He said: 'We have had patients who have reported sending text messages to their friends and family while asleep.
'It is one of those things that happens, but it is very rare, and certainly not a common trend.'
Unsurprisingly, there are no studies into sleep texting - but a similar phenomenon, sleep emailing, was studied in 2008.
Researchers at the University of Toledo reported the case of a woman, 44, who would compose emails while sound asleep. She had no recollection of sending the emails when awake.