About one-third of children in pediatric intensive care units experience frightening delusions that stay with them for a longer time, a new study has found. Powerful hallucinations where children reported seeing various animals like cats and spiders were most common in children who had to be sedated for more than two days, and in youngsters who were admitted on an emergency basis.

According to a study in the first May issue of the American Journal of Respiratory and Critical Care Medicine, these delusional memories put the children at far higher risk of post traumatic stress disorder.

The children were five times more likely to report delusions or hallucinations when they were weaned off strong sedatives such as opiates or benzodiazepines. Such medications are used to help control pain and anxiety in children, and in adults, who need intensive medical care.

Study author Gillian Colville, a consultant clinical psychologist and head of the pediatrics psychology service at St. George's Hospital in London said in a press release that "a couple of children were convinced that their parents had been replaced by imposters."

The reason why the children experience such delusions was that the sedatives, and benzodiazepines in interfere with the ability to form new memories and normal sleep making it more difficult to process information and memory.

Researchers now recommended that parents and caregivers be supportive and honest to the children about their treatment and assure them that other children too have experienced the same types of hallucinations.