The diagnosis and treatment of adult ADHD

Over 20 per cent of adults attending adult community mental health services in Ireland screen positive for ADHD symptoms

Unlike almost all of psychiatry and psychology, attention deficit hyperactivity disorder (ADHD) has inspired very few films or novels. But there is one prominent exception. In Rick Riordan’s Percy Jackson series of children’s books, the protagonist is a modern-day demigod loosely based on the ancient Greek hero Perseus. Both are sons of gods (Zeus and Poseidon), and both encounter the Gorgon Medusa during the course of their adventures. It seems unlikely Perseus was neurodivergent, but Percy Jackson is certainly described as so. “That’s all cool with me,” he narrates, “I mean, I’m ADHD and dyslexic, like most half-bloods, so I’d never done that great in regular schools even before they kicked me out.”¹

ADHD has never been more obviously prevalent than it is today. Affecting around 8 per cent of children and adolescents globally,² it persists into adulthood in around 43 per cent of cases,³ yielding an overall prevalence in adults of around 3 per cent.⁴ Compared with the general adult population, it is commoner in adults attending psychiatric services.⁵ Indeed, over 20 per cent of adults attending adult community mental health services in Ireland screen positive for ADHD symptoms.⁶ The research tells us that females receive their diagnoses later than males.⁷ Either way, ADHD has clearly become very common.

The research tells us that females receive their diagnoses later than males. Either way, ADHD has clearly become very common

Diagnosis

But how is ADHD defined, exactly? According to the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM-5), the core features of ADHD are inattention and/or hyperactivity/impulsivity.⁸ Inattentive criteria include (a) the display of poor listening skills, (b) losing items needed to complete tasks, (c) getting sidetracked by external, unimportant stimuli, (d) forgetting daily activities, (e) a diminished attention span, (f) an attenuated ability to follow instructions or complete schoolwork or assignments, (g) difficulty beginning tasks that require concentration, and (h) failing to focus on details leading to thoughtless mistakes in assignments. Hyperactive symptoms include (a) squirming when seated, or fidgeting with hands or feet, (b) marked restlessness that is hard to control, (c) appearing often ‘on the go’, (d) the inability to play or partake in leisure activities in a quiet manner, (e) the inability to remain seated in class, and (f) overtalkativeness. Impulsive symptoms include (a) difficulty awaiting one’s turn, (b) interrupting or intruding in the conversations or activities of others, and (c) blurting out answers before the question is finished. These two sets of symptoms make up the hyperactivity-impulsivity criteria.

Based on the aforementioned criteria, ADHD can be combined type, predominantly inattentive type, or predominantly hyperactive/impulsive type based on which sets of criteria are reached. To do so, patients must have mild, moderate, or severe symptoms or behaviours persisting for more than six months in two or more settings (for example, school, home, church, social interaction, financial skills, or driving behaviours), and which have negatively impacted academic, social and/or occupational functioning. Diagnosis requires six or more symptoms in children under 17 years, and five or more in people 17 or over. Symptoms must have been present prior to the age of 12, must not be better accounted for by another diagnosis (such as mood, anxiety, or psychotic disorders), and must not be an exclusive manifestation of oppositional behaviour.

Any reliable diagnosis is naturally based on a very thorough history that involves good quality collateral history from parents, teachers, and others who may have observed the features of ADHD.⁹ In line with the HSE’s Model of Care for ADHD,⁶ the clinical pathway for those who require assessment involves GP referral to the local child and adolescent or adult community mental health team, or mental health intellectual disability service, depending on which is appropriate.¹⁰ Even the Model of Care document itself highlights a dearth of such services, however. There are, of course, various private services offering ADHD assessment and treatment. After screening with tools such as the self-report Adult ADHD Self-Report Scale and Wender Utah Rating Scale, services typically use inventories such as the Diagnostic Interview for Adult ADHD based on DSM-5 criteria when making a diagnosis.¹¹

Clinical findings are not always negative. In one study, 93 per cent of the surveyed experts identified in their patients positive personal attributes such as energy, flexibility, resilience, perseverance, creativity, ability to inspire and energise those around them, and a general optimistic attitude.¹² Individuals with ADHD, according to the authors, were fast learners, thinkers and decision makers, and were less afraid to take risks. A subsequent study described people with ADHD possessing attributes such as agreeableness and a willingness to work with others.¹³

Still, a qualitative Irish study highlighted the importance of practitioners being aware of the impact of ADHD on adult’s lives and the associated stigma.¹⁴ A subsequent Irish study investigated the impact a diagnosis of ADHD has on the perception and experience of social inclusion among university students.¹⁵ Feelings of social exclusion were associated with negative attitudes towards ADHD, misinformation and a lack of information, and barriers to effective healthcare. Indeed, internalised stigma and anticipated discrimination among adults with ADHD appears to be the norm.¹⁶

It is not unusual for ADHD in adults to be misdiagnosed as atypical depression, a mixed affective disorder, cyclothymia, or emotionally unstable personality disorder. This might result from prominent mood lability in adults with ADHD and a subtler expression of hyperactivity and impulsivity in adults than in children. Comorbidity with other illnesses or substance use disorders is also common, which can contribute to this diagnostic overshadowing. Therefore, to address the core symptoms of ADHD and to help with associated functional impairment, treatment should involve a multimodal approach with a combination of pharmacological and psychosocial interventions.

Pharmacological interventions

Guidance from the UK National Institute of Health and Care Excellence (NICE) recommends pharmacotherapy as a first-line treatment for adults with ADHD who experience significant impairment in functioning in at least one domain of life despite environmental modifications (such as reducing distractions, changes to lighting or noise, and so forth).¹⁷ Pharmacotherapy should only be initiated by healthcare professionals who are experts trained in diagnosing and managing ADHD. Stimulant medications sometimes used as first-line treatment of adults include lisdexamfetamine and methylphenidate. These are Schedule 2 controlled drugs. If a six-week trial of one stimulant medication yields inadequate results, switching to the other stimulant option can be considered. Non-stimulant medications include the selective noradrenaline reuptake inhibitor atomoxetine. It can be useful where stimulant medications are not tolerated or where ADHD symptoms have not responded to separate six-week trials of both stimulants individually. A fourth option with scarcer evidence is the alpha-2-adrenergic agonist guanfacine.

Assessment and monitoring are particularly important, starting with an in-depth discussion with the patient about the treatment options and potential side-effects. A review of physical health and any current medications, and a risk assessment for substance misuse are all essential before prescribing ADHD medication. The health assessment includes (but is not limited to) heart rate, blood pressure, height and weight measurements, and cardiovascular examination. An ECG is not strictly required prior to prescribing ADHD medication unless cardiac risk factors are evident on assessment, however a cardiology opinion is usually advisable if there is family history of sudden death in a first-degree relative under 40 years of age, a history of congenital heart disease, a history of previous cardiac surgery, a history of exercise syncope, or evidence of shortness of breath on exertion, palpitations, chest pain, signs of heart failure, or a murmur on auscultation. Once the specialist team has established the ADHD medication and provided what psychosocial interventions it has available, an annual specialist review will usually suffice.

Non-pharmacological interventions

Non-pharmacological interventions for adults include ADHD-specific cognitive behavioural therapy, task-focused occupational therapy and ADHD-specific coaching, according to the HSE Model of Care. Other supports available include not-for-profit organisations such as ADHD Ireland who provide up-to-date information, resources, and community building opportunities for individuals with ADHD. It runs support groups for adults both online and in person. For example, it runs the Understanding and Managing Adult ADHD Programme in which adults can participate without a referral – both people with formally-diagnosed ADHD and those awaiting diagnosis.¹⁸

Finally, the HSE ADHD in Adults National Clinical Programme in partnership with ADHD Ireland and University College Dublin School of Psychology have jointly produced the Adult ADHD smartphone app for people with ADHD. The app provides self-care and signposting information regarding adult ADHD and is available at https://adhdireland.ie/adult-adhd-app/.

All of the above resources are designed to help individuals manage their ADHD and get the most out of life.

References

1. Riordan R. Percy Jackson and the Sea of Monsters. London: Puffin; 2007. p8
2. Ayano G, Demelash S, Gizachew Y, Tsegay L, Alati R. The global prevalence of attention deficit hyperactivity disorder in children and adolescents: An umbrella review of meta-analyses. J Affect Disord. 2023;339:860-866
3. Di Lorenzo R, Balducci J, Poppi C, Arcolin E, Cutino A, Ferri P, et al. Children and adolescents with ADHD followed up to adulthood: A systematic review of long-term outcomes. Acta Neuropsychiatr. 2021;33(6):283-298
4. Ayano G, Tsegay L, Gizachew Y, Necho M, Yohannes K, Abraha M, et al. Prevalence of attention deficit hyperactivity disorder in adults: Umbrella review of evidence generated across the globe. Psychiatry Res. 2023;328:115449
5. Gerhand S, Saville CWN. ADHD prevalence in the psychiatric population. Int J Psychiatry Clin Pract. 2022;26(2):165-177
6. Health Service Executive. ADHD in Adults National Clinical Programme: Model of Care for Ireland. Dublin: Health Service Executive; 2021
7. Martin J. Why are females less likely to be diagnosed with ADHD in childhood than males? Lancet Psychiatry. 2024;11(4):303-310
8. American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Washington, DC: American Psychiatric Association; 2013
9. Semple D, Smyth R. Oxford handbook of psychiatry. 4th ed. Oxford: Oxford University Press; 2019
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11. DIVA Foundation. About DIVA-5 [Internet]. Amsterdam: DIVA Foundation; [cited 2026 Oct 5]. Available at: www.divacenter.eu/diva-5/about-diva-5/
12. De Schipper E, Mahdi S, Coghill D, et al. Towards an ICF core set for ADHD: A worldwide expert survey on ability and disability. Eur Child Adolesc Psychiatry. 2015;24:1509-1521
13. Mahdi S, Viljoen M, Massuti R, et al. An international qualitative study of ability and disability in ADHD using the WHO-ICF framework. Eur Child Adolesc Psychiatry. 2017;26:1219-1231
14. Watters C, Adamis D, McNicholas F, Gavin B. The impact of attention deficit hyperactivity disorder (ADHD) in adulthood: A qualitative study. Ir J Psychol Med. 2018;35(3):173-179.
15. Smith S, McVeigh J. Perceptions of stigma and social inclusion amongst a sample of university students with ADHD in Ireland. Disabilities. 2025;5(1):24
16. Masuch TV, Bea M, Alm B, Deibler P, Sobanski E. Internalized stigma, anticipated discrimination and perceived public stigma in adults with ADHD. Atten Defic Hyperact Disord. 2019;11:211-220
17. National Institute for Health and Care Excellence. Attention deficit hyperactivity disorder: Diagnosis and management (NG87) [Internet]. London: NICE; 2018 [cited 2026 Oct 7]. Available at: https://www.nice.org.uk/guidance/ng87
18. ADHD Ireland. Who we are; Understanding and Managing Adult ADHD Programme (UMAAP); Adult ADHD App [Internet]. Dublin: ADHD Ireland; [cited 2026 Oct 7]. Available at: https://adhdireland.ie/