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Adult ADHD: Causes and symptoms

Mental Health Pregnancy

Attention deficit hyperactivity disorder – ADHD for short – is a condition that’s often thought of as a childhood behavioural problem. But adults can be affected by ADHD too.
Perhaps the reason it’s largely seen as a children’s issue is that the symptoms of ADHD typically first appear in children aged between three and seven years old (i). But sometimes the symptoms aren’t recognised until a child is older, or even until they’re an adult (ii).

Can you develop ADHD later in life?

If you have adult ADHD, it doesn’t mean that you develop the disorder as an adult. Despite the fact it’s called adult ADHD the symptoms are believed to always start in childhood – even if they aren’t recognised until much later. Indeed ADHD is no longer classed as a childhood disorder but rather as a chronic lifelong disorder – though the symptoms can often become milder as you get older (iii).
Like childhood ADHD, adult ADHD is a mental health disorder that causes problems such as having difficulties paying attention, hyperactivity and impulsive behaviour. The Mental Health Foundation says studies suggest it affects certain areas of the brain that help you solve problems, plan ahead, understand other people’s actions and control your impulses (iv).
According to the Royal College of Psychiatrists, as you get older the hyperactivity aspect of ADHD tends to improve, but other symptoms such as impulsiveness, poor concentration and risk taking can become worse (v). These can all affect many aspects of your life, making it hard for you to work and deal with other people. This may explain why those with adult ADHD have a higher-than-average risk of experiencing mental health issues such as depression, anxiety and low self-esteem (v).

How common is it?

Childhood ADHD is more common than adult ADHD. Royal College of Psychiatrists experts claim up to six in every 100 school-aged UK children affected, with one in seven children with ADHD continuing to experience symptoms as adults (v). Studies suggest that, globally, five per cent of all children and adolescents and 2.5 per cent of all adults have ADHD, with the prevalence in Europe estimated at between one and eight per cent (iii).
According to the UK mental health service provider Clinical Partners, 33 per cent of adults with ADHD have problems with attention – such as staying focused and doing ordinary daily tasks – with seven per cent having more significant problems with hyperactivity and impulsivity. About sixty per cent of adults with ADHD have a combination of both inattention and hyperactivity/impulsivity (vi).
Yet while boys are three times more likely to be diagnosed with ADHD than girls, experts suggest the fastest group of people currently being diagnosed with adult ADHD is women – and in particular, mothers (vii). Indeed, up to 75 per cent of women with ADHD aren’t being diagnosed with the disorder, they add. This may be because the symptoms can be less obvious in women than in men, or that normal female hormone fluctuations may be masking them.
Indeed, adult ADHD may be under diagnosed in general, says a report by the educational charity, Demos, which suggests many adults are not being diagnosed with or treated/supported for the disorder (viii). The report adds adults with ADHD are less likely to be in full-time, paid work than those without the condition, and that their work productivity may also be reduced – and too many, it argues, go through life without the support they need. 

What triggers ADHD in adults?

We don’t really know what causes ADHD. But it’s unlikely to be caused by any single factor, rather a combination of two or more, including:
Family history   According to the NHS ADHD tends to run in families, which suggests genetics plays a part (ix). For instance, parents, brothers and sisters of children with ADHD are more likely than others to have the disorder too (according to the Royal College of Psychiatrists, a third of those with ADHD have at least one parent with similar symptoms (iv)). In fact, in most cases, your genes are seen as a significant factor in developing ADHD. It’s not, however, thought to be related to a single gene – experts believe it’s more complicated than that.
Brain differences   There may be several differences in the make-up and function of the brains of people with ADHD compared with those of the rest of the population – though nobody’s really sure how significant this may be in terms of the disorder’s development (ix). For instance, if you have ADHD some areas of your brain may be smaller or larger than other people’s brains. You may also have a different balance of brain chemicals (neurotransmitters) compared to someone without ADHD, or some of those chemicals may not work in the same way.
Environmental exposures   There’s also an increasing amount of evidence to suggest being exposed to environmental factors at an early age or even in the womb may increase a child’s risk of developing ADHD (iv). For instance, environmental toxins, such as lead – which is often found in paint and pipes in older buildings – may increase a child’s risk of developing the disorder. One study also found that exposure to chemicals used to make plastic products – namely phthalates and bisphenol A – may be another possible factor in the disorder’s development, as well as exposure to nicotine, alcohol and other drugs (x).
Social factors   Some experts believe there are many indicators to suggest ADHD isn’t just a biological phenomenon, but that things such as social deprivation and early life stress may be involved too (x). Poverty and lack of access to resources may also  play a part. Meanwhile some of the other things that are thought to increase the risk of developing ADHD include:

  • Being born prematurely (before week 37 of pregnancy) or being born with a low birth weight

  • Epilepsy

  • Brain damage (including that caused by damage in the womb or having a severe head injury)

  • Other mental health disorders such as anxiety, depression and other mood disorders, autism, learning difficulties and conduct disorder.


What are the signs and symptoms of ADHD in adults?

Childhood ADHD symptoms have been well defined and you probably already know about some of them, such as having a short attention span, being easily distracted, constantly fidgeting or being unable to sit still or concentrate.
In adults, however, ADHD symptoms tend to be more subtle and difficult to define. This may well be because it hasn’t been as well studied as childhood ADHD. But what we do know is that, by the age of 25, around 15 per cent of adults diagnosed with ADHD during childhood still have all their symptoms, with 65 per cent having some symptoms (xi).
The NHS offers the following as a list of symptoms associated with adult ADHD (xi):

  • Carelessness and lack of attention to detail

  • Constantly starting new tasks before finishing old ones

  • Poor organisational skills

  • Inability to focus or prioritise

  • Constantly losing or misplacing things

  • Forgetfulness

  • Restlessness and feeling on edge

  • Difficulty keeping quiet, and speaking out of turn

  • Blurting out responses and often interrupting others

  • Mood swings, irritability and a quick temper

  • Inability to deal with stress 

  • Extreme impatience 

  • Taking risks in activities, often with little or no regard for personal safety or the safety of others (driving dangerously, for example)

Some of the other things that have been linked with adult ADHD include fatigue (caused by hyperactivity, for instance), misuse of alcohol and other drugs, hyperfocus (the opposite of lack of focus, where you’re so focused on something you lose track of everything and everyone around you), lack of motivation, irritability and having low self-esteem.

Conditions related to adult ADHD

If you’re an adult with ADHD you also have a risk of having other problems or conditions at the same time. According to the NHS, the most common of these related conditions is depression (xi). Others include:

  • Generalised anxiety disorder 

  • Personality disorders (borderline personality disorder or antisocial personality disorder,  for instance – these cause difficulties in how you relate to yourself and others, as well as problems coping with daily life)

  • Social phobias

  • Bipolar disorder (this causes moods that swing from one extreme to the other)

  • Obsessive compulsive disorder (also called OCD this is when you have obsessive thoughts and compulsive behaviours)

  • Sleep problems (difficulty getting to sleep or waking during the night, for instance)

  • Obesity (one study suggests obesity is linked with ADHD both in childhood and adulthood, with males more affected than females – it also claims food addiction is often associated with the disorder (x))

  • Dependency on digital and social media (an increasing amount of evidence suggests many adults with ADHD are affected by problematic internet use, including compulsive internet use, social media addiction and video game addiction (x)).


How is adult ADHD treated?

The signs and symptoms of adult ADHD can be hard to spot and therefore difficult to diagnose. This is partly because some other conditions can cause similar symptoms – some of which can also coexist with ADHD (see above) – including:

  • Thyroid conditions

  • Anxiety and depression

  • Bipolar disorder

  • Autism

  • Personality disorders

  • Substance use disorders

  • Brain injuries

  • Low blood sugar (hypoglycemia)

Meanwhile certain drugs and medications can mimic ADHD symptoms, including alcohol, caffeine, nicotine, steroids, antihistamines, anticonvulsants and beta-agonists (medicines used to treat asthma or COPD).
However if you think you may have one or more of the symptoms of adult ADHD, it’s a good idea to have a chat with your GP. They may refer you to a specialist for an assessment if you’ve had symptoms since you were a child – but weren’t diagnosed with ADHD then – or if the symptoms can’t be explained by any other mental health condition. If you were diagnosed with ADHD as a child or teenager, and your symptoms are making it difficult for you to function, you may also need to see a specialist.
Diagnosing the disorder in adults is, however, more difficult than in children. Plus according to the NHS, current diagnostic guidelines state you can’t be diagnosed as having adult ADHD unless you also had symptoms as a child – which may not be an easy thing for some people to remember (xiii).
Also, to be diagnosed with adult ADHD your symptoms should be having at least a moderate effect on your day-to-day life – such as finding it difficult to keep up at work or having relationship problems because of your symptoms.
If you are diagnosed by a specialist, your treatment options include medicines and therapies:
ADHD medicines   There are currently several types of medicines licensed to treat ADHD in children and adults, including stimulant medicines that act on certain parts of the brain to improve things like attention, concentration and behaviour. There’s also a non-stimulant medicine for ADHD that works by increasing the level of a chemical called noradrenaline in the brain to boost concentration and help control impulsive behaviour.
All of these medicines, however, come with potential side effects, which your GP or specialist will discuss with you.
Therapy   There are also a few different types of therapies that are useful in treating adult ADHD. These may also help treat some of the disorders that can exist alongside ADHD, such as anxiety. One of these therapies is cognitive behavioural therapy (CBT), which aims to help you cope with your problems by changing the way you think and behave around them.
Besides the treatments you may be offered by a specialist you can get support, advice and information from the following self-help groups for adults with ADHD that operate in the UK:
UK Adult ADHD Network

Living with adult ADHD

If you have adult ADHD, making sure your lifestyle is as healthy as possible could help you manage your symptoms. Some of the things you may want to consider include the following:

Eat well

Adults and children with ADHD may have an increased risk of becoming obese, so it’s important to eat a healthy, balanced diet with limited amounts of fatty, sugary foods. Eating well, says the Mental Health Foundation, can also improve your sense of wellbeing and your mood (xiv). In fact it’s widely thought that what you eat is associated with how you feel. For instance, researchers have found eating a Mediterranean-style diet supplemented with fish oils may help reduce the symptoms of depression (xiv).
Try eating plenty of fruit and vegetables – at least five portions every day – as well as whole grains, some lean protein and some healthy fats. Meanwhile it may be worth avoiding or at least limiting foods that can have a negative effect on your mood, including stimulants like alcohol, caffeine and chocolate.
You may also find that certain foods tend to make your symptoms worse – foods with additives, for instance (though there’s no real evidence to back this up). Keeping a record of everything you eat as well as your symptoms can help you to pinpoint any potentially aggravating foods, which you may then want to avoid (asking a nutritionist for advice about eliminating any foods from your diet can be helpful as it can help prevent nutritional deficiencies).

Keep active

Exercising releases chemicals in your brain that can improve your mood and generally make you feel better (plus it can help you keep your weight in check).
Aim for at least 150 minutes of moderate activity every week – you can break those minutes up any way you like, such as a 30-minute session five times a week. Moderate activity should leave you feeling warm and your heart pumping, but you shouldn’t be completely out of breath.
If you can exercise outdoors, that’s even better. According to the Mental Health Foundation, research suggests being in nature can make you feel happier as well as reduce the symptoms of depression and anxiety (xv). Try taking a walk in your nearest park, join a rambling group or just get out into your garden (digging, weeding and mowing are ideal ways to keep fit). When you can’t get outside, choose an indoor activity you enjoy doing that will help keep you more active, such as swimming, dancing or following an online exercise class.

Get plenty of sleep

People with adult ADHD can often find it difficult to sleep well – they may, for instance, struggle to get to sleep or wake up frequently throughout the night. But not getting enough sleep could make your symptoms worse.
If you’re taking medication for ADHD, tell your GP about any sleep problems you’re having, as you may need to switch to another medicine. In the meantime there are lots of tips on getting a good night’s sleep in our guide to sleep and insomnia.

Take charge of stress

Adult ADHD can affect all areas of your life, so it’s not surprising that it can stress you out – which can play havoc with your symptoms. If you’re finding it hard to cope with stress, try learning ways of managing it more effectively. Finding ways of relaxing can be a big help, so consider making time for things that could help make you feel more calm, such as meditation, mindfulness and deep breathing (read more about breathing exercises for stress at 
There are lots more tips on coping with stress in our guide to stress symptoms and signs.

Get organised

Many adults with ADHD find it difficult to stay organised. If this happens to you, try keeping a diary and writing down the things you need to do, make lists or write reminders on Post-It notes and put them in places you’re bound to see them regularly (you could try using different coloured notes for different types of tasks, or use coloured marker pens to highlight different tasks on your lists or in your diary).
If you find yourself feeling overwhelmed because you have too much to do, try to be more realistic and only take on as much as you can manage at home, at work and socially. Breaking down big tasks into smaller, more manageable steps can also be helpful.

Limit digital time

Having adult ADHD can make you spend a lot of time on the internet, including on social media and playing video games. This can mean you don’t spend enough time on the other things you should be doing, which can cause problems both at home and at work.
Try putting a time limit when you use digital devices – use a timer if that helps. Also switch off your devices when you’re trying to focus on something, and particularly about an hour or so before you go to bed, as it may help you get a better night’s sleep. If you feel you can’t live without social media, read our guide to how it affects mental health, which includes advice on how to cut down.

ADHD support for adults

Living with adult ADHD can be a real challenge. But there are lots of ways to help yourself.

Does nutrition help with ADHD?

In addition to making your lifestyle as healthy as possible, you may also want to consider taking a nutritional supplement to help improve your quality of life. Always check with your GP before taking any nutritional supplements if you’re also taking ADHD medication, as some nutrients can interfere with their absorption.
High-strength fish oils   The omega 3 fatty acids found in oily fish such as salmon, sardines and mackerel are needed for proper brain function and development, and studies involving children with ADHD suggest omega 3 supplements could also have beneficial effects on their symptoms – though some researchers claim they may be more effective on those who have mild ADHD (xvi).
If you’re a vegetarian or vegan you can still benefit from an omega-3 supplement, thanks to the availability of products that contain the natural triglyceride (TG) form of omega-3 (this is sourced from marine algae rather than from fish).
Zinc   This is also an important nutrient for brain health, found in foods such as dairy products, meat, poultry, beans, whole grains and fortified cereals. One review of studies into childhood ADHD suggests zinc supplements may help reduce ADHD symptoms in those who are deficient or have a high risk of deficiency (xvii).
Iron   The same review found iron supplements may be beneficial too if you have ADHD and you’re deficient in iron or at high risk of deficiency (xvii). Meanwhile, an earlier study suggests iron deficiency may increase the risk of mental health problems in both children and young adults (xviii).
Iron is found in a range of foods including liver, red meat, nuts, dried fruit, beans and fortified foods. However some people may be more at risk of being deficient in iron than others, including women who have heavy periods. If you think you’re not getting enough iron in your diet, consider trying a gentle form of iron that won’t upset your stomach, such as iron citrate or iron bisglycinate – or speak to your GP.
Magnesium   There aren’t currently many studies that investigate whether or not magnesium supplements might help with the management of ADHD symptoms – though one report suggests many children with ADHD may have a magnesium deficiency, and that taking magnesium supplements could improve some of their cognitive functions (xix).  We also know magnesium is an important mineral for brain health, plus it can help with sleep and relaxation, which can be very helpful if you have adult ADHD.
Vitamin C   It may also be a good idea to make sure you’re getting plenty of vitamin C, as there is some evidence to suggest vitamin C supplements may improve ADHD symptoms (particularly hyperactivity) in children – though the study also used flaxseed oil, which contains omega 3 fatty acids (xx). Another reason to take vitamin C is that it helps with iron absorption.
Again, vitamin C is found in many foods including a wide range of fruits and vegetables such as oranges, blackcurrants, strawberries, peppers, broccoli and potatoes. But if you’re not eating that healthily for any reason you may not be getting enough.
Vitamin D   Also important for a healthy brain, vitamin D has been linked with disorders such as ADHD, with one study suggesting many children with ADHD may have lower levels of vitamin D in their blood and could be more likely to be deficient (xxi). The researchers also found the children in the study who were given vitamin D supplements showed improvements in brain functions including hyperactivity, impulsivity and inattention. Another study has found taking vitamin D supplements alongside an ADHD medicine may help reduce ADHD symptoms in children (xxii).
If you’re considering taking a vitamin D supplement the recommended form is vitamin D3 (cholecalciferol), as this is the natural form of vitamin D our bodies make when we’re exposed to sunlight. You can get these in tablet form as well as in veggie-friendly drops. Most vitamin D3 supplements aren’t suitable for vegans, however, since they’re made from the fat of lamb’s wool. But the good news is you can get vegan vitamin D3 supplements available these days that are sourced from lichen.
For more advice on a range of wellbeing issues, visit our pharmacy health library  to see what you can find out.


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Disclaimer: The information presented by Nature's Best is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications.

Our Author - Christine Morgan


Christine Morgan has been a freelance health and wellbeing journalist for almost 20 years, having written for numerous publications including the Daily Mirror, S Magazine, Top Sante, Healthy, Woman & Home, Zest, Allergy, Healthy Times and Pregnancy & Birth; she has also edited several titles such as Women’ Health, Shine’s Real Health & Beauty and All About Health.

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