Medically Unexplained Symptoms

Introduction

Medically unexplained symptoms (MUS) are physical symptoms in the body which are not secondary to an underlying physical condition but can be understood by other factors. Symptoms can involve any bodily system.¹  

ICD 11 (International Classification of Diseases) and DSM 5 (Diagnostic and Statistical Manual of Mental Disorders) use the term “functional” for diagnostic purposes.² They may also be described as somatic symptoms.³

25-50% of symptoms presented in primary health care are medically unexplained and 2.5% of patients in general practice meet the criteria for persistent or severe MUS.¹

Aetiology 

Two-way communication occurs between the brain and body via the nervous system and hormones. This is sometimes called the mind-body link.

Thoughts, feelings, and stresses make physical changes in the body. This may be through the fight or flight response, where the brain recognises danger and releases adrenaline to prepare it for action. Physical changes can also occur through the disruption of messages between the brain and body via the nervous system and hormones. In addition, physical disease can also affect thoughts and feelings.³

Symptoms also can be understood due to neural circuit abnormalities, which alter the constructs in the brain.⁴

Risk factors 

Stress is a significant factor in the development of MUS. This may come from any aspect of the patient’s life, including home, school, work, family, friends, and relationships. There is also often an association with past or recent abuse.⁵

MUS are more likely if there is a history of mental health conditions such as depression or anxiety, particularly health anxiety. Mental health conditions can also cause physical symptoms.³

Clinical features

The most common symptoms reported include:³

• Muscular or joint pain, particularly in the back
• Headaches
• Fatigue
• Dizziness
• Chest pain
• Palpitations
• Gastrointestinal symptoms: pain, bloating, change in bowels
• Neurological symptoms: seizures, weakness, paralysis, numbness

A relevant clinical examination is required to exclude organic pathology. Symptoms are unlikely to improve following the exclusion of physical disease.³

Investigations 

Relevant investigations are essential to exclude organic aetiology of presenting symptoms. These will depend on the presenting clinical features. 

Diagnosis 

MUS and functional disorders are not diagnoses of exclusion but positive diagnoses.

They are diagnosed by conducting biopsychosocial assessments by psychologists and psychiatrists in conjunction with physical health doctors and other allied health care professionals (e.g. physiotherapists and occupational therapists) to understand the pathophysiology of the symptoms.

Diagnoses for specific patterns of MUS include:³

• Irritable bowel syndrome (IBS)
• Fibromyalgia
• Non-epileptic attack disorder (NEAD)

Diagnoses due to the causes of these symptoms include:³

• Somatoform/somatisation disorder: symptom(s) thought not to be physical in origin
• Dissociative/conversion disorder: neurological symptoms
• Hypochondriasis: concerns about specific illnesses rather than symptoms
• Body dysmorphic disorder: concerns about a feature of the body

Persistent delusional disorder should also be considered if the concern is a fixed unshakable belief 

Management 

The whole team must be aware of the diagnosis and management plan to ensure consistent management. Involvement of a multidisciplinary team, including psychology & psychiatry, is often required.⁵

Patient education around diagnosis and management of stress is important. Reassurance alone is often not effective. It is helpful to encourage patients away from further research and investigation for their symptoms.

Talking therapies such as cognitive behavioural therapy (CBT), psychotherapy, and mindfulness may be used. Physical exercise has been shown to be beneficial.⁵

Antidepressants may have some effect, partially due to the treatment of co-morbid depression.³

Symptoms will decrease in 50-75% of patients over 6-15 months. If symptoms change, clinicians should reconsider the possibility of organic pathology.⁵

Complications 

There is currently a lack of training in medical school around MUS and limited guidelines for general practice, which can lead to suboptimal management.⁵

Complications may result from repeated and invasive investigations attempting to determine an organic cause of the symptoms.

Additionally, some doctors may give inappropriate treatment for organic disease to patients presenting with MUS. This includes risks to physical health and the use of healthcare time and resources. If not appropriately managed, MUS can lead to chronic disability.⁵

Key points 

• Medically unexplained symptoms/functional Symptoms are those where no physical health cause can be found
• Any symptom may not be explained by a physical health diagnosis but could be explained by a psychiatric or psychological cause due to the mind-body link
• They are often the result of stressors
• It is important to find a balance between adequately investigating a patient’s symptoms and avoiding excessive investigations that may cause the patient further distress
• Management involves consistency, education and stress management
• If not appropriately managed, MUS can lead to increased risk to the patient’s physical and mental health and use of significant amounts of healthcare time and resources

Reviewer

Dr Laavanya Damodaran

Consultant Paediatric Liaison Neuropsychiatrist

Birmingham Children’s Hospital

Editor

Dr Chris Jefferies

References

1. T Hartman, H Woutersen-Koch, H Van der Horst. British Journal of General Practice. Medically unexplained symptoms: evidence, guidelines, and beyond. 2013; 63(617) 625-626. 
2. International Classification of Diseases- 11 and Diagnostic and Statistical Manual of Mental Disorders 5
3. J Bolton, D Attard. Royal College of Psychiatry. Medically unexplained symptoms. November 2015. Available from: [LINK]
4. Drane DL, et al. (2000) A framework for understanding the pathophysiology of functional neurological disorder. CNS Spectrums
5. C Tidy, H Willacy. Medically Unexplained Symptoms – Assessment and Management. 21 Apr 2023. Available from: [LINK]