It’s the attention disorder affecting 2.5million Britons and a host of celebrities – but now experts warn ADHD’s restlessness, trouble concentrating and memory problems could all be symptoms of OTHER conditions… and they’re far easier to treat

Restlessness, trouble concentrating, impulsiveness and memory problems – all symptoms of attention deficit hyperactivity disorder (ADHD).

But as diagnoses of the condition continue to rise – in England alone an estimated 2.5million people have ADHD, including celebrities like Lily Allen, Robbie Williams and Olivia Attwood – an intriguing question is emerging. Could some people with these common symptoms not have ADHD at all, but another medical condition – one that may be far easier to treat?

The thinking has long been that the brains of people with ADHD are wired differently and that, for those worst affected, powerful stimulant medications can help them focus.

But the truth is some symptoms associated with ADHD can have other causes. And there’s concern these may not always be adequately ruled out before a diagnosis is made – particularly as NHS waiting lists for an ADHD assessment stretch to seven years in some areas, prompting many to turn to private clinics where assessments may take place online.

Professor Dinesh Bhugra, former president of the Royal College of Psychiatrists, said: ‘No one is saying that people with genuinely disabling symptoms from ADHD should be denied the help they need to function.

‘But there is a question, in some cases, over whether it is actually ADHD, or whether it could be something else – and I don’t know whether those additional checks to rule out other conditions are always being made.

‘It’s vitally important that people get the right diagnosis. Giving them stimulants when they don’t need them is not going to help, and we don’t yet know the long-term consequences of being on these drugs.

‘Professionals making ADHD assessments need to look at multiple facets rather than just running through a symptom checklist.’

Indeed, a major review of the evidence in 2023 by Canadian psychiatrist Joseph Sadek identified several conditions which may be ‘misdiagnosed as ADHD’, ranging from thyroid problems to iron deficiency. It concluded that everyone being assessed for ADHD should undergo a ‘thorough medical evaluation’ to check for conditions that may mimic it before a diagnosis is made.

An important clue is when the symptoms first appeared. As Dr Dan Baumgardt, a GP and senior lecturer at the University of Bristol, points out: ‘Symptoms of ADHD don’t generally appear in adulthood – there’s usually a trail that leads back to childhood as it’s a lifelong condition. If symptoms suddenly appear, it becomes more likely there’s another cause which should be investigated.’

This is significant because adult ADHD diagnoses have doubled over the past two decades.

So what else could be causing ADHD-like symptoms?

Problems with high blood sugar

Diabetes, a chronic condition that causes blood sugar levels to become too high, can also trigger symptoms that resemble ADHD.

The 2023 Canadian review found that people with type 1 diabetes – an autoimmune condition in which the pancreas produces little or no insulin, the hormone that helps control blood sugar – can have poorer memory and academic performance in childhood, as well as problems with attention in adulthood. Type 2 diabetes, which is strongly linked to excess weight, has also been associated with problems with memory and attention, the review found.

Dr Baumgardt says: ‘Diabetes is known to cause fatigue and cognitive issues, and that might look a bit like ADHD in some cases. But it’s treatable – in type 1, patients will need to take insulin, and, in type 2, diet and lifestyle can help, as can tablets such as metformin.’

Both types can be picked up with a simple blood test ordered by a GP.

The signs that it could be a hormonal issue

Thyroid problems are common and can go undiagnosed, yet both an underactive or overactive thyroid can cause symptoms that resemble ADHD.

The thyroid is a butterfly-shaped gland in the neck which produces hormones that help control how the body uses energy. An underactive thyroid – known as hypothyroidism – means the body does not produce enough thyroid hormone, which can cause fatigue, brain fog, difficulty concentrating and memory problems.

An overactive thyroid, known as hyperthyroidism, produces too much, and causes restlessness, irritability and trouble concentrating. Dr Baumgardt adds: ‘They can be underdiagnosed, and we need to look at whether people are slipping through the net.’

About 2 per cent of the population have 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 medicines that reduce the amount of thyroid hormone produced.

Hormonal changes during perimenopause can also produce symptoms that resemble ADHD, including brain fog, forgetfulness and difficulty concentrating.

There is an important distinction, however. Dr Baumgardt says some women may have had ADHD since childhood but successfully coped with the symptoms until hormonal changes around perimenopause made them more difficult to manage – eventually leading to a diagnosis.

But if problems with attention and memory have appeared for the first time in midlife, there may be another explanation.

‘If they’re new symptoms, and you’re also noticing things like hot flushes, night sweats and insomnia, then the menopause is the most convincing explanation and HRT may help,’ he says.

Is it other mental health struggles?

The lines between ADHD and other mental health conditions, particularly depression and anxiety, can ‘blur quite a bit’, says Dr Baumgardt.

Depression can cause poor concentration, forgetfulness and a lack of motivation, while anxiety can lead to restlessness, difficulty focusing and racing thoughts – all of which are also associated with ADHD.

The overlap may be especially important in children, among whom mental health problems have risen 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 attending A&E in a mental health crisis between 2019 and 2025. The steepest increase was among those aged six to nine – around the age that concerns about ADHD commonly emerge. Dr Iona Heath, former president of the Royal College of GPs, says: ‘Have you ever tried to sit still when angry, frightened or intensely worried? For far too many people – including children – these are near-continuous states.’

But complicating matters further, depression, anxiety and ADHD can also exist alongside one another. Dr Baumgardt says it takes professional expertise to tease apart the symptoms and establish what is being caused by ADHD and what might have another explanation.

‘The treatments are different – not just in terms of drugs but talking therapies, too,’ he says. ‘For some people, antidepressants could be transformative. Getting the right diagnosis can really help guide treatment.’

A comprehensive ADHD assessment should therefore look beyond a checklist of symptoms, considering when they began, how they affect different areas of a person’s life and whether another mental health condition could better explain them.

Why low iron levels have to be ruled out

Low iron is remarkably common – particularly among women – and it 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 impair the absorption of iron, or simply not getting enough from food, with those following plant-based diets potentially at greater risk.

Haematologist Dr Sue Pavord, of the University of Oxford, says iron levels should be checked in anyone being assessed for ADHD.

‘Before anyone is labelled they need to have treatable causes ruled out, and things like iron deficiency are just so incredibly common in children and young adults,’ Dr Pavord says. ‘You see all sorts of similarities in symptoms to ADHD and, even if it is ADHD, it might contribute to the severity of symptoms.

‘It’s easily treated with tablets or an iron infusion. All teenagers should be screened for low iron, perhaps at the same time as they get the HPV vaccine.’

Vitamin B12 deficiency can also cause neurological problems, including brain fog, difficulty concentrating and memory problems.

Link with snoring and sleep disorders

‘Children who have insomnia, or don’t get enough sleep, can find their attention is affected the following day,’ says Dr Baumgardt. ‘It can also make them hyperactive, rather than tired, which could be mistaken for ADHD.’

Indeed, the American Academy of Pediatrics recommends screening those seeking an ADHD assessment for sleep problems.

Obstructive sleep apnoea – a sleep disorder which causes breathing to stop and start and is thought to affect about eight million people in the UK – can also affect concentration and attentiveness as it disrupts normal sleep. GPs can refer to NHS sleep clinics for an assessment. Treatment might involve losing weight, stopping smoking and reducing alcohol intake, while others may need to wear a continuous positive airway pressure (CPAP) mask at night which delivers a flow of air to keep airways open.

Dr Baumgardt says: ‘It would be interesting to see what capacity private clinics have to consider other things, and whether they’re trained to order other tests and investigations to rule out other conditions.’