Rates of diagnosis in all areas of health – mental and physical – are going up. Why? Are we that much less mentally and physically healthy than we used to be? Or is something else going on?
In her book The Age of Diagnosis, Consultant Neurologist Dr Suzanne O'Sullivan sets out to examine other possible explanations: Are we simply better at identifying the people in need of treatment? Or, are we pathologising normal differences and attributing more to sickness than we did before?
There's evidence to support both. There's no doubt that many conditions, such as autism, have been historically underdiagnosed and individuals have suffered as a result. But it's also true that many diagnoses have expanded beyond their original limits. For example, today the definition of depression in the DSM allows for a diagnosis of major depression to be made soon after a bereavement; previous versions included a 'bereavement exclusion' to take into account that feelings of severe low mood and despair may be expected in the time directly after the loss of a loved one.
One of the major difficulties we face is that many conditions and disorders exist on a spectrum of mild to severe. O'Sullivan is keen to highlight that anyone on the moderate-to-severe end of the scale would likely benefit from a diagnosis, or at least from reaching out for support. If your symptoms are on the milder side, however, a diagnosis could, ultimately, do you more harm than good. And it is rates of diagnosis within this milder range that are really increasing. Rates of diagnosed severe ADHD, for example, are relatively stable, even though there has been a 400% increase in adults seeking ADHD diagnosis between 2020 and 2023 in the UK.
O'Sullivan opens her book with an exploration of Huntington's Disease, an incurable and aggressive disease that you have a 50/50 chance of inheriting. If you do inherit it, there's no way of stopping it or reducing its severity, it is simply a matter of when the symptoms will begin to kick in. Testing is available to children (18+) of parents with HD, but only after several sessions with a genetic counsellor to really go over the consequences of knowing the result.
It's worth stopping and thinking about whether you would want to know. As a young adult, how would your life be affected by the knowledge that at some undetermined point in the not-so-distant future your health was going to suddenly and dramatically deteriorate to the point that you needed full-time care, and there was nothing you could do about it. While HD is an extreme example, and tragic for it, we know that it's difficult to answer whether or not we would want that information because we know that it would affect so much of how we see ourselves, our lives, and what we believe was available to and possible for us.
O'Sullivan argues that when diagnoses are given to people at the mild end of a condition, they risk having worse health outcomes through over-identification with their condition. And there's research to back it up. That – even if a diagnosis is correct – you will have better health outcomes if you resist making it an integral part of your identity. This is even true of physical health conditions like heart disease.
Not only is there a risk of potential harm to the individual with mild symptoms and/or traits, but also – importantly – increasing numbers of people with a certain diagnosis means fewer resources, longer queues, and less reliable and effective research, all of which ultimately negatively affects those who are in more severe need, whilst doing little for those in light need.
This debate rages fiercely amongst the public and medical professionals alike. The question raised by O'Sullivan's thoughtful and compassionate investigation that I found the most compelling however was: even if we think we could diagnose, should we? In this sense, the book is as much a philosophical meditation as a work of science writing, because it tackles a broader question about the human desire to reduce uncertainty and pursue 'progress', sometimes for progress' sake.
While subjectivity is at the core of psychological health, O'Sullivan also tackles potential problems in the diagnosis of physical health problems, including cancer. Vast improvements in predictive medicine mean that people can be warned sooner than ever about their chances of developing certain illnesses in the future. However, mortality rates aren't really changing. "The difficulty that every cancer screening programme faces is to find a balance between missing as few fast-growing cancers as possible (underdiagnosis) and avoiding detecting too many early cancer cells that were never destined to progress to cause health problems if left alone (overdiagnosis).
That most programmes err significantly on the side of overdiagnosis is demonstrated by the outcomes of numerous screening programmes. A successful screening programme should prevent late-stage cancers, cancer deaths, and overall mortality, but time and again they do not work out that way."
One of O'Sullivan's main concerns with overdiagnosis is not only that people may end up having life and body altering surgeries or treatments that they may not need, but also – as an expert in psychosomatic illness – that she is acutely aware of the mind's ability to make the body unwell. I was one of many who would have found the idea of being told an illness was psychosomatic derogatory and dismissive, until an experience of chronic lower back pain – both entirely physically unexplained and utterly physically agonising – after a heavily distressing relationship and break up forced me to confront the ways in which my mind and body interrelate.
As I write I'm in touch with how vulnerable it really is to accept this mind-body connection. Doing so goes against our very natural desire to have concrete explanations for our physical discomfort, but this is in part because the idea of psychosomatic illness is still misunderstood to mean that the individual is malingering, 'making something up' or not really suffering. The reality, as O'Sullivan points out, is very different: "Psychosomatic disorders produce real physical symptoms. Psychosomatic symptoms are genuinely experienced but are not due to a disease. A psychosomatic mechanism does not mean a person isn't disabled, only that the problem has arisen through a complex mind-body interaction rather than being due to pathology."
O'Sullivan explains some of the rejection of psychosomatic illness as being due to the fact that society has very few caring institutions other than those designed for physical ailments, meaning that physical symptoms are always prioritised. O'Sullivan reflects on the Covid-19 pandemic as a time that most people had reduced access even to these facilities, and wonders – backed up by research evidence, as always throughout the book – whether the prevalence of people diagnosing with long Covid can be explained in part by the difficulty of being isolated and alone with unexplained symptoms and nowhere to find reassurance: "Without long Covid, many of those feeling the social and psychological effect of the pandemic had no voice." The fact that long Covid entered the public and then medical mainstream without sufficient examination after being conceived as a Twitter hashtag is a thought-provoking clue in support that it's important for us to take into account how public distress can influence the medical and diagnostic realms, and how much it – understandably – means to people in distress to have a voice. O'Sullivan is keen to re-emphasise, as I am too, that none of this is to suggest that people were not in very real distress, mental and physical, during the pandemic, and were then and continue to be deserving of support.
This is an incredibly difficult area to take on, in no small part because for too long too many people have been told to 'just get on with it', that they are oversensitive, lazy or weak for feeling the way they feel and having the symptoms they have. O'Sullivan manages to tackle the subject with courage, unfaltering compassion, nuance and graciousness. My hope would be that her insights and knowledge, gained over three decades of dedicated work, are considered with the same thoughtfulness that characterises them. A fear is that her well-researched argument could be jumped on by those who seek to make overdiagnosis and overmedicalisation an issue for the individual to tackle when, as is abundantly clear, this is a complex issue that involves systems at large.
To close, a point that O'Sullivan comes back to time and time again: diagnosis is more of a clinical art than a science. She acknowledges that this can be hard to accept, but is staunch in her opinion: that diagnosis should be a delicate and considered process, ideally carried out by expert diagnosticians with a lot of experience and a keen ability to bring together both scientific tests and the patient's symptoms, experience, and story. That even if diagnosis can be rightly made, treating it might still not be the right decision. That without taking into account the whole picture, we risk going against medicine's fundamental tenet to do no harm.
Watch our interview with Suzanne O'Sullivan here:
