well as changes to the levels of neurotransmitters in the CNS. Stimulants increase the free brain levels of noradrenaline and dopamine by preventing presynaptic neuronal reuptake which then triggers the release of these neurotransmitters. This suggests that ADHD may occur due to dysfunction of noradrenaline and dopamine. This is why we can treat ADHD patients with stimulants even though it would be easy to think that they require depressants.

Structural changes are shown when using neuro-imaging to compare ADHD with normal controls. The findings are that there is a reduction in brain volume in certain areas of the brain in ADHD patients.

Functional changes show how there is increased connectivity in certain regions of the brain (such as ventral striatum and orbito frontal cortex) and lower connectivity in other regions of the brain (superior parietal cortex and precuneus networks).

🔢 Classification

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM-V), we can classify ADHD as:

• Predominantly inattentive presentation - if only inattentive criterion are met for at least 6 months. Makes up 20-30% of cases.
• Predominantly hyperactive-impulsive presentation - if only the hyperactive-impulsive criterion are met for at least 6 months. Makes up 15% of cases.
• Combined presentation - if both the inattention and hyperactive-impulsive criteria are met for at least 6 months. Makes up 50-75% of cases.

Patients can be classified as being in partial remission if full criteria were previously met but are not met anymore but symptoms still affect aspects of their life. 65% of children go through partial remission. Only 15% carry the diagnosis into adulthood.

🔍 Investigations

Although we described the differences seen in brain structure with neuroimaging, there is currently no formal imaging study or laboratory study to confirm the diagnosis.

When suspecting ADHD, we can do the following:

• Conner’s questionnaire and other questionnaires - these are often done by the parent to gather information and suggest the diagnosis of ADHD.
• School observation and school reports - these are useful to observe the child’s functioning and interactions in the classroom. The school report may suggest issues relating to their academic attainment. It is important to identify the problem persisting in more than one setting.
• Qb test - the Qb test is a diagnostic screening tool that uses the child’s age and gender to provide matched comparisons to assess the child’s ability to concentrate, their movement and their impulsivity. It is more objective as it provides comparisons. The child sits in front of a computer screen with a headband on. The headband has a reflective ball on it which is picked up by a tracking camera to assess movement. The child responds to certain shapes seen on the computer.

🧰 Management

For patients with suspected ADHD we should:

1. Assess the social and educational impact of their symptoms.
2. We can implement a period of watchful waiting for up to 10 weeks.
3. Self-help and simple behavioural management should be encouraged.

If symptoms are severe the child would need a referral to Child and Adolescent Mental Health Service (CAMHS) for appropriate assessment and management .