Back in late 2025, when Keir Starmer’s grip on the Labour party was loosening and Reform UK was still in its pomp, the then health secretary, Wes Streeting, commissioned what the government called its “Independent review into prevalence and support for mental health conditions, ADHD and autism”.

Here, it seemed, was not just an inquiry into England’s ever-extending waiting lists for the diagnosis of mental illness and neurodevelopmental conditions, and the dire lack of support for people who experience one or both of them. The review would also dovetail with two other huge issues: mounting claims of “overdiagnosis”, which Streeting had appeared to partly endorse, and the government’s drive for the reform of so-called welfare. An apparently well-briefed piece in the Times seemed to speak volumes: work led by the renowned psychologist Peter Fonagy, it said, was commencing just “as Labour seeks a fresh crackdown on welfare spending” amid diagnoses “which have become the most common reason for a sickness benefit claim”.

Last Friday saw the publication of the 600-page final report Fonagy had co-authored with Gillian Baird – a specialist in paediatric neurodisability – and the psychiatrist Simon Wessely. And, as so often happens with such inquiries, its interpretation suggested the media’s equivalent of a Rorschach blot. One of the Guardian’s headlines was “No ‘snowflakes’: mental health review says today’s youth have it harder and harms are real”. The Mail, by contrast, yelled out a rather different message – “Rush to diagnose ADHD and autism can damage children” – while the Telegraph went for “ADHD surge fuelled by benefits, report warns”.

Such are the perils of producing a very nuanced mixture of analysis and recommendations. When he appeared on Radio 4’s Today programme, Fonagy said that Streeting had been “completely wrong” to agree with suggestions of the common overdiagnosis of mental health disorders. When it comes to autism and ADHD, he and his colleagues’ report says that “if present trends continue we are clearly entering a phase in which the balance of risks is changing, from previous merited concerns with under-recognition and underdiagnosis towards an increased risk of misdiagnosis and overdiagnosis”.

But it also insists that right now, “we cannot conclude that overdiagnosis is occurring at scale”, and points out that any data that might settle this festering argument “largely do not exist”. This is not the kind of stuff that suits a world that craves simple binaries and polarised shouting, but it speaks an undeniable truth.

For the most part, in fact, it is hard to disagree with what the review points out. But among its conclusions lies one troubling proposal – that provision for both mental illness and so-called neurodivergence can and should often be led by observations of need rather than formal diagnosis. In making that suggestion, I have no doubt that Fonagy and his colleagues’ intentions are benign. But our systems of power and politics and the government’s increasingly anxious view of public spending could yet make it very dangerous indeed.

First, though, the undeniable positives. In a very elegantly written and often moving introduction, Fonagy – who is 74 – completely rejects the popular idea of a new generation of wilting wimps falsely claiming to be suffering from mental ill-health. “The cacophony of voices now available to a young person – most of them digital, many of them confident, few of them accountable – has made the ordinary developmental process of understanding oneself far harder than it was for me,” he says.

He goes on: “Young people today are contending with more powerful forces than I ever faced. They are not fragile. They are outnumbered.”These are mental health issues. When it comes to autism and ADHD, Fonagy and his two colleagues’ insistence that overdiagnosis is currently not happening “at scale” and that “the evidence does not show that people presenting today are less impaired than those presenting previously” is very important indeed. When Streeting commissioned the review, among the most in-vogue books was The Age of Diagnosis by the neurologist and epilepsy specialist Suzanne O’Sullivan, which made the absurd suggestion that the overdiagnosis of autism might have reached the point where it was partly to blame for rising rates of anxiety and depression among the young, linked to her claim that “the stigma of autism has been associated with low self esteem among children”. (If autism is still stigmatised, O’Sullivan publicly calling it an “illness” is hardly helpful.)

The review, by contrast, is altogether more calm and evidence-based: for a bundle of reasons, it says that overdiagnosis and misdiagnosis may well be a future risk, but we can guard against those dangers by more closely regulating private diagnostic clinics (which are often partly NHS-funded) and stop them advertising their services. These are proposals that many autism and ADHD insiders agree with.

On a different subject, Fonagy and his co-authors also do us all a favour by emphasising the correct meaning of the ubiquitous term “neurodiversity”: whereas O’Sullivan says that it “has a biologising, pathologising effect”, the report rightly understands that the word means the complete opposite: it crystallises the plain fact that “variation in brain function, cognition and behaviour is part of natural human diversity rather than pathology or disorder”.

But what do we do when faced with genuinely diagnosable conditions that are debilitating and entail intensive support? One bit of first-person testimony in the report is heartbreaking. “When she was 12,” says an unnamed parent, “our daughter was put on ADHD medication, which lowered her mood, leading her to self-harm. She was referred to CAMHS [child and adolescent mental health services] who turned her down. Within the next month we ended up in A&E due to taking an overdose. She was then finally accepted by CAMHS, who suggested an autism assessment.

“Two years later, after receiving an autism diagnosis, little changed. School would not make any adjustments until an EHCP (education, health and care plan) was accepted, and social care said she did not meet their threshold for support because she did not have a learning disability. Our daughter was broken and unsupported and was admitted to inpatients at 15 years old.”Herein lies one of the review’s few dangers. By way of lessening an increasingly frightening crisis that is partly centred on pitifully long waits for formal diagnoses that can easily be ignored, it suggests moving towards a more “needs-based” approach, which echoes the government’s plans for special needs education.

“There should be a fundamental shift from a diagnosis-dependent system to a needs-led plus diagnosis system,” it says. Such a change, the report says, would require “increased capacity, transformation through digitally enabled care, clearer national standards and sustained investment”.

They are my italics, with very good reason. The government responded to the report by saying that the health and social care secretary, Yvette Cooper, “has asked NHS leaders to urgently examine how people can access advice, assessments and treatment more easily”. But without sufficient money, “needs-based” help is likely to amount to very little at all. Coincidentally, the Fonagy review arrived on the same day as reports that the prime minister and the chancellor had rebuffed Cooper’s requests for money to fund a pay rise for NHS staff including nurses, porters and midwives. So what chance of a huge cash injection to tackle what the report so starkly highlights?

Meanwhile, the Department for Work and Pensions still has a culture built around crackdowns and pushing people into work. Councils repeatedly fail to meet their responsibilities for the care and education of neurodivergent people. And, in the absence of properly funded change, both they and people suffering mental illness only stand even a faint chance of pushing their way through an almost impossible mess of bureaucracy and obstruction if they have pieces of paper confirming that their condition – or conditions – are real and true.

This is what makes politicians who talk of “overdiagnosis” look so crass, and the likely fate of such a definitive and in-depth report so tragic. It is an all too familiar story, indicative of our current defining national predicament: the government simply cannot afford what it proposes, so one of our cruellest modern crises looks set to grind on. John Harris is a Guardian columnist