Munchausen's syndrome is a rare psychological and behavioural condition in which somebody fabricates or induces symptoms of illness in themselves.

Munchausen's syndrome is named after a German aristocrat, Baron Munchausen, who became famous for telling wild, unbelievable tales about his exploits and past.

People with Munchausen's syndrome typically display a set pattern of behaviour. This pattern includes:

• lying about their symptoms and typically also lying about other aspects of their life, such as their past or level of education,
• manipulating test results to suggest the presence of symptoms, such as adding blood to urine samples,
• actually inflicting symptoms on themselves, such as poisoning themselves with an overdose of medication, and
• travelling from hospital to hospital in different parts of the country, and seeing many different doctors.

Munchausen's syndrome differs from two, more common, types of feigned illness, hypochondria and malingering. People who have hypochondria actually believe they are ill, but do not manipulate test results. People who malinger pretend to be ill to gain some sort of benefit, such as avoiding military duty or trying to obtain compensation.

People with Munchausen's syndrome know they're making their symptoms up and can be highly manipulative, but their behaviour brings them no obvious benefit. Instead, they often undergo painful and sometimes life-threatening surgery, even though they know it is unnecessary.

How common is Munchausen's syndrome

It is hard to estimate how many people are affected by Munchausen's syndrome. They tend to be highly secretive and often use a number of false identities. Once their deception is uncovered they discharge themselves from hospital and move to another area.

The condition is thought to be most common in white men aged between 30 and 50. It is unclear why this is the case.

The causes of Munchausen's syndrome are largely unknown. Most people who have been diagnosed with the condition refuse to accept any sort of psychiatric treatment so little is known about their motives or thought processes.

There is a variant of Munchausen's syndrome, called Munchausen's syndrome by proxy, in which an individual fabricates or induces illness in a person under their care, typically a child.