ADHD: What’s behind the recent explosion in diagnoses?
Discover New Scientist’s latest article on QbTest and how objective tests are helping improve standards for ADHD assessments.
Cases of attention deficit hyperactivity disorder are rocketing, but what’s the cause? Fortunately, we now have a better understanding of the condition – and how to identify those who have it.
I bet I can make you roll your eyes: I think I have ADHD. I imagine you are thinking: “Of course you have. How kooky. How creative. Now, go away and post about it on social media.” If so, I totally understand. Since I first saw a list of ADHD symptoms in the mid-2000s and had an “aha” moment, I have lost count of the number of times I have talked myself in and out of seeking a diagnosis.
At first, it was because the idea felt ridiculous. Back then, attention deficit hyperactivity disorder – to give it its full name – was for fidgety schoolboys. Fully grown women with a career and family need not apply.
Nearly 20 years later, I still feel ridiculous, but now it is because ADHD is so apparently fashionable. From celebrity interviews to conversations at the pub and between parents at the school gate, everyone is talking about it. These days, I am hesitating because I don’t want to jump on an increasingly crowded bandwagon.
Now, though, I have decided to finally find out what is going on – not only in my own brain, but in wider science and society. Is ADHD getting the recognition and understanding it deserves, or is the rise in interest a fad being pushed by drugs companies, online prescribers and attention-seeking influencers?
Getting answers matters. If ADHD is underdiagnosed we are letting huge numbers of people struggle. If the opposite, then we are pathologising, and drugging, normal human variation. And as new research questions the core nature of ADHD, we may even need to rethink this condition.
The first mention of a condition that seems similar to ADHD in medical texts was in 1798, when physician Alexander Crichton described the “incapacity of attending with a necessary degree of constancy to any one object”. According to Crichton, these people had their own name for what they experienced. “They say they have the fidgets,” he wrote.
Since then, the condition has been renamed many times. Between the 1930s and 1980s, it was known as hyperkinetic disorder. The modern name was coined by the American Psychiatric Association in the 1994 edition of the Diagnostic and Statistical Manual of Mental Disorders. Known as the DSM, this document provides official guidance on how to diagnose ADHD in the US. The World Health Organization’s International Classification of Diseases provides a similar list of diagnostic symptoms. In both systems, being a bit fidgety doesn’t cut it. To qualify for a diagnosis, you must have experienced problems with hyperactivity or inattention since childhood, and these symptoms must have a significant negative impact (see “Do you have ADHD?”).
There were certainly signs in my own childhood. According to my mum, I was “always on the go”, an exhausting chatterbox who followed her everywhere, singing, dancing and repeatedly falling down the stairs. As an adult, I am much the same, though you would have to live with me to notice. Aside from the fidgeting and fast-talking, these days it mostly manifests as messiness and domestic disorganisation. I don’t just forget appointments. I can forget them in the 10 minutes between the reminder pinging on my phone and the moment I should be leaving the house – more often than not, I get sidetracked on the way to the front door.
In my working life, some days I write at an alarming speed, knocking out thousands of words without blinking. On others, I spend hours staring into space, trying to concentrate and getting increasingly frustrated because it shouldn’t be this hard. There is little middle ground and nothing I do can turn a staring day into a writing day. It makes it impossible to plan my workload and incredibly stressful trying to juggle more than one deadline.
It isn’t all bad. Creativity and curiosity are two notable upsides, and if I believe my loved ones, they wouldn’t have me any other way. In some ways, my symptoms aren’t all that unusual; lots of people would describe themselves as disorganised. But when it affects everything you do, the lack of control over your own mind can be exhausting and cause more negative self-talk than is probably healthy.
How to get an ADHD diagnosis
Getting a diagnosis isn’t easy, at least in the UK, where waiting times range from six months to several years depending on where you live. I am currently three months into what I am told will be a six month wait on the National Health Service. But there are reasons to persevere. Research suggests that getting a diagnosis of ADHD in adulthood leads to not only better functioning in life and work, but improved quality of life and self-esteem. What’s more, when diagnosed, ADHD is highly treatable, including with drugs like methylphenidate or a mix of amphetamine and dextroamphetamine, better known as Ritalin and Adderall respectively (see “What is the best way to treat ADHD?”).
It is the use of these stimulant drugs that makes ADHD diagnosis more controversial than other common neurodevelopmental conditions, such as dyslexia or autism, which aren’t usually medicated. The use of stimulants, which can be addictive if misused, stirs in the perception that we, and our children, could be hijacked by the vested interests of big pharma, which profits from telling us there is something to fix.
This is a particular concern at the moment because many services have sprung up in the US offering speedy online diagnoses of ADHD and treatment plans. Because these services are for-profit, some worry that they may rush-through consultations and over-diagnose. Plus, ADHD is hugely popular on social media. On TikTok, posts labelled with the hashtag ADHD have 23 billion views.
Medical sociologist Peter Conrad at Brandeis University in Massachusetts has sounded warnings about this. In a 2014 paper, he and his colleague Meredith Bergey argued that the rise of ADHD has more to do with marketing than medical need. The expansion of criteria in successive versions of the DSM, particularly to include adults, they wrote, is a direct result of drug companies expanding into new, untapped markets.
What’s behind the rise in ADHD diagnoses?
It is also possible that diagnosis in children could be driven by parents’ desire to secure extra support for them. Getting a diagnosis of ADHD can unlock extra funds from local government that can be invaluable to children struggling at school. One 2018 study looked at children in the US and found that those living in states where these kinds of incentives exist were 15 per cent more likely to be diagnosed with ADHD and 22 per cent more likely to be medicated than those elsewhere.
Even with all this attention on ADHD, it isn’t easy to tell whether there is a rise in diagnoses, not least because authorities don’t tend to release figures on diagnoses per se. Instead, the best figures we have estimate rates of ADHD based on the number of people using stimulant drugs. These provide a good but not perfect picture because not everyone with ADHD uses stimulants and a small number use them to help with other conditions. Still, these estimates suggest that ADHD is indeed on the rise in Australia, England and the US, with the latter well ahead of the pack (see graph, below).
Prevalence of ADHD
Our best estimates suggest that ADHD diagnoses have been rising in England, Australia and the US. However, the proportion of people with a diagnosis is by far the highest in the US.
When you break down the data and look at individual age brackets it is clear that in the US, children make up the bulk of the cases. For example, one study that looked at parent-reported ADHD diagnosis and treatment estimated that 8.4 per cent of young people in the US aged between 2 and 17 had ADHD in 2016. The equivalent figures for the UK and Australia were below 2 per cent.
What kind of prevalence should we expect? We can get an idea from studies that look at randomly selected groups of people (rather than those that actively seek a diagnosis) and see how many exhibit symptoms of ADHD. A systematic review of such studies estimated the global prevalence of ADHD in children at 5.3 per cent. This suggests a nuanced picture. In the UK and Australia it seems that ADHD is being underdiagnosed while in the US we may be overdoing it.
When it comes to adults, studies of randomly selected people suggest the global prevalence of ADHD should be about 3 per cent, not dissimilar from that in children. In the US, the actual proportion of adults thought to have the condition (based on who takes stimulant medication) varies significantly depending on age group. Rates tend to be low in older people, but, for example, figures published by the US Centers for Disease Control show that 5 per cent of men aged 20 to 25 had ADHD in 2021. Rates of ADHD in adults are much lower in the UK and Australia. Last year, only 0.5 per cent of UK adults had a prescription for ADHD medication.
This means that, despite all the hype, in some age groups and in some places we are still underdiagnosing the condition in adults. “ADHD has been unrecognised and undiagnosed for many years, so we are starting from a very low point,” says Philip Asherson at King’s College London.
Another argument against ADHD being a fad, says Asherson, is that many of the people now seeking a diagnosis have previously sought help and been diagnosed with a different condition, such as anxiety or depression. We shouldn’t see the people now wondering if they have ADHD as having dreamed up the idea out of nowhere, says Asherson.
One way to tread the narrow path between overdiagnosis and leaving people struggling would be to have a quick, accurate way to sort people with a clinical condition from those who are in the typical range of human behaviour. So, the hunt is on for a tell-tale diagnostic marker that points directly to ADHD that rules out general distractibility once and for all.
How do we diagnose ADHD?
There are several candidates that could fit the bill. In children, electroencephalogram (EEG) studies, which monitor patterns in electrical activity across the brain, have suggested that ADHD may be associated with a higher ratio of theta brainwaves, linked with a “zoned-out” state, relative to more “on-task” beta brainwaves. In 2013, the US Food and Drug Administration (FDA) approved one commercial EEG device called NEBA as a diagnostic aid in children, which has started appearing in clinics across the US. Not everyone agrees that this application of EEG is ready for the clinic, though, and the evidence for using EEG as a biomarker in adults is unclear, says consultant psychiatrist Marios Adamou at the University of Huddersfield, UK.
Despite clear indications that ADHD runs in families, genetic analysis can’t tell us definitively who has it. A genome-wide study in 2018 analysed the DNA of more than 55,000 people, 20,000 of whom had ADHD. Twelve common gene variants increased the risk of a diagnosis, each adding a tiny amount of risk. As yet, though, there isn’t enough data to provide a threshold for diagnosis.
The most objective and user-friendly option available comes in the form of standardised cognitive tests. One variation, which is becoming widely used in the US and UK, is the so-called Qb (quantitative behavioural) test. This was adapted from psychological tests created in the 1950s to measure sustained attention. These alone couldn’t distinguish ADHD from other conditions that affect attention, so Swedish company QbTech added a motion-capture element to the test that records the movements of the head as a proxy for hyperactivity.
In late March, I visited the company’s London office to try the test myself. Charlotte Cooper, the firm’s clinical operations manager, took me into a featureless room and explained that the test is supposed to be boring. It involves watching a computer screen for 20 minutes while one of four simple shapes briefly appears on the screen. My task was to press the button if the symbol on the screen matched the one that came just 2 seconds before. It is simple enough, but the idea is that people with ADHD are more likely to zone out and then miss the short window to press the button when the symbols match – or impulsively press the button when they don’t.
Afterwards, Cooper ran me through my results. Surprisingly, to me at least, my fidgeting levels were in the normal range for my age and gender, as was my reaction time. My error rate, though, was significantly higher than controls: 93 per cent of people made fewer mistakes than me. Most of my errors involved hitting the button when I shouldn’t have. That sounds about right. Several times, I caught myself zoning out, snapped back and hit the button – as it turned out, in error. This might point to both inattention and impulsiveness, Cooper says. Indeed, the test showed that 97 per cent of people were less impulsive than me.
The test was approved to be used alongside standard medical interviews in the US by the FDA in 2016 and is currently being assessed by the equivalent body in the UK. In a recent randomised controlled trial, led by Chris Hollis at the University of Nottingham, UK, psychiatrists who used the QbTest alongside standard questionnaires and a consultation ruled people in and out of an ADHD diagnosis 15 per cent faster than those using questionnaires and interviews alone, and with no change in accuracy. With these kinds of objective tests, we are getting closer to making sure the right people get treatment.
Meanwhile, scientists are digging deeper into the core nature of the condition. In the past few years, several studies have begun exploring the links between ADHD and perception of time. Radek Ptacek at Charles University in the Czech Republic reviewed this work in 2019 and showed that people with ADHD have problems estimating how quickly time passes and this can be addressed with stimulant medication.
The underlying cause
He believes that a problem with the perception of time could be the true underlying cause of many ADHD symptoms. Restlessness may stem from a sense that time is dragging. An inability to keep track of time may cause problems with planning and memory. “People [with ADHD] talk about the sense that things are either now or not now, and they can’t make sense of what ‘not now’ is,” says Hollis. Poor time perception should be added to the next edition of the DSM as a core symptom, says Ptacek.
Other potential additions include problems with emotional control, which Asherson says “is now quite well established as a symptom that often accompanies ADHD”, and is often taken into account in diagnosis, even though it isn’t on the official list.
Then there are the little-known upsides: creativity, which seems to be above average in people with ADHD and may be a direct result of a brain that hops from subject to subject, making connections where others wouldn’t. There is also hyperfocus, the counterintuitive symptom that sees people with ADHD drawn deep into tasks that interest them for hours at a time – also known as the only reason I am ever able to finish an article.
In fact, some researchers argue that we need to rename the condition altogether, to reflect that there is no deficit of attention in ADHD, more a problem with the control over where it goes. My suggestion is attention regulation disorder, or ARD – which feels apt because, in my experience, it makes life way ARD-er than it needs to be.
At the time of writing, I am still waiting to reach the front of the queue for diagnosis. In the meantime, I can hang onto the knowing nods of Hollis and Asherson as I explained my struggles to them and the highly suggestive results of the QbTest. Interestingly, Asherson says that in his experience, people who self-diagnose based on what they have read about ADHD often turn out to be right. “So far, almost everyone who thinks they have it, does,” he says. I guess we will see.
Do you have ADHD?
ADHD is officially diagnosed following the guidance in the Diagnostic and Statistical Manual of Mental Disorders or the World Health Organization’s International Classification of Diseases. Both set out more or less the same criteria for diagnosis. There are symptoms of inattention, such as being easily distracted or making careless mistakes, and of hyperactivity, such as having trouble sitting still and interrupting people. Adults must have at least five of these symptoms (for children it is six) and these must have been around since before they were 12 years old. They must manifest in more than one setting, such as their work, home and social life. On top of that, all this must negatively affect their ability to function in those settings.
If you tick all those boxes then a doctor could diagnose you with ADHD. The diagnosis will come in one of three types. You could be predominantly inattentive, predominantly hyperactive or a “combined” type.
What is the best way to treat ADHD?
ADHD is considered highly treatable. For those who opt to try drugs, the first option is often a stimulant, such as methylphenidate (Ritalin), a mixture of amphetamine and dextroamphetamine (Adderall) or the lesser-known lisdexamfetamine (Vyvanse). According to a 2021 consensus statement from the World Federation of ADHD, methylphenidate has the best risk-benefit ratio for children and adolescents, while amphetamines work best for adults. Other drug-based options include non-stimulants such as atomoxetine, which boosts the neurotransmitter norepinephrine and therefore alertness. The blood pressure medications guanfacine and clonidine have also been found to reduce some symptoms and can be used with or instead of stimulants.
Alternatives include talking therapies such as cognitive behavioural therapy, which aims not to reduce symptoms, but to help people work around the challenges ADHD can bring in everyday life. There is some evidence in favour of brain training exercises, but large-scale trials have yet to be done and these methods are still considered experimental.
You should consult your doctor before starting medical treatment.