Scientists have suggested that a disorder of the immune system could create symptoms which are mistaken for psychotic conditions such as schizophrenia or bipolar.

A study by medical professionals at Oxford University indicates that as many as 1 in 11 cases may be a result of a person’s antibodies attacking the brain.

The research, which follows a UK-wide trial involving more than 200 people, is controversial but if the conclusions are correct, it may pave the way for new ways of treating patients.

Sarah Galloway, from Gateshead, was in the final year of her degree when she started to suffer from vivid hallucinations.

“I deteriorated in a matter of days,” the 25-year-old told the BBC. “I hallucinated that my body has morphed spiders’ legs or rabbit ears, I’ve seen them there, I’ve felt them there.

“I get strange ideas in my head that someone is trying to kill me or I have to kill someone, and then a lot of it has resulted in self-harm.”

Originally diagnosed with bipolar disorder, a routine blood test later revealed that in fact her immune system was malfunctioning and she was put on a new course of treatment.

Professor Belinda Lennox, a clinical psychiatrist at the university, said: “The implications of this [research] are that there are patients in mental health services now who will have these antibodies and could potentially be treated in a very different way.

“I think this is a really exciting advance for psychiatry as a whole, and every psychiatrist and patient with psychosis needs to be aware of this and to look for it and treat it assertively when we find it.”