If you spend any time reading about ADHD, you will probably come across a familiar explanation:
ADHD is an executive-function disorder.
It is an appealing idea, particularly because difficulties with planning, starting tasks, remembering things and controlling responses will sound very familiar to many people with ADHD.
But is it actually that simple?
A classic 2005 study by Willcutt and colleagues provides a much more interesting answer.
Published in Biological Psychiatry, the researchers conducted a meta-analysis bringing together 83 studies, involving 3,734 participants with ADHD and 2,969 without ADHD. Rather than looking at the results of a single experiment, they examined evidence across numerous studies of executive functioning.
What is executive function?
Executive functions are the mental processes involved in directing our behaviour towards a goal.
Think about knowing that you need to write an important report.
Knowing that the report exists isn't enough. You need to resist distractions, hold information in mind, decide where to start, organise the different steps and keep going until you've finished.
Those are the sorts of processes we are talking about when we discuss executive functioning.
So what did the researchers find?
There was strong evidence of a connection.
People with ADHD showed significant impairment across all the executive-function tasks examined. The strongest and most consistent differences involved response inhibition, vigilance, working memory and planning.
Interestingly, these differences were found in both clinic-referred and community samples, and the researchers reported that they weren't explained by differences in intelligence, academic achievement or symptoms of other disorders.
That seemingly supports the idea that ADHD is fundamentally an executive-function problem.
But there is an important but.
Executive dysfunction isn't the whole story
The effects were moderate, rather than universal.
Most importantly, the researchers concluded that executive-function weaknesses were“neither necessary nor sufficient to cause all cases of ADHD.”
In other words, executive-function difficulties appear to be an important part of ADHD, but they cannot explain everyone with the condition.
That matters.
ADHD isn't a single, identical experience shared by everybody who has the diagnosis. Two people can both have ADHD while experiencing quite different difficulties.
For me, this is also an important message for ADHD coaching.
Rather than starting with the assumption that somebody with ADHD must struggle with a predetermined list of executive functions, it makes more sense to start with the individual:
What is actually difficult for you?
Is it getting started? Remembering intentions? Planning? Staying focused? Managing competing priorities? Or something quite different?
Research like this reminds us to be careful about turning a useful explanation into an absolute one.
So, is ADHD an executive-function problem?
Executive-function difficulties are clearly an important part of the ADHD story. But they aren't the whole story.
And perhaps understanding that individual variation is just as important as understanding ADHD itself.
Research: Validity of the Executive Function Theory of Attention-Deficit/Hyperactivity Disorder: A Meta-Analytic Review, Willcutt et al. (2005), Biological Psychiatry.
Read the research summary [ohsu.elsev...erpure.com]