Last week the Kiama MP was twice escorted back to his Potts Point apartment by police after being found wandering around the building.

Police were called by another resident, concerned that a naked Mr Ward was banging on their apartment door.

Mr Ward later issued a statement that said he had become disorientated after a medical procedure done under general anaesthetic.

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Dr Robert Kaplan, a forensic psychiatrist working in the area of sleep medicine, said sleepwalking can occur as a result of an operation.

"That's quite feasible," Dr Kaplan said.

"Anything that you can call a physiological stress can trigger it off. You would also wonder, is there any family history of this? Did he himself sleepwalk as a child, because it actually does run in families."

While sleepwalking tends to be treated as amusing by the general public, Dr Kaplan said it can actually be deadly.

"It's the commonest cause of death while you're sleeping," he said.

"People walk out into streets and get knocked over, they fall down stairs, they walk through closed windows."

The less severe repercussions are "serious embarrassment and humiliation" - as in the case of Mr Ward.

Dr Kaplan told of a university lecturer whose career was threatened due to her sleepwalking while living in university accommodation.

Unable to lock all the doors to keep herself safe, she faced complaints from students who would find her in their rooms in the middle of the night.

Dr Kaplan said a sleepwalker can often give the appearance that they're conscious - a condition known as "purposeful automatism".

"The sleepwalker does not know what they are doing," Dr Kaplan said.

"They're in what is the deepest level of sleep and usually you have muscular paralysis, so you just lie in bed with whatever's going on in your head.

"But now the muscular paralysis breaks down and it takes the form of sleepwalking. It's also associated with sleep talking and things like that."

Mr Ward was contacted for comment.