In the 14th century, King Charles VI of France suffered from a curious, but by no means original, delusion. He believed his body was made entirely of glass. A relatively new material, both fragile and transparent, glass captures the hypochondriac’s acutest fear – brittle vulnerability – with their greatest desire: visceral omniscience. This human longing to peer inside our “meaty vessel” was answered in the 20th century by medical technologies, including blood testing, microscopy and imaging, which became widely available. Rather than soothe the hypochondriacal itch, however, this intimate access – along with Google’s democratisation of medical knowledge – has fuelled health anxiety to new heights.

Caroline Crampton describes herself as a hypochondriac, but one with impostor syndrome because she previously had a severe “real” illness. She thinks back to the naivety of her 17-year-old self, unaware of “the tennis ball-sized lump” above her left collarbone that was “already big enough to cast its own shadow”. Life-threatening disease was lurking in plain sight, painfully obvious to see in old photos. More than a decade after radiotherapy, chemo, a stem cell transplant, egg retrieval and a successfully managed recurrence of Hodgkin’s lymphoma, Crampton now sees tumours everywhere. The hypochondriacal cancer survivor is, she suggests, tragicomic. A brush with malignancy is supposed to remind you what really matters; instead, Crampton feels trapped in the limbo between the “binaries of sickness and health”, poking at her body in the mirror.

With extensive experience in the worlds of the medically explained and the medically unexplained, Crampton is perfectly placed to write this fascinating and intelligent cultural history of health anxiety, suffused with the intensity of feeling that hypochondria ignites, as well as the insight that it often precludes. She is curious that hypochondria persists as a popular term, despite its vagueness and stigmatising edge. Medics don’t want to give it up either (in fact, there was a question on hypochondria in the Royal College of Psychiatrists’ membership examination just this month). While the Diagnostic and Statistical Manual of Mental Disorders, or DSM-5, an international “bible” of psychiatric conditions, has updated its terminology to “somatic symptom disorder” and “illness anxiety disorder”, messy reality strains the seams of these diagnostic categories.

Hypochondriacs tend to have a specific preoccupation – cancer, infertility, an indwelling parasite – and scan their body for evidence to support this conviction, which sets off the “falling dominos of catastrophisation”. But hypochondria also overlaps with obsessive compulsive disorder and conversion disorder (when stress or emotion manifests as pain, weakness or similar symptoms that don’t fit a pattern that can be readily explained). Crampton also experiences complex post-traumatic stress disorder from her years as a cancer patient, characterised by flashbacks, intrusive thoughts and hypervigilance. Wading through these labels, her guiding question – “Who gets to decide what is reasonable fear and what is unreasonable?” – is exactly the right one to be asking.

A Body Made of Glass does not claim that hypochondria has a redeeming edge, unlike previous books on the topic. Brian Dillon’s Tormented Hope (2009) argued that health anxiety shares a root with creative genius. Crampton intersperses sections of memoir with historical research and the lives of renowned sufferers similarly to Dillon, including Charles Darwin, Glenn Gould, Philip Larkin, Molière, Marcel Proust and John Donne, but rather than use these as evidence of hypochondria’s artistic silver lining, she finds consolation in the eloquence they bring to their health concerns. Crampton takes us back to the origins of hypochondria – named first, supposedly, by Hippocrates and evident as a concept even earlier in Egyptian texts.

Etymologically “under the sternum”, hypochondria used to be rooted firmly in the body. Humoral medicine cast the condition as an imbalance of black bile, which then became connected to the “wandering womb” of hysteria, followed by the more ethereal “vapours” in the 17th century and nerves in the 19th century. The body faded from view as hypochondria was reconceived as an illness of the mind. For more than 100 years, hypochondria has been the firm property of psychiatry, while continuing to be a lucrative target for quacks and charlatans.

How concerned the public are encouraged to be about their health depends on the historical moment. Written over five years, A Body Made of Glass is a Covid-19 book of sorts, bearing the hallmark of a time when illness became everyone’s preoccupation and the stigma of health anxiety eased (in fact, Crampton found relative calm and companionship in the pandemic, joined in her habits of self-surveillance). To consider the number of ways the human body can malfunction is dizzying; it is a miracle to be well. In a way, hypochondria makes perfect sense. We are all dying. To the hypochondriac, most of us are just too easily soothed into a state of forgetting this.

Despite being failed by doctors in a multitude of ways, Crampton has the grace to empathise with the challenge of caring for patients with hypochondria. Clinicians can feel pressurised to either double down into a position of unearned certainty that there is nothing wrong or to overinvestigate. Faced with the task of triaging potentially fatal or life-limiting illness, doctors cannot – particularly in a rationed healthcare system such as the NHS – scan, biopsy and operate on demand. An important consideration Crampton glides past is the iatrogenic harm and collateral damage that can result from chasing “incidentalomas” – chance findings that so often turn out to be benign.

Crampton rejects the convention that illness narratives should end with either tragedy or cure. She explains how antidepressants, EMDR (eye movement desensitisation and reprocessing) therapy and cognitive behavioural therapy can help some people live with health anxiety, but are not miraculous solutions. Avoiding the trap of false reassurance, however appealing for those experiencing hypochondria, she sets an example. Historically, doctors have been far more often wrong than right, and particularly ready to unhear marginalised and minoritised voices.

A Body Made of Glass strengthened my belief that clinicians would do well to share doubts with their patients, becoming allies in uncertainty rather than antagonists. Both people in the consulting room are seeking confirmation about what is going on, but must hold the disturbing truth that there is so much about our bodies we continue not to know.

Kate Womersley is a doctor and academic specialising in psychiatry. Her work at Imperial College London focuses on sex and gender equity in biomedical research

• A Body Made of Glass: A History of Hypochondria by Caroline Crampton is published by Granta (£16.99). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply