The Age of Diagnosis by Suzanne O’Sullivan review – are we really getting sicker?
Suzanne O’Sullivan’s new book, The Age of Diagnosis, argues that modern medicine’s expanding diagnostic net may be labeling normal variation as disease. Using Lyme disease, autism and ADHD as case studies, she warns that overdiagnosis can cause unnecessary treatment, anxiety and social stigma.
In her latest work, The Age of Diagnosis, neurologist Suzanne O’Sullivan contends that the surge in medical labels does not reflect a sicker population but a widening of what counts as illness. From the early mystery of Lyme disease in Connecticut to the modern explosion of autism and attention‑deficit diagnoses, O’Sullivan illustrates how ever‑more sensitive tests and broader criteria can turn ordinary differences into medical problems.
How Lyme disease became a cautionary tale
In the 1970s, residents of Lyme, Connecticut, complained of flu‑like fatigue, rashes and joint pain. Doctors dismissed the complaints as psychosomatic because no clear cause could be identified. A state health investigation in 1975, prompted by unusually high rates of juvenile arthritis, eventually uncovered a spiral‑shaped bacterium in deer ticks and in the blood of affected patients. By 1982 the link between the tick‑borne bacterium and the syndrome now known as Lyme disease was established.
Today two laboratory tests exist for Lyme disease, and most patients improve with a short course of antibiotics. Yet O’Sullivan points out that a test alone cannot confirm or exclude the disease. Overly sensitive assays generate false positives, while poorly calibrated ones miss genuine cases. A reliable diagnosis still depends on a clinician’s assessment of pre‑test probability—considering exposure history, symptom pattern and regional tick prevalence. The Lyme story shows that even with a clear pathogen, diagnosis remains partly an art.
When diagnostic labels outpace evidence
O’Sullivan argues that the same pattern repeats across a range of conditions. In Australia, for example, half a million people claim to have Lyme disease despite the absence of the tick species that carries the bacterium. Global estimates suggest an 85 % overdiagnosis rate for the illness.
Autism provides another striking example. Fifty years ago, prevalence was estimated at four per 10,000 children. Recent figures place it at roughly one in 100 worldwide, and in the UK diagnoses rose 787 % between 1998 and 2018. ADHD, first described in 1987 as a childhood disorder, has seen diagnoses double in boys and triple in girls from 2000 to 2018, and the label now extends to many adults.
These jumps may not signal a true rise in disease but rather a phenomenon O’Sullivan calls “diagnosis creep.” Normal behavioural variation and mild symptoms are increasingly pathologised, creating a perception that society is getting sicker when, in fact, the diagnostic net has simply widened.
Genetic testing and the burden of risk
Advances in gene sequencing add another layer of complexity. People who discover they carry mutations—such as BRCA1/2 variants that raise breast‑cancer risk to 40‑85 %—must decide whether to undergo preventive surgery or live with uncertainty. Newborn screening programmes aim to detect serious conditions before symptoms appear, but they also risk labeling infants with untreatable or low‑penetrance disorders, potentially causing lifelong anxiety.
O’Sullivan notes that screening for childhood‑onset genetic diseases is now limited to conditions where early intervention clearly improves outcomes. The goal is empowerment, not a deterministic fate. Nevertheless, the line between useful early detection and harmful over‑labeling remains blurry.
ADHD, autism and the human cost of labels
When diagnostic criteria expand, the social consequences can be severe. The Diagnostic and Statistical Manual of Mental Disorders (DSM) originally described ADHD as a condition that resolved in adolescence. The 1980 edition introduced “attention‑deficit disorder,” extending the label to older age groups. Today, many adults identify strongly with the ADHD label, and the diagnosis often shapes personal identity.
O’Sullivan’s interviews reveal a troubling gap: many diagnosed individuals report no tangible improvement in quality of life. Some have dropped out of work or education, and social relationships suffer. The perceived benefit of a label—access to medication, accommodations, or validation—does not always translate into real‑world gains.
What clinicians and patients can do
The book’s central warning is simple: physicians must remember the oath to “do no harm.” Before ordering the latest test or applying a new diagnostic category, doctors should listen carefully, weigh the evidence, and consider potential downstream effects. Patients, too, need realistic expectations; medicine cannot fix every behavioural or social issue, and not every label leads to better health.
In an era where technology can detect ever‑smaller biological signals, O’Sullivan urges a balanced approach—one that values clinical judgment, patient narratives, and the humility to acknowledge uncertainty.
Why it matters
Overdiagnosis can lead to unnecessary treatment, anxiety, and societal stigma, making it crucial to balance medical enthusiasm with careful clinical judgment.
Key points
- Lyme disease illustrates how even clear pathogens require nuanced clinical judgment
- Autism and ADHD diagnoses have surged, often reflecting broader diagnostic criteria rather than true prevalence
- Genetic testing can create dilemmas about preventive interventions without clear benefit
- Overdiagnosis may harm individuals by pathologising normal variation
- Clinicians should prioritize listening and weighing harms before embracing new tests
Frequently asked questions
What is "diagnosis creep" according to Suzanne O’Sullivan?
Diagnosis creep refers to the expanding tendency to label increasingly mild or normal variations as medical disorders, inflating disease prevalence without corresponding health benefits.
Why does O’Sullivan caution against widespread genetic screening?
She warns that identifying risk genes without effective preventive options can cause anxiety and lead to invasive decisions, such as unnecessary surgeries.
How have ADHD diagnostic criteria changed over time?
Originally a childhood condition that resolved in adolescence, ADHD criteria were broadened in the 1980s to include older children and adults, making the label a lifelong identity for many.
