The study also suggests dreaming may occur when patients are coming out of anaesthesia when the brain is still affected by the sedatives.
The researchers examined 300 health patients aged 18 to 50, during elective surgery.
About 22 percent of the patients reported dreaming upon emergence.
The study reads: “This is consistent with previous studies in which patients were interviewed immediately after emergence.
“We attribute the high incidence of dreaming at our two to four hour interview to reinforcement of memories of dreaming produced by the first interview, because dreams are usually hard to remember unless actively recalled.”