Pauline first became ill when she was 15. What seemed to be a urinary infection became joint pain, then life-threatening appendicitis. After a routine operation Pauline lost all the strength in her legs. Shortly afterwards, convulsions started. But Pauline’s tests are normal: her symptoms seem to have no physical cause whatsoever.

This may be an extreme case, but Pauline is not alone. As many as a third of people visiting their GP have symptoms that are medically unexplained. In most, an emotional root is suspected which is often the last thing a patient wants to hear and a doctor to say.

We accept our hearts can flutter with excitement and our brows can sweat with nerves, but on this journey into the very real world of psychosomatic illness, Suzanne O'Sullivan finds the secrets we are all capable of keeping from ourselves.