The global prevalence of childhood ADHD is estimated to be 5%, with significant variation between countries; US 8-10%, China~ 6%, Japan ~2.5%, UK ~5%, Europe ~4% and South Africa ~7.5%. Clinical referrals for suspected-ADHD are significantly increasing but ADHD remains under-recognised and under-diagnosed in many countries.

There are three subtypes of ADHD:

• Inattentive
• Hyperactive-impulsive
• Combined inattentive and hyperactive-impulsive

There is no evidence-based consensus on what the most common subtype is.

Childhood ADHD is most frequently diagnosed between the ages 4 and 7, around the time of transition to school attendance. It is diagnosed twice as commonly in boys. Boys may present with more overtly disruptive behaviour prompting earlier referral.

Girls predominantly have the inattentive subtype and less obvious symptoms, risking a delay of diagnosis into adolescence or adulthood.

 A significant reason for variable prevalence between countries is due to methods used in diagnosis. Higher incidence countries may rely more on parent or self-reporting of symptoms The DSM-5 and ICD-11 diagnostic criteria however have many overlapping similarities.

The DSM-5 criteria for ADHD diagnosis are

• the symptoms/behaviours have persisted for over 6 months, and
• are present in more than one setting (e.g. school and home), and that
• the symptoms interfere with functioning.

There are listed symptoms covering both inattentive type and hyperactive/impulsive behaviours. These symptoms must be "inappropriate for the developmental level", bearing in mind that there is a spectrum of developmental milestones for any child. Under the age of 17, six symptoms are necessary for diagnosis. Depending on the different categories the symptoms fall into for each patient, their ADHD subtype can be classified. There is also the qualifier that the symptoms need not to be better explained by another mental health disorder.

In 2013, DSM-5 changed the age, by which the symptoms needed to present, from 7 to 12. This extension in age threshold could partly account for an increase in childhood ADHD diagnoses.

ICD-11 differs slightly from DSM-5 with more symptoms listed for both inattention and hyperactive/impulsive symptoms. There isn't a specific number of symptoms that need to be exhibited to reach the cut off, which allows for flexibility in different cultural contexts e.g. where hyperactivity is less well tolerated.

ADHD is diagnosed behaviourally, without a laboratory test. Challenges to accurate diagnosis include the fact that inattention, impulsivity, and hyperactivity are normal childhood behaviours, and so evaluating what is "outside normal variation" (as is specified in ICD-11) requires sophisticated knowledge of child development. 

Assessment involves completion of questionnaires from both home and school environments, by parent/carers and teachers respectively, regarding which symptoms are displayed and their frequency. Other questionnaires help to rule out differential diagnoses such as autism or depression. Objective validated assessments such as the FDA and NICE approved QbTest_© can be undertaken, which monitors a child's ability to concentrate, their movements and tests impulsivity. NICE, in the UK, are evaluating a wider panel of providers, including EF Sim Test and Nesplora. The results are compared against age and gender norms. Following this an extended (usually 60-90 minute) assessment with a specialist would take place.

The potential causes of ADHD have been extensively studied, with many potential contributory risk factors identified. It is incompletely understood in terms of causation, and research continues apace to explore this further.

Discussions continue regarding whether ADHD is related to nature or nurture, i.e. whether it is driven by inheritance or environment, but studies have shown that both factors play an important role in the risk of developing ADHD.

Twin studies (which compare data from identical and fraternal twins to understand the contribution to risk by genetics and environment) have estimated the heritability of ADHD to be over 70% ¹ indicating a significant contribution from genetics.

Variants in certain gene loci have been identified as increasing ADHD risk ². This risk is polygenic (i.e. from multiple genes). Interestingly, many of these loci are in genes that are expressed in early brain development and include those previously identified as increasing risk for other psychiatric conditions, which may partly explain increased incidence of psychiatric comorbidities with ADHD.

 Studies looking at heritability of ADHD over time ³ have shown no significant changes in over three decades, suggesting that environmental changes have not contributed to the increasing prevalence of ADHD over recent times.

Environmental factors may contribute to genetic risk through epigenetic processes (altering gene expression without changing the underlying code). Multiple environmental factors have been shown to be associated with increased risk of developing ADHD, but direct causality has not been proven. Studies have found prenatal exposure to heavy metals, pesticides and even some simple medications like paracetamol, as well as maternal smoking and alcohol in pregnancy have shown an association with ADHD. Recent discussions around the use of paracetamol (acetaminophen) during pregnancy and its potential link to neurodevelopmental disorders such as autism and ADHD have reignited interest in the theory of in-utero exposure effects. A study by Hornig et al. (2017) reported a 40% increased risk of ADHD in children whose mothers experienced fever during the second trimester. The risk was notably higher — an adjusted odds ratio of 3.12 — when three or more fevers occurred after the 12th week of gestation.

More recently, Baker et al. (2025), reporting on the US CANDLE study in Nature Mental Health, found an association between prenatal paracetamol use and elevated rates of autism and ADHD. However, it is important to emphasise that association does not imply causation. The American College of Obstetricians and Gynaecologists (ACOG) continues to support the moderate use of paracetamol during pregnancy. They reference findings by Ahlqvist et al. in JAMA, which concluded that observed associations were likely due to familial confounding rather than a direct causal link.

Managing fever during pregnancy remains critical, as untreated fever can lead to serious perinatal complications including birth defects and preterm labour. Other factors such as maternal obesity, gestational diabetes, and low birth weight have also been associated with increased risk of neurodevelopmental disorders.

Children with ADHD are more likely to have a history exposure to Adverse Childhood Experiences (ACEs) compared to children without ADHD, with a higher ACE score correlating with more significant ADHD symptoms ⁴. Adverse childhood experiences might include physical, sexual or emotional abuse or neglect, parental separation and household substance abuse.

Different parenting styles have also been shown to affect ADHD symptoms- both positively and negatively. However, there is also the likelihood that the presence of ADHD symptoms affects the parenting style adopted as well ⁵.

Over the years there has been discussions about diet and ADHD risk, in particular the effects of food additives/colourings and refined sugar. There is some evidence that additives can exacerbate symptoms, but no evidence as a causative factor. In general, an unhealthy diet (high proportion of ultra-processed foods and refined sugar content) has been associated with an increased risk ⁶.

Studies looking at screen time in young (< age 3) children showed earlier age exposure and longer daily exposure to screens was associated with increased hyperactive behaviours ⁷. A study looking at screen time in adolescents ⁸ showed increased impulsivity with increased screen time, with social media use being more significant than television or video games. As the increase in screen time exposure has been a development in the last decade, it will be interesting to see how these trends are analysed in future studies.

Looking at these risk factors it is perhaps unsurprising that we see increased ADHD risk in lower socio-economic groups and with lower maternal education levels. It is also important to keep in mind that there may be alternative confounding explanations for the associations between environmental risk factors and ADHD.

Whereas adults with ADHD may be successfully managed with medication only, children more often need psychotherapy and occupational therapy in combination with stimulant medication.

 Psychotherapy in children has a different focus to that used in adults, with a focus on organisational skills rather than the adult focus on relationship or workplace challenges. It is also key to involve parents and school in therapy so that behavioural strategies and routine can be reinforced in all environments.

Medicating a child with ADHD comes with risks of side effects, however the improvement of symptoms with medication in ADHD can be significant. There are concerns that stimulant medication can reduce the height achieved by children (reducing final adult height by approximately 1 inch compared to estimated) however studies have shown that whilst growth might be stunted earlier in the treatment period, it does normalise later on. "Drug holidays" during summer breaks from school have been shown to counteract the effect on growth (but only if done more than once) and these strategies can be less popular with parents. ⁹

One theory for the effect on growth rate is the stimulants appetite suppression, leading to a reduction in calorie intake. Short acting medications can have less of an effect on appetite but overall adherence to treatment can be inferior to long-acting preparations.

Diet has been suggested to play a significant role in the development and severity of ADHD symptoms however generational diets are not taken into account in the studies e.g. mothers of children whose diets are healthier are more likely to have had a better diet during pregnancy. There have been suggestions that zinc, iron, magnesium and omega-3 fatty acid supplements can all improve ADHD symptoms ₆ (the latter has significant benefits for brain health in general) but there is currently insufficient evidence from well conducted studies to recommend them as part of management. Elimination diets can help identify "trigger" foods to avoid and can be tailored to an individual. A long-term significantly restricted "few-foods" diet is not recommended. In general, a balanced diet rich in whole foods and avoiding ultra-processed foods or sugar spikes is key in ADHD management.

Regular exercise helps improve focus and attention. A recent systematic review ¹⁰ found that memory and executive function improvements were higher in children with ADHD who performed either Exergames (video games with movement) or mind-body exercises such as Tai-Chi or Yoga.

Longitudinal studies have shown that up to 80% of children with ADHD will have symptoms that persist into adulthood. 15% will continue to experience symptoms enough to maintain a full ADHD diagnosis and approximately 65% will have a "partial remission" with the persistence of some symptoms only.

Inattentive symptoms are the most likely symptoms to persist.

Given the nature of symptoms, in the general population children with ADHD can have lower levels of educational attendance and achievement which may ultimately manifest in lower-ranking jobs. Whilst children with ADHD do have more challenges to overcome than their non-ADHD counterparts, the achievement of higher education goals is not precluded, and age-appropriate interventions and/or medication can support improved outcomes. Children with ADHD may be more prone to have low self-esteem and struggle socially ¹¹. In more severe cases and particularly during adolescence, there is increased risk of substance abuse and potential antisocial behaviours leading to criminal records. Prognosis will depend on the timeliness of diagnosis, any psychiatric co-morbidities and the effectiveness of instigated therapeutic interventions.

The impact in adulthood, including associations with physical conditions and employment considerations, is covered in Professor Hayes' article on adult ADHD.

A childhood diagnosis of ADHD could have implications for later insurability even if all symptoms do not persist into adulthood. Increased work absence risk exists with disability cover due to higher rates of burnout and comorbid mental health conditions, but there are also implications for life insurance and critical illness cover. Underwriting the applicant holistically, including co-existing psychiatric disorder, and the impact of therapeutics is key to a sensitive and evidence-based risk assessment.

On current application forms for adults there may be limited opportunities to declare an ADHD diagnosis. Whilst questions would pick up mental health conditions in recent years and would pick up if someone was currently medicated, specific application questions on neurodevelopmental disorder diagnoses are often not present.

When underwriting children with ADHD, particularly for Medical Expenses cover, it is important to consider current symptoms, whether they are awaiting assessment for a diagnosis, the presence of any comorbidities and the number of medications they are on.

From a claims point of view more generally, when an ADHD diagnosis is mentioned we need to consider whether this is self-reported or following a clinical diagnosis. There is also the consideration that, as a neurodevelopmental condition (which, by definition, would have been present all their life) it needs careful assessment and exclusion of potential non-disclosure of symptoms prior to the policy inception. This can be a difficult area to analyse when a claim is multifactorial and includes a retrospective diagnosis of ADHD in adulthood following a "burnout" episode in an employment setting. Non-disclosure is not a given, and expert review is recommended in order to provide an objective clinical scrutiny.

Insurers may see more declarations of ADHD diagnosis in coming years as awareness continues, stigmatisation reduces, and access (particularly to private assessment) increases. Studies ¹² suggest that although it may appear as if incidence is increasing that true prevalence hasn't increased over time, rather that more retrospective diagnoses are being made in adulthood. Like any underwriting process, the rules remain the same; ask reasonable questions, provide evidence-based assessments and communicate your rationale transparently. Our underwriting and claims teams, and medical officer community, are here to assist.