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?

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.