“Symptoms can include general weakness and paralysis, tremors and unsteady gaits, and sensory problems such as hearing loss, blindness, and numbness”“An unusual form somatic symptom disorder is pseudocyesis, or phantom pregnancy”John Watson's phantom limp in BBC's SherlockAs our understanding of diseases continues to expand, George Merrin explains what psychosomatic illnesses and injuries are and why there is so much mystery around them.[br]Have you ever had a phantom pain come and go and been unable to explain its origin? Have you ever gone to a doctor only to discover that they too are unable to determine the source of the pain? If you answer yes to either of these then you may have a form of psychosomatic illness.Psychosomatic refers to anything relating to the interactions between the body and the mind. To put this in context, a psychosomatic illness is an illness which can be made worse by mental factors such as depression and anxiety. Yet how these factors alter the physical body is still undetermined. For anxiety, symptoms such as an increase in heart rate, palpitations, chest pain, and sweating are not psychosomatic as they are caused by the excretion of adrenaline.Anxiety however affects certain diseases, such as eczema as it can increase the spread of the rash, heart disease as it can increase blood pressure, and it can cause psoriasis (a form of skin disease) to flare-up. Thesediseases can therefore be called psychosomatic disorders.Somatoform Symptom Disorder (SSD) is a mental illness which causes bodily symptoms such as pain. The difference between psychosomatic and somatoform disorders is that in the latter no physical damage is done. There are many types of SSD. One such disorder is illness anxiety disorder. This was formerly known as hypochondriasis and occurs in people who continuously believe they have a serious medical condition. This can beseen where a person has a minor headache and believes this to be a symptom of a brain tumour.Another form of SSD are Conversion Disorders, which are also commonly called Functional Neurological Symptom Disorders. They are disorders that affect the brain, i.e. they have neurological symptoms, yet there are no known medical causes. Symptoms of this can include general weakness and paralysis, tremors and unsteady gaits, and sensory problems such as hearing loss, blindness, and numbness.An unusual form somatic symptom disorder is pseudocyesis, or phantom pregnancy. This is when a woman believes she is pregnant and even has physical symptoms such as abdomen enlargement, foetal movements,etc. despite the fact she isn’t pregnant.Injuries can also be psychosomatic, common to people with Post Traumatic Stress Disorder (PTSD). This was portrayed in popular culture in BBC’s Sherlock, as Dr. John Watson starts out the series with a limp, however in later episodes all evidence of his once crippling affliction is gone. To put it in simple terms, his leg was never injured, it was a physical manifestation of his internal feelings of worthlessness and incompetence. So when he found his purpose it vanished as if it never existed. PTSD has many difference physical and mental manifestations, however chronic pain is one which can be either somatoformic in origin, or evolve into one.There is still a lot to learn about psychosomatic illnesses and injuries. Before MRI was invented in 1977, multiple sclerosis was believed to be a form of hysterical paralysis. With advances in imaging techniques and modern medicine, soon we may be able to explain some if not all the mystery that surrounds these puzzling conditions.