Few British growth industries have been more successful than the treatment of patients with ADHD. Cases of attention deficit hyperactivity disorder, as it is properly known, are booming.

A staggering 20,000 people a month are referred for assessments for this fast-growing form of mental disability, which is said to involve restlessness, difficulties concentrating and impulsive behaviour.

Yet with predicted waiting lists for diagnosis and treatment stretching to ten years in some parts of the country, few pretend the situation is a happy one – or that we can afford it.

Health Secretary Wes Streeting has admitted that the NHS cannot cope with an epidemic that is fast becoming a crisis.

Yet not everyone is suffering. Faced with a huge growth in demand, health service chiefs have resorted to paying for tens of thousands of patients be assessed and treated privately at vast expense. And in the process they are blowing an ever-bigger hole in the cash-strapped NHS budget. In some cases, up to one pound in every three spent by the taxpayer leaks out in private profit. Real-term spending on disability benefits primarily related to ADHD has tripled between 2020/21 and 2024/25, from £193 million to £577 million.

Dr Phil Anderton is among those private operators who seem to have done rather well from this profitable industry. The 62-year-old has been hailed for ‘revolutionising’ care for sufferers. Anderton was described in one online hagiography as a ‘visionary’ who ‘doesn’t just think outside the box, but has completely reinvented it’. In another, he was said to be ‘passionate’ about ‘transforming’ the lives of his patients.

The clinic he established, ADHD360 – said to be the largest of its kind in Europe – has helped tens of thousands of sufferers since it started work in 2018. And the rewards have flowed. Dr Anderton and his wife, Samantha, 56, earned an estimated £15 million when they sold the clinic to a private equity-backed firm last year.

The registered address for his new business venture, Anderton Aviation and ADHD Ltd, is a sprawling four-bedroom country pile on the edge of a picturesque village in Lincolnshire, complete with hot tub and fire pit. Anderton has also posted photos of an Aston Martin with a personalised number plate on what appears to be his Instagram account.

This is not to say their work has not been valuable. ADHD can be crippling. When unsupported, the neurodevelopmental disorder can be ‘a potent route into educational failure, long-term unemployment, crime, substance misuse, mental ill health and suicide,’ according to the NHS. Research suggests that early intervention could save the taxpayer billions across health, education and criminal justice – but right now, it doesn’t feel quite that way as the health service struggles to pay for an ADHD crisis spinning out of control.

With an estimated 700,000 people in England on waiting lists for assessments, GPs can speed up the process by referring patients to private clinics, with the NHS footing the bill. With as many as half of the NHS’s assessments carried out privately, it is estimated to have paid £128 million to independent clinics last year, up from £36 million two years ago.

Revenues are booming. Turnover at ADHD360 increased by more than 80 per cent to £22.5 million in 2024, its latest figures show.

Gross profits were up to £9.7 million at a margin of 43 per cent, with pre-tax profits rising to more than £2 million.

In an interview with a trade magazine, Dr Anderton – whose PhD is in ‘workforce appraisal and competence measurement’ – acknowledged that the balance sheet matters but insisted that helping people improve their lives was more important.

Yet job adverts for ‘patient success advisers’ at ADHD360 describe how employees are expected to ‘upsell treatment plans’ and ‘discuss benefits of our patient proposition and convert into patient commitment by securing payment for assessments’.

ADHD360’s ‘essential care package’ of an assessment via video call and treatment has an upfront cost of £1,740, while its ‘comprehensive care package’, which offers a priority assessment and ‘enhanced care’, is priced at £2,850. Sales reps must also hit daily targets for making calls to potential new patients, the job adverts state. It is likely that these packages relate to private clients, not those referred to the clinic via the NHS. Regardless, some might ask if this reflects an ethos that always puts patients above profits.

This is not the sort of challenging question that Dr Anderton is prepared to answer. He terminated an interview with The Mail on Sunday after he was asked about a 2023 BBC Panorama investigation, which highlighted concerns about the quality of ADHD assessments carried out at private clinics, including ADHD360.

As part of the BBC investigation, an undercover reporter was diagnosed with ADHD and offered powerful drugs after flawed assessments at three private clinics. An earlier, rigorous assessment by an NHS consultant psychiatrist concluded that he did not have the condition. The reporter said he chose to investigate ADHD360 after patients and former staff had told him that appointments were short and almost everyone received a diagnosis.

Last week, ADHD360 was at the centre of controversy when a patient it had diagnosed as having the condition was told she could win a payout as high as £126,000 because her employer, Avon & Somerset Constabulary had failed to provide a set of noise-cancelling headphones to help her concentrate – even though she had a suitable pair at home.

ADHD360 found Donna Vale had the condition after an online consultation, even though her own GP thought her symptoms were down to ‘low self-esteem’. Her line manager questioned the diagnosis, for which Ms Vale won a claim of disability harassment against the force.

In its response to the Panorama allegations, ADHD360 said it is regulated as an NHS provider and that its ‘qualified clinicians’ deliver ‘high standard assessments, diagnosis, treatment and care’. It added that on this occasion its ‘prescription policy was regrettably not followed’ and procedures had been reviewed.

ADHD360 is one of three clinics to have been snapped up by private equity-backed firms in recent years. Between them, they reported more than £30 million in gross profit in their latest accounts. David Rowland, director of think-tank the Centre for Health and the Public Interest (CHPI), says ADHD clinics are proving popular with private equity firms because they represent an ‘opportunity to make quick profits’.

‘Historically, when private equity gets involved in the NHS this can mean large sums of taxpayer money is sucked out of the service to provide high rates of return for investors,’ he added.

Psicon, which was set up in 1998 by South African L.J. Conradie, a former NHS neuropsychologist, says it provides ‘a warm and welcoming safe space, where every troubled, “different”, unhappy or challenged individual feels understood and hopeful for their future’.

In 2023, it was sold for £33.2 million to OneBright, a healthcare group backed by private equity firm EMK Capital. The sale resulted in a bumper payday for the Conradie family, who netted around £20 million for the transfer of their shares in the company. Mr Conradie is now retired.

Psicon made net profits of almost £6 million in 2024, paid out £4.6 million in dividends to shareholders and a salary of almost £300,000 to its managing director.

A Psicon spokesman said the firm has ‘a long-standing record of working successfully with the NHS under formal contractual frameworks’ set by the NHS and was ‘proud’ to have helped reduce waiting times.

He added: ‘All providers with qualifying NHS contracts are obliged to accept patients on to their waiting lists if they meet the clinical criteria specified in that contract. We ensure we deliver care in line with the standards and costs set out by the NHS and always use public resources responsibly.’

Private clinics say they are alleviating the burden from the NHS, bringing down unacceptably long waiting times and providing more cost-effective services. They also point out that it is the NHS that dictates commercial terms, including tariffs and standards, not the providers.

An ADHD diagnosis is commonly followed by prescriptions for powerful stimulants. The most famous brand name is Ritalin.

While more than 800,000 people in the UK have a formal diagnosis, an estimated 2.6 million have the condition. And with more than 325,000 adults and children now taking ADHD medication – more than double the number in 2018/19 – it has become an increasingly contentious field. So, is this a mental health crisis or a business opportunity? And how is any of this sustainable for the taxpayer?

Some experts are convinced that ADHD is now being over-diagnosed. Sir Simon Wessely, former president of the Royal College of Psychiatrists, has warned that some private clinics ‘do not have the standards that we would expect and seem to make the diagnosis incredibly easy’.

He also cited ‘cultural and social factors’. Recently, a raft of celebrities have ‘come out’ as having ADHD, including director Greta Gerwig, reality TV star Sam Thompson and TV host Sue Perkins. Discussion about ADHD is rife on social media, with #ADHD attracting more than 20 billion hits on TikTok alone.

Joanna Moncrieff, a consultant psychiatrist and professor at University College London, says subjective diagnostic criteria are muddying the waters. Moncrieff, who conducts ADHD assessments at an NHS clinic, says many consultants are ‘really uneasy’ with the spike in diagnoses and ‘feel that they’re being asked to treat people who don’t have very significant problems’.

She believes some clinics are ‘cashing in on a social phenomenon… and, by doing that, helping to drive the whole phenomenon’.

There is no suggestion that her comments, or those of Sir Simon Wessely, refer to any of the clinics named in this article.

It seems some of the bigger firms are well aware of the need to promote their wares more effectively. For example, the MoS has found that ADHD doctors are accepting payments from drug manufacturers in a move critics fear could be fuelling over-prescriptions. Two leading ADHD specialists, who run their own private clinics, have accepted more than £200,000 from drug firms since 2022, according to analysis of data compiled by the Association of the British Pharmaceutical Industry.

The data entries – made by the pharmaceutical firms – do not detail exactly what the payments are for, but they often remunerate experts for their time on advisory boards or to attend medical conferences. This is within the rules, but critics say there is evidence that the cash affects prescribing habits, fostering a ‘drugs-first mentality’.

What no one disputes about the ADHD boom is that it cannot go on like this. NHS spending on the condition is set to reach £314 million this year, more than double the year’s £150 million ADHD budget. That means other services could face cuts to offset the £164 million overspend.

Rowland, of the CHPI, is calling for a cap on the profits of private companies delivering NHS care.

An increase in autism and ADHD diagnoses has fuelled a surge in spending on pupils with special educational needs and disabilities, which has increased by two-thirds since 2012/13 to hit £11.1 billion this year. Eight in ten local authorities have said they face insolvency over the mounting costs.

In a study by the Centre for Social Justice, charities reported that parents were putting their children through ADHD assessments knowing they would receive additional benefits if diagnosed.

One charity worker told the think-tank that getting a diagnosis was a ‘golden ticket’ to extra cash, which can amount to more than £25,000 a year.

In the meantime, the system is failing those who need it most. Waiting times can now stretch to a decade, while some have had to ration their medication because of the costs involved. Private clinics have even taken to offering buy now, pay later services.

All the while, the tax bill continues to climb, even if one enterprising corner of British commerce is in the rudest of good health.

• Additional reporting: Rhodri Morgan