The Age of Diagnosis

'The neurologist takes eloquent aim at a medical culture that, although well intentioned, is too quick to assign clinical labels to aspects of the human condition... A brave and compassionate book.'

Financial Times, best summer books of 2025

How does she carry off that high wire act, being so technical and expert and grounded in data, while telling stories in a way that makes them utterly addictive? I love the way she listens to people talking. It's a really important, intelligent, compassionate and brave book, and it speaks very eloquently to things happening in our ideas about ourselves.

Tessa Hadley

A humane and thoughtful observer of the oddities of the human mind... full of intriguing case studies and wise observations. Her new book ranges widely, taking in the drawbacks of mass screening for illnesses as well as the perils of overextending mental health categories... We make people sicker by by the simple act of diagnosing them with a medical problem. A fascinating book.

The Times

A brave and deeply compassionate book with a very important message.

Henry Marsh

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

In my view the best science writer around - a true descendant of Oliver Sacks.

Sathnam Sanghera

Two elegant offerings from neurologists stand out for using patient stories to tell us something about ourselves. Suzanne O'Sullivan courageously questions medicine's well-intentioned enthusiasm for attaching labels - think ADHD, anxiety - to aspects of the human condition. This is sensitive political territory, given the public conversation about the 2.8m people who are economically inactive due to long-term illness, but it deserves a hearing.

Guardian, Best Books of 2025

'In my view, the best read of the summer is not wrapped around by a pastel drawing of Adirondack chairs bathed in sunlight. Instead, the cover shows one of those extra strong paper labels you get to wear like a bracelet to identify you and what ails you when you're in hospital. That's by way of a clue to the fact that this book, The Age of Diagnosis by Dublin-born neurophysiologist Dr Suzanne O'Sullivan, is all about what ails you now, may ail you in the future, could put you off your oats, into hospital or, if you get seriously unlucky, kill you less pleasantly than you ever imagined...fascinating... more impelling than any thriller.'

IRISH EXAMINER

A book of great wisdom as well as compassion - the result of decades working along the frontiers of brain, mind and body. Modern medicine is powerful; with care and with stories from her clinic, Dr O'Sullivan shows just how harmful it can be too.

Gavin Francis, author of ADVENTURES IN HUMAN BEING

I loved this beautifully written and provocative book. The Age of Diagnosis asks brave and important questions, taking on the medical establishment as well as contemporary societal norms. O'Sullivan's primary motivation in her writing, her philosophy and her work as a doctor is extreme empathy and advocacy for her patients.

Christie Watson, author of THE LANGUAGE OF KINDNESS

O'Sullivan explodes conventional wisdom about medical diagnoses. She knows that having a diagnosis like austism, or ADHD, or depression, or Lyme disease, can give her patients relief at having an explanation. But she also invites us to wonder where these diagnoses came from. Are we overdiagnosing? Is this really the best strategy for helping people get better? With clarity of prose and reasoning, The Age of Diagnosis should make all of us think about whether we are more or less healthy when we receive a diagnostic label.

Elizabeth F. Loftus, Distinguished Professor, University of California, Irvine

'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