Why More People Are Living With Symptoms They Cannot Easily Explain

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For some people, the most frustrating part of being unwell is not having a diagnosis they dislike. It is having symptoms that are real, persistent and disruptive, while medical tests fail to provide an obvious explanation.

Pain, dizziness, exhaustion, heart palpitations, digestive problems, headaches, breathlessness, sleep disturbances and difficulties concentrating can occur across many different conditions. Sometimes they eventually lead to a clear diagnosis. Sometimes they are associated with a recognized condition whose mechanisms are still being studied. And sometimes the symptoms remain difficult to explain even after medical evaluation.

That does not mean there is nothing wrong.

Modern medicine is exceptionally good at identifying many diseases, but a normal scan, blood test or examination does not necessarily explain everything a person experiences. Persistent physical symptoms can arise through complicated interactions involving biological processes, the nervous system, previous illness, pain processing, sleep, stress and other factors. In some cases, several mechanisms may operate at the same time.

The challenge is therefore not simply finding “the missing disease.” It is understanding why symptoms can be genuine and disabling even when conventional testing does not produce a straightforward answer.

Key Takeaways

• Unexplained symptoms are real physical experiences, not evidence that a person is pretending or simply imagining illness.
• A normal test can rule out some conditions without explaining every symptom a person experiences.
• Persistent physical symptoms can involve biological, neurological, psychological and social factors at the same time.
• Long COVID has highlighted how disabling symptoms can persist despite routine investigations being unrevealing.
• Medical terminology is changing because labels based entirely on what doctors cannot find can unintentionally invalidate patients.
• Persistent or changing symptoms still require appropriate medical assessment rather than automatic attribution to stress or anxiety.

The Problem With Calling Symptoms “Unexplained”

The phrase “medically unexplained symptoms” sounds definitive, but it often describes a limitation of current understanding rather than proof that no physical process exists.

The NHS describes medically unexplained symptoms as persistent physical symptoms for which clinicians cannot identify a medical condition that adequately explains them. Examples include pain, dizziness, tiredness, faintness, palpitations and digestive problems. The NHS also explicitly notes that these symptoms are real and can interfere with normal functioning.

That distinction matters.

A patient may hear “your tests are normal” as “nothing is wrong.” Clinically, those statements are not necessarily equivalent. A test is designed to detect particular abnormalities. A normal result can make some diagnoses less likely without providing a complete explanation for the person’s experience.

This is one reason contemporary medicine increasingly uses terms such as persistent physical symptoms in addition to, or instead of, older terminology such as medically unexplained symptoms.

Research has also highlighted the difficulty of defining these symptoms consistently. A systematic review published in BMJ Open found substantial variation among studies in how medically unexplained symptoms were defined and measured, making simple estimates of prevalence difficult.

The terminology is therefore part of the problem: what looks like a single category from the outside can contain many different clinical situations.

Why a Symptom Can Be Real Without a Simple Test Result

Medicine has traditionally relied heavily on identifying abnormalities in organs, tissues, blood chemistry or imaging.

That approach is essential. But many symptoms depend on how complex biological systems function rather than on one visible structural abnormality.

Pain is a useful example.

Two people can have similar findings on an imaging scan but experience very different levels of pain. Conversely, a person can experience substantial pain without an obvious structural abnormality that accounts for its intensity.

NICE distinguishes between chronic secondary pain, where an underlying condition adequately accounts for the pain, and chronic primary pain, where there is no clear underlying condition or where the pain or its impact is out of proportion to an observable injury or disease.

NICE also emphasizes that chronic pain can be influenced by biological factors alongside social circumstances, emotional factors, expectations, beliefs, mental health, sleep and other aspects of a person’s life.

That does not reduce pain to psychology.

It reflects a more complicated model of how the nervous system and the body interact.

The same principle can apply to symptoms such as fatigue, dizziness, gastrointestinal discomfort or cognitive difficulties. The absence of a single abnormal test does not automatically identify the cause, because there may not be one simple cause to identify.

The Post-COVID Experience Changed the Conversation

Long COVID has provided one of the clearest recent examples of why difficult-to-explain symptoms deserve careful attention.

According to the U.S. Centers for Disease Control and Prevention, Long COVID can involve symptoms that persist, disappear and return, or change over time. Reported symptoms include fatigue, post-exertional malaise, difficulty concentrating, dizziness, palpitations, headaches, shortness of breath, digestive problems and sleep disturbances.

The CDC states that there is currently no approved laboratory test that can determine whether a person’s symptoms are caused by Long COVID. Routine investigations can also be normal in someone who has the condition.

This creates an important distinction between absence of evidence from a particular test and evidence that the symptoms are not genuine.

Long COVID has also demonstrated why diagnosis can become difficult when a condition affects multiple systems and does not behave like a conventional single-organ disease. The CDC describes Long COVID as a heterogeneous condition that can involve one or more organ systems, with possible mechanisms still being investigated.

The significance extends beyond COVID-19.

It has made the broader medical challenge easier to see: some chronic conditions cannot yet be reduced to one biomarker, one scan or one laboratory result.

Why More Symptoms Do Not Necessarily Mean More Disease

The headline question why more people are living with symptoms they cannot easily explain needs an important qualification.

There is insufficient evidence to conclude that every form of unexplained physical symptom is increasing in prevalence.

What has changed may be a combination of several things: recognition, terminology, survival after serious illness, awareness of post-infectious conditions, improved attention to chronic symptoms, and the ability of patients to describe complex symptom patterns that do not fit neatly into established disease categories.

Long COVID is an obvious example of a condition that has brought large numbers of persistent symptoms into clinical and public discussion.

At the same time, persistent physical symptoms are not new. Research predating the pandemic found them frequently in primary care and specialist settings. A 2022 systematic review in BMJ Open described medically unexplained symptoms as common and found that persistent symptoms could be associated with disability, poorer quality of life and greater healthcare use.

The better interpretation, therefore, is not that medicine has suddenly discovered a new epidemic of unexplained illness.

It is that a longstanding clinical problem has become more visible while medicine is simultaneously confronting new forms of complex chronic illness.

The Risk of Dismissing Symptoms as “Just Stress”

Stress, anxiety and depression can influence physical symptoms. That is medically important, but it becomes harmful when the relationship is oversimplified.

The NHS notes that psychological problems can accompany persistent physical symptoms and that each can sometimes worsen the other. NICE similarly recommends considering psychological and social factors as part of a comprehensive assessment of chronic pain.

The correct conclusion is not that unexplained symptoms are psychological.

It is that physical symptoms and psychological states can interact.

Pain can produce anxiety. Poor sleep can increase fatigue. Persistent symptoms can make ordinary activities more difficult. Worry about unexplained symptoms can increase distress, while distress can affect how symptoms are experienced.

These relationships can operate simultaneously with biological processes.

For patients, the distinction matters because being offered psychological support should not automatically mean that clinicians believe symptoms are imaginary. Evidence-based psychological therapies can be part of symptom management for certain chronic conditions without implying that the underlying experience is fabricated.

A Diagnosis Can Also Change Over Time

Another important point is that medical diagnosis is not always a one-time verdict.

NICE specifically advises clinicians to recognize that an initial diagnosis of chronic primary pain may change over time and to reassess when the clinical presentation changes.

That principle has broader significance.

A symptom that cannot currently be explained should not simply be placed into a permanent “unexplained” category and forgotten. New symptoms, changing patterns or new examination findings can alter the clinical picture.

This is why appropriate follow-up matters.

Patients should also be able to communicate what has changed, what triggers symptoms, how symptoms affect daily activities, and whether new problems have appeared. Those details can be clinically useful even when an earlier investigation was normal.

What Patients Can Do When the Explanation Is Still Unclear

Someone experiencing persistent or unexplained symptoms should not try to diagnose themselves from an online article.

A more useful approach is to make the clinical history as clear as possible.

Before an appointment, it can help to record:

• when the symptoms began;
• whether they are continuous or come and go;
• what makes them better or worse;
• how they affect sleep, work, exercise and daily activities;
• significant illnesses or infections that preceded them;
• medicines and supplements being taken;
• new or changing symptoms;
• questions about previous test results and what those tests actually ruled out.

The NHS recommends telling a doctor what symptoms feel like, when they began, what affects them, how they limit activities and what concerns the patient has about their cause.

Importantly, persistent symptoms should not automatically be self-labelled as “medically unexplained.” A clinician may need to reassess the situation, particularly when symptoms are new, worsening or substantially different from before.

What Medicine Is Learning From the Diagnostic Gap

The larger lesson is about the limits of a purely test-centered view of illness.

A laboratory result is valuable because it measures something specific. Imaging is valuable because it can reveal particular structural or functional abnormalities. But neither necessarily captures the totality of a person’s health experience.

The growing focus on persistent physical symptoms reflects an attempt to bridge that gap.

It also explains why modern clinical guidance increasingly emphasizes person-centred assessment, communication and shared decision-making. NICE recommends that people with chronic pain be involved in decisions about their care and that clinicians communicate normal or negative test results sensitively so they do not inadvertently invalidate the patient’s experience.

This is more than a matter of bedside manner.

When patients feel dismissed, they may continue searching for explanations through repeated appointments, tests or unverified treatments. A more constructive clinical relationship can instead acknowledge uncertainty while still establishing a plan for evaluation, symptom management and follow-up.

The Unanswered Question Is Not Always “What Disease Is This?”

For some patients, the most useful medical question may eventually become broader than identifying a single disease.

It may be:

What mechanisms are contributing to these symptoms, what can safely be ruled out, what can be treated, and how can the person’s ability to live normally be improved?

That approach does not abandon diagnosis. It keeps diagnostic reassessment available while recognizing that symptom relief and functional recovery do not always require a perfect explanation first.

For conditions such as chronic primary pain, NICE already frames management around improving quality of life and function alongside addressing the symptoms themselves.

The same principle is increasingly relevant to a wider group of patients whose symptoms cross conventional diagnostic boundaries.

Conclusion

Living with unexplained symptoms is not the same as living with imaginary symptoms.

The evidence shows that persistent physical symptoms are common enough to represent a significant challenge for healthcare, yet the category itself contains very different conditions and mechanisms. Some symptoms eventually receive a specific diagnosis. Others are associated with recognized but incompletely understood conditions. Still others remain difficult to explain even after appropriate investigation.

The rise of Long COVID has made this diagnostic gap harder to overlook, but the problem existed long before the pandemic.

The most responsible response is neither to assume that every unexplained symptom represents a hidden disease nor to dismiss symptoms because standard tests are normal. The better approach is continued clinical assessment, honest communication about uncertainty, attention to the whole person, and a willingness to revise an explanation when the evidence changes.

For patients, that distinction is crucial: “we do not yet know exactly why this is happening” is very different from “nothing is happening.”