From autism to allergies, ADHD to long Covid, more people are being labelled with medical conditions than ever before. But can a diagnosis do us more harm than good?
A BEST BOOK OF 2025 IN THE TIMES, GUARDIAN, LONDON STANDARD, NEW STATESMAN AND IRISH TIMES

'Covers so many topics that have been troubling me but I hadn't been able to resolve myself - as a parent and a clinician. An absolutely absorbing read from start to finish.' - CHRIS VAN TULLEKEN

'A brilliant study of the dangers of overdiagnosis' - GUARDIAN

'Compassionate and bracingly independent thinking' - THE TIMES

The boundaries between sickness and health are being redrawn.

Mental health categories are shifting and expanding all the time, radically altering what we consider to be 'normal'.

Genetic tests can now detect pathologies decades before people experience symptoms, and sometimes before they're even born.

And increased health screening draws more and more people into believing they are unwell.

An accurate diagnosis can bring greater understanding and of course improved treatment. But many diagnoses aren't as definitive as we think. And in some cases they risk turning healthy people into patients.

Drawing on the stories of real people, as well as decades of clinical practice and the latest medical research, Dr Suzanne O'Sullivan overturns long held assumptions and reframes how we think about illness and health.

"'Exceptional... Chapter by brilliant chapter, [The Age of Diagnosis] raises fundamental questions we should all be asking when thinking about illness, be it cancer or genetic disorders, never shying away from difficult truths.'" - New Statesman

"These are incredibly difficult areas to explore...O'Sullivan is brave to take this subject on, and she hits the target... O'Sullivan is an excellent, fluid writer, and an eloquent speaker... In a world where medical misinformation and disinformation flourish, and people die as a result, it takes courage to counter them without pandering to stereotypes. But that is what The Age of Diagnosis does so well... Its overall message is clear: diagnosis is a tool to be wielded with the utmost caution, and tolerance for difference and for imperfection can go a long way in keeping us healthy." - The Guardian

"The neurologist Suzanne O'Sullivan has written insightful books about psychosomatic conditions. Here she turns her attention to the perils of over-diagnosis - including autism, allergies, ADHD and long Covid. Be prepared for compassionate and bracingly independent thinking." - The Times books to look out for in 2025

"'O'Sullivan impressively marshals evidence of how drivers of 'overmedicalisation' have arisen, the minimal benefits conferred and the harms that can result. Most striking is her examination of the explosion in diagnoses of mental health conditions, such as autism and ADHD... O'Sullivan seeks out the 'reality' behind appearances, though her scepticism is tempered with sympathy and understanding... So entrenched has overmedicalisation become that there now seems no prospect of its being reversed. O'Sullivan's masterful diagnosis of how this has come about is immensely persuasive.'" - Literary Review