Restlessness, concentration problems, impulsiveness and memory problems – all symptoms of attention deficit hyperactivity disorder (ADHD).
But as diagnoses of the condition continue to rise – an estimated 2.5 million people in England alone have ADHD, including celebrities such as Lily Allen, Robbie Williams And Olivia Attwood – an intriguing question arises. Could some people with these common symptoms not have ADHD at all, but another medical condition – one that may be much easier to treat?
It has long been thought that the brains of people with ADHD are wired differently and that powerful stimulant medications can help them concentrate.
But the truth is that some symptoms associated with ADHD may have other causes. And there are concerns that these cannot always be sufficiently ruled out before a diagnosis is made, especially if NHS Waiting lists for an ADHD test can be as long as seven years in some areas, prompting many to turn to private clinics where tests can take place online.
Professor Dinesh Bhugra, former president of the Royal College of Psychiatrists, said: ‘No one is saying that people with truly disabling symptoms of ADHD should be denied the help they need to function.
‘But in some cases the question is whether it is actually ADHD, or whether it could be something else – and I don’t know whether those extra checks to rule out other conditions are always done.
‘It is crucial that people get the correct diagnosis. Giving them stimulants when they don’t need them won’t help, and we don’t yet know the long-term consequences of taking these drugs.
“Professionals making ADHD assessments need to look at multiple facets rather than just reviewing a symptom checklist.”
Lily Allen revealed her ADHD diagnosis three years ago, saying the condition ‘runs in my family’
Former Take That singer Robbie Williams was diagnosed with ADHD twenty years ago
TV presenter Olivia Attwood, who appeared in the third series of Love Island, also has ADHD
A major 2023 review of the evidence by Canadian psychiatrist Joseph Sadek identified several conditions that could be “misdiagnosed as ADHD,” ranging from thyroid problems to iron deficiency. It concluded that anyone assessed for ADHD should undergo a ‘thorough medical evaluation’ to check for conditions that could mimic it before a diagnosis is made.
An important clue is when the symptoms first appeared. As Dr Dan Baumgardt, GP and Associate Professor at the University of Bristol, notes: ‘Symptoms of ADHD do not generally appear in adulthood – there is usually a trace back to childhood because it is a lifelong condition. If symptoms suddenly appear, it increases the likelihood that there is another cause that needs to be investigated.”
This is important because the number of ADHD diagnoses in adults has doubled over the past twenty years.
So what else can cause ADHD-like symptoms?
Problems with high blood sugar levels
Diabetes, a chronic condition that causes blood sugar levels to rise too high, can also cause symptoms similar to ADHD.
The 2023 Canadian study found that people with type 1 diabetes — an autoimmune disease in which the pancreas produces little or no insulin, the hormone that helps control blood sugar levels — may have poorer memory and academic performance in childhood, as well as problems with attention in adulthood. Type 2 diabetes, which is strongly linked to being overweight, is also linked to problems with memory and attention, the review found.
Dr. Baumgardt says: ‘Diabetes is known to cause fatigue and cognitive problems, which can be a bit like ADHD in some cases. But it is treatable: with type 1, patients must take insulin, and with type 2, diet and lifestyle can help, as can tablets such as metformin.’
Both types can be detected with a simple blood test ordered by a GP.
The signs that it could be a hormonal problem
Thyroid problems are common and often go undiagnosed, but both an underactive and overactive thyroid can cause symptoms similar to ADHD.
The thyroid is a butterfly-shaped gland in the neck that produces hormones that help control how the body uses energy. An underactive thyroid gland – known as hypothyroidism – means the body does not produce enough thyroid hormone, which can cause fatigue, brain fog, concentration problems and memory problems.
An overactive thyroid gland, known as hyperthyroidism, produces too much and causes restlessness, irritability and difficulty concentrating. Dr. Baumgardt adds, “They may be underdiagnosed, and we need to see if people are slipping through the net.”
About 2 percent of the population has an underactive thyroid, with more women affected, while an overactive thyroid is less common. Both can be detected with a blood test.
An underactive thyroid is usually treated with daily levothyroxine tablets to replace the missing hormone, while an overactive thyroid can be treated with drugs that reduce the amount of thyroid hormone produced.
Hormonal changes during perimenopause can also cause symptoms similar to ADHD, including brain fog, forgetfulness, and difficulty concentrating.
However, there is an important distinction. Dr. Baumgardt says some women have had ADHD since childhood but were successfully managing the symptoms until hormonal changes around perimenopause made it more difficult to manage, eventually leading to a diagnosis.
But if problems with attention and memory first appeared in middle age, there may be another explanation.
‘If these are new symptoms, and you also notice things like hot flashes, night sweats and insomnia, then menopause is the most convincing explanation and HRT can help,’ he says.
Are they other mental health issues?
The lines between ADHD and other mental health conditions, especially depression and anxiety, can be “quite blurred,” says Dr. Baumgardt.
Depression can cause poor concentration, forgetfulness and a lack of motivation, while anxiety can lead to restlessness, difficulty concentrating and racing thoughts – all of which are also linked to ADHD.
The overlap may be especially important in children, among whom mental health problems have increased sharply.
The Royal College of Paediatrics and Child Health has reported a 36 per cent increase in the number of children aged six to 17 going to A&E during a mental health crisis between 2019 and 2025. The strongest increase occurred among children between the ages of six and nine – around the age when concerns about ADHD often arise. Dr. Iona Heath, former president of the Royal College of GPs, says: ‘Have you ever tried to sit still when you were angry, scared or intensely worried? For far too many people – including children – these are almost continuous conditions.’
But what complicates matters further is that depression, anxiety, and ADHD can also coexist. Dr. Baumgardt says it takes professional expertise to tease apart the symptoms and determine what is caused by ADHD and what might have another explanation.
“The treatments are different – not just in terms of medications, but also in terms of talking therapies,” he says. ‘For some people, antidepressants can be transformative. Making the correct diagnosis can really help guide treatment.’
A comprehensive ADHD assessment must therefore look beyond a checklist of symptoms, taking into account when they started, how they affect different areas of a person’s life, and whether another mental health condition could better explain them.
Why low iron levels should be ruled out
Low iron levels are remarkably common – especially among women – and can cause poor concentration, restlessness, inattention and memory problems.
It can also be caused by heavy menstrual bleeding, digestive disorders such as Crohn’s disease, which hinder iron absorption, or simply not getting enough from food, with those following a plant-based diet potentially at greater risk.
Of the 2.5 million diagnosed ADHD patients in Britain, 741,000 are children and young adults.
ADHD is listed as the main condition for more than 100,000 disability benefit claimants each year.
Hematologist Dr Sue Pavord from the University of Oxford says iron levels should be checked in anyone being assessed for ADHD.
“Before someone is labeled, treatable causes must be ruled out, and things like iron deficiency are so incredibly common in children and young adults,” says Dr. Pavord. ‘You see all kinds of similarities in symptoms with ADHD and even though it is ADHD, it can contribute to the severity of the symptoms.
‘It is easy to treat with tablets or an iron infusion. All teens should be screened for low iron, perhaps at the same time as the HPV vaccine.”
Vitamin B12 deficiency can also cause neurological problems, including brain fog, concentration problems and memory problems.
Link with snoring and sleep disorders
“Children who have insomnia or don’t get enough sleep may find that their attention is affected the next day,” says Dr. Baumgardt. “It can also make them hyperactive instead of tired, which can be mistaken for ADHD.”
Indeed, the American Academy of Pediatrics recommends that people seeking an ADHD assessment be screened for sleep problems.
Obstructive sleep apnea – a sleep disorder that causes breathing to stop and start and is thought to affect around eight million people in Britain – can also affect concentration and attention by disrupting normal sleep. GPs can refer to NHS sleep clinics for an assessment. Treatment may include losing weight, quitting smoking, and reducing alcohol intake, while others may need to wear a CPAP (Continuous Positive Airway Pressure) mask at night that provides airflow to keep the airways open.
Dr. Baumgardt says, “It would be interesting to see what capacity private clinics have to consider other things, and whether they are trained to order other tests and investigations to rule out other conditions.”
