Adult attention-deficit hyperactivity disorder (ADHD) waiting lists pose a significant national problem,^{1,Reference Young, Asherson, Lloyd, Absoud, Arif and Colley2} an issue unlikely to resolve without substantial intervention. Over the past two decades, recognition^{Reference Davidovitch, Koren, Fund, Shrem and Porath3} and effective medical treatments^{Reference Childress, Komolova and Sallee4} for ADHD have markedly expanded, contributing to a consistent increase in clinical demand across the UK.^{Reference Renoux, Shin, Dell'Aniello, Fergusson and Suissa5} Notably, the consensus among authors is that the COVID-19 pandemic has further exacerbated the issue of waiting times.

During the mid-1990s, only a handful specialist adult ADHD services existed in the UK, often composed of small, resource-limited teams. These teams were tasked with addressing extensive regional clinical demands for assessments and treatments. Following the publication of the 2008 National Institute for Health and Care Excellence (NICE) guidelines, specialist services throughout England significantly increased.^{Reference Asherson, Leaver, Adamou, Arif, Askey and Butler6} Despite this growth, many regions of the UK still experience limited access to adult ADHD services.^{Reference Price, Janssens, Newlove-Delgado, Eke, Paul and Sayal7}

In addition to this, the resources allocated to these services have failed to keep pace with the ever-growing demand, resulting in lengthy waiting lists for specialist services. A 2018 Freedom of Information request to clinical commissioning groups highlighted a substantial variation in waiting times for assessment following referral, ranging from 4 weeks to nearly 4 years.¹

Statistics concerning waiting lists can be misleading. Headline figures usually consider the individual at the front of the queue. However, for an individual awaiting assessment, the estimated waiting time from their addition to the list, or the ‘back of the queue’, is more relevant. For a service that currently quotes a 2–4 year wait from referral to assessment, a more realistic estimate for a newly added individual is likely to be 5–10 years if no additional funding is provided. This figure is based on calculations done by specialist services where demand is assumed to be static and clinical teams are operating at full capacity.

Although specialist services, the medical literature,^{Reference Young, Asherson, Lloyd, Absoud, Arif and Colley2} the media^{Reference Bish8} and government⁹ increasingly recognise the widening gap between resource demand and capacity, a lack of both national strategy and political focus exacerbates this problem. The escalating problem of ADHD waiting times has continued largely unchecked owing to a lack of specific targets for these waiting times¹⁰ and the absence of routinely collected national data. This stems primarily from a lack of set targets for ADHD, as exist for other conditions, such as autism spectrum disorder.¹¹ This issue was highlighted in the government's response to a parliamentary debate held in February 2023 on ADHD waiting times.¹² The response concluded that, in the absence of a specified NICE target, local commissioning organisations, rather than central government, should resolve the problem of waiting lists.

According to the National Health Service (NHS) constitution,¹³ patients have a right to start consultant-led treatment within a maximum of 18 weeks of referral. However, the government does not consider this time frame applicable to ADHD.¹² In response to the unmet standard following the COVID-19 pandemic, NHS England outlined its strategy for increasing capacity in its Elective Recovery Plan.¹⁴ This ambitious plan aimed to eliminate waits longer than 2 years by July 2022 and waits longer than 1 year by March 2025. However, this plan mainly addresses non-urgent hospital treatment, primarily surgical, and makes no reference to mental health services.

Underfunding of NHS adult ADHD services has resulted in a significant growth of independent providers, whose numbers have increased in response to the unmet demand. The National Health Service Commissioning Board and Clinical Commissioning Groups (Responsibilities and Standing Rules) Regulations 2012,¹⁵ embedded in the NHS Constitution, grant individuals living in England the right to choose the location of their first out-patient appointment with any provider that holds an NHS-commissioned contract. In view of this, many patients have accessed ADHD services through public funding via alternative routes.

Although this increased capacity has been welcomed by many patients facing long waits, it has also introduced additional challenges into the system. The large number of providers in both the NHS and the independent sector presents a challenge to patients, clinicians and commissioners tasked with navigating a complex and fragmented system and determining the quality and reliability of these services. Although NICE provides guidance on the assessment and treatment of ADHD¹⁰ it is not specific enough on what constitutes quality assessment and treatment to ensure the required consistency between providers. Financial and human resources have been diverted from NHS services,^{Reference Ulrich16} and duplication and wastage have resulted from NHS services needing to reassess people diagnosed elsewhere when there is a lack of confidence in assessments. Furthermore, many patients have been left without medication when their general practitioner (GP) has felt unable to continue ADHD medication under shared care arrangements because of a lack of confidence in the diagnosis. The General Medical Council¹⁷ places a clear responsibility on prescribers to prescribe medicine only where ‘you have adequate knowledge of the patient's health and are satisfied that the medicine or treatment serve the patient's needs’. These issues have recently been the focus of significant media attention following a BBC Panorama documentary.¹⁸

The extraordinarily long waiting times for ADHD services are particularly alarming given the effectiveness of treatments for this condition. Stimulant medications used for ADHD, which have one of the largest effect sizes in psychiatry,^{Reference Surman, Hammerness, Pion and Faraone19} improve both symptom control and functional impairment,^{Reference Coghill, Banaschewski, Soutullo, Cottingham and Zuddas20} and are generally safe and well tolerated.^{Reference Cortese, Adamo, Del Giovane, Mohr-Jensen, Hayes and Carucci21} Moreover, the need for timely treatment is underscored by the range of negative outcomes for individuals with the condition, including accidents/unintentional injuries,^{Reference Libutzki, Neukirch, Kittel-Schneider, Reif and Hartman22} comorbidity,^{Reference Choi, Woo, Wang, Lim and Bahk23} increased mortality^{Reference Dalsgaard, Østergaard, Leckman, Mortensen and Pedersen24} and suicide.^{Reference Balazs and Kereszteny25} In addition, there is a financial cost to the individual,^{Reference Daley, Jacobsen, Lange, Sørensen and Walldorf26} their family and the wider public ^{Reference Vibert27} resulting from delayed access to treatment.

The human and financial costs of untreated ADHD represent a compelling case for investment in this area, considering that effective long-term management benefits both the individual and the wider economy. The impact of unaddressed ADHD reverberates across the broader system, affecting areas such as social care,^{Reference Biederman and Faraone28} health and the criminal justice system.^{Reference Gudjonsson, Fridrik, Susan and Kristin29}

ADHD in adults is a chronic condition with a substantial cost to society, requiring sustained and targeted investment to support those affected. Existing approaches to funding and delivery of services in the UK have been largely insufficient, as evidenced by the current state of the NHS services.

In conclusion, the crisis in adult ADHD services is an opportunity to rethink how these services are procured and delivered. The shortcomings of the current system highlight the need for investment, but more than that, they underscore the need for a different approach to service delivery.