Nearly one in three children admitted in pediatric intensive care units (PICU) will have delusional memories, new research reveals.

The study, believed to be the largest on children’s experiences in an intensive care unit, shows that delusions were more common in children who had to be sedated for more than two days and in youngsters who were admitted on an emergency basis.

“I have worked for 16 years in pediatric intensive care and have seen a considerable number of children in distress, but have found that there is very little in the literature about children's experiences,” said study author Gillian Colville, a consultant clinical psychologist and head of the pediatrics psychology service at St. George's Hospital in London, Reuters reports.

For the study, Dr. Colville and her colleagues evaluated 102 children between the ages of 7 and 17 and up within three months of discharge from the pediatric intensive care unit at Great Ormond Street Hospital for Children in London. The children were surveyed about their memories and given a screening test for post-traumatic stress symptoms (PTSD).

The study found that the hallucinations were usually around the time the children were being weaned off sedatives (opiates and benzodiazepines), medications used to help control pain and anxiety while in intensive medical care.

“In the majority of cases, these delusional memories consisted of one or more hallucinations which were often frightening and which the children could still recall vividly. [Children] reported seeing rats, cats, scorpions on the walls and, in some cases, crawling on the bed, and a couple of children were convinced that their parents had been replaced by imposters,” Dr. Colville said.

The study also found that sixty-three percent of the children had at least one factual memory of their hospital stay, such as seeing their parent at their bedside when they woke. Also, thirty-two percent of children reported having delusional memories and the chance of having a delusional memory increased nearly fivefold if they were sedated for more than two days.

One in four children scored enough on their tests to be considered as having post-traumatic stress disorder and the risk of PTSD was even higher in the case of children who reported having delusional memories.

“Some of the symptoms that define PTSD involve the person reexamining what happened in the form of intrusive memories, sometimes known as flashbacks. These memories are likely to be of the particularly distressing parts of what happened and are associated with strong emotions of fear and threat. On the whole, the children interviewed were much more distressed by their delusional memories than by the factual memories they experienced,” Dr. Colville explained.

Therefore, she does not suggest that the drugs be discontinued, but she does warrant further study, which could establish whether alternative types of sedation or the introduction of drug holidays might produce fewer traumatic delusional memories. Also, parents and doctors should provide psychological orientation cues for these children, such as day and night, to help reduce these symptoms.

“But above all, medical professionals and families should be made aware of the possibility that children may have these disturbing hallucinatory experiences, and greater efforts should be made to monitor their psychological adjustment after PICU,” Dr. Colville said.

She also added that the findings mimic studies in adults, who also report higher rates of hallucinations after an intensive care stay and are at higher risk of PTSD.

This research appears in the first issue for May of the American Journal of Respiratory and Critical Care Medicine, published by the American Thoracic Society.