How is ADHD diagnosed?

By Dr Andrea McGladeGeneral20 Jul 2018

ADHD Diagnosis

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most common reasons for referral to a paediatrician. Sometimes parents are worried, sometimes school has asked to have a child checked for ADHD, and sometimes it’s even the opposite – parents seeking reassurance that their child doesn’t have ADHD.

The trouble with diagnosing ADHD is that like ASD there’s no single test, such as a blood test or genetic test, that can diagnose it. Instead it’s usually whether a child fulfills enough criteria on a checklist and it causes difficulties in functioning in day-to-day life. This is a pretty simplistic way of thinking about one of the most complex functions of our brains – our executive functions. I think it’s important to understand the role of our executive functions and what difficulties they may be causing specifically for your child, rather than just using a simple checklist.

So what are executive functions and why are they so important?

There are a several key tasks that our executive functions control:

Attention control:

  • particularly sustained attention for more difficult tasks; the more difficult the task the shorter the attention span, and the easier the task (i.e. X-box!) the longer the attention span. So, for example, if your child has dyslexia (difficulty reading) then when doing reading or spelling-related tasks they will have the shortest attention span.
  • attentional shift; when children get distracted, instead of being able to shift their attention back, they continue to shift off task. When they are deeply engaged in a task it can be hard to shift off that task; there is ‘sticky’ attention or attentional rigidity. This is often behind difficulty making transitions from one task to another. Attentional rigidity means they often get ‘stuck’ on a thought or idea and can’t let go and move on.

Working memory:

  • our working memory helps us hold information in our mind long enough to be able to use that information, or process or manipulate that information. An example is doing mental arithmetic; imagine calculating 14 x 17 in your mind….you have to hold initially two ‘bits’ or pieces of information (14 and 17) and then start the calculations (7 x 4 = 28), which is now at least three bits of information. Then (1 x 7) + 2 = 9, which is at least four to six bits of information (phew!)… and so it quickly adds up and we’re only halfway there!
  • we can only hold a finite amount of information in our working memory. If you have a small working memory capacity then you can only hold a small amount (say two to four ‘bits’) of information in your working memory and manipulate that information. If you try to add more ‘bits’ in then rather than still working at capacity – three or four or five bits – then usually everything gets lost except the first or last information that went into your ‘memory trace’.
  • adequate working memory is critical for school and academic learning across the curriculum; in reading, mathematics and producing written work.

Sequencing and planning:

  • this is one of the most critical cognitive skills in terms of impact on daily living. Our ability to sequence and plan is essential to organising our thoughts and making a step-wise plan; ‘I need to do this, then this, then this….’ etc. It impacts on children’s ability to be able to follow multi-step instructions, to be able make decisions (thinking through ‘If I make this choice then this is what happens, or if I make this choice then this is the alternative’) or carry out tasks that actually involve breaking down the job into smaller tasks (like ‘clean up your toys/room’).
  • difficulties in sequencing and planning often cause difficulties in organising ourselves and carrying out activities of daily living – like getting meals, packing bags for school, remembering where we put things and not losing our belongings.
  • is often behind ‘Oppositional Defiant Disorder (ODD)’ or more recently ‘Persistent Demand Avoidance (PDA)’ – children are given an instruction that is actually quite complex and needs to be mentally broken down into smaller pieces, which causes them to get stressed. When they get a wave of stress, they go into fight/flight/freeze mode and families and others see the anger or defiance or avoidant behaviour. I don’t find these diagnostic labels helpful as they don’t help explain why a child is struggling in this way.

Impulse control:

  • our executive function is our ‘stop and think’ mechanism; it acts like a filter, to filter out random or unhelpful thoughts that wander through our mind from time to time but we know we don’t (or shouldn’t) act on. A very famous example is the marshmallow test (now see Dr Google!).
  • children with poor impulse control often struggle to understand why they do things too. If you ask them why they did such a silly thing, they’ll often reply ‘I don’t know’ – and they don’t. There’s been no thought involved whatsoever, just straight from impulse to action with no thinking in between. It is usually every bit as confusing for the child as it is for you.

Degrees of difficulty

Some children have problems with their executive function from time to time and only when they need it most (their sustained attention for difficulty tasks) – such as when reading or writing. There are other children who have problems all the time.

Physical, emotional and cognitive stressors can impact a child’s executive function. Other known factors that can cause difficulties include poor sleep, motor coordination difficulties, sensory issues, anxiety, trauma, foetal exposure to alcohol, premature birth and low birth weight.

When I am assessing a child for ADHD, I look for those signs of poor executive function and I consider the stressors the child may be facing. This information helps to know what issues need to be addressed. We don’t necessarily need to use a diagnostic label of ADHD if it’s not helpful, especially if instead we decide to use the description of ‘poor executive function’ rather than a label. It also means there are lots of different ways we can support your child’s developing executive function skills without necessarily having to use medication. And once those adults around your child understand that with poor executive function it’s a case of ‘can’t do’ rather than ‘won’t do’, there will also be a more supportive environment for your child.

This post was written by Specialist Developmental Paediatrician Dr Andrea McGlade.


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