Smearing fake faeces on rubber hands may help OCD sufferers overcome fears of touching dirty surfaces, scientists say.
An obsession with washing and cleaning to get rid of germs affects almost half of patients with the mental health condition.
Many doctors gradually attempt to coax patients out of their fear by getting them to touch dirty surfaces, such as toilet seats, and not wash their hands.
However, this can be extremely stressful, rendering exposure therapy – as it is called – useless because patients stop taking part.
Cambridge University neurologists now claim the bizarre ‘rubber hand illusion’ could help thousands of patients to receive treatment, after carrying out a study of the technique on 29 OCD patients.
Hope has been raised for OCD sufferers after a study found smearing faeces on a fake hand can help them overcome fears of contamination. A fake hand is laid in front of the patient, and their own hand is hidden behind a partition (pictured)
In the therapy, a rubber hand is laid in front of the patient. Their own hand is hidden behind a partition.
Participants watch fake faeces being smeared on the rubber hand while the medic dabbed a damp paper towel on the volunteer’s real right hand to mimic the feeling of faeces touching their own skin.
Lead author Baland Jalal said: ‘OCD can be an extremely debilitating condition for many people, but the treatments are not always straightforward.
‘Exposure therapy can be very stressful and so is not always effective or even feasible for many patients.’
OCD affects as many as one in 50 people worldwide, figures show. The condition can manifest itself in various ways.
One type is characterised by excessive washing or cleaning because the sufferers are terrified they might become contaminated by germs.
Mr Jalal said the results of the study suggest fake hand contamination may enable more patients to get treatment.
‘The rubber hand illusion often makes people laugh at first, helping put them at ease,’ he said.
‘It’s also straightforward and cheap compared to virtual reality, and so can easily reach patients in distress no matter where they are.’
The study, which also involved researchers at Harvard University, involved 29 OCD patients.
The aim of the study was to assess whether patients needed the fake hand and their own hand stroked in sync for the exposure therapy to work.
It did not compare how successful exposure therapy was with or without a fake hand.
Sixteen patients had their hidden and dummy hands stroked with the paintbrush at the same time.
While the remaining 13 patients – the control group – had their hands stroked out of sync.
After five minutes of stroking, the patient was asked to rate how much the rubber hand felt like their own.
The participant was then asked to rate their disgust, anxiety and handwashing urge levels after fake faeces was smeared on the rubber hand, while a damp towel was dabbed on their own.
The researchers found patients in the experimental and control group equally felt the fake hand as their own.
Therefore, patients in both groups initially reported similar levels of contamination.
However, the patients in the experimental group felt more disgusted the longer the study went on. Disgust was measured by facial expressions.
After five minutes, 65 per cent of patients in the experimental group were disgusted, compared with 35 per cent in the control group.
Next, the experts stopped the stroking and placed the fake faeces on the patient’s right hand. The differences between the groups became even more pronounced.
Those in the control group had average disgust, anxiety and washing urge levels, ranking at nearly seven.
But the patients in the experimental group had slightly higher levels. The results were published in the journal Frontiers in Human Neuroscience.
Mr Jalal said: ‘Although this was the point our experiment ended, research has shown that continued exposure leads to a decline in contamination feelings – which is the basis of traditional exposure therapy.
‘If you can provide an indirect treatment that is reasonably realistic, where you contaminate a rubber hand instead of a real hand, this might provide a bridge that will allow more people to tolerate exposure therapy or even to replace exposure therapy altogether.’