19 August 1999
Infant Pain May Have Long-Term Effects
by Kate Melville
Newborn infants who are exposed to a series of painful and stressful treatments display a variety of long-term effects as older children, including an altered response to pain and an exaggerated physiological response to stress, new research shows.
Researchers at Washington University School of Medicine, British Columbia Children's Hospital, and Arkansas Children's Hospital examined the growing body of evidence of long-term effects of early pain and stress on human infants.
"Pain and stress have been shown to induce significant physiological and behavioral reactions in newborn infants, even those born prematurely," said Fran Lang Porter, PhD, lead author of the research. "There is now evidence that these early events not only induce acute changes, but that permanent structural and functional changes may also result."
Newborn infants, including those born prematurely, have functional nervous systems that are capable of perceiving pain, the researchers say. While many physicians have become aware of the need for anesthesia during circumcisions, for example, little is routinely done for infants who may face repeated needle sticks and other stressful conditions while in a neonatal intensive care unit. The research is reported in the current issue of Developmental and Behavioral Pediatrics.
"Caregivers daily face discrepancies between what they believe should be done to alleviate the pain of their [infant] patients and what they actually do to reach that goal," said Porter.
"Much of the early evidence for the long-term effects of pain and stress on newborns has come from animal studies," said Porter. "For example, rats given daily injections of saline as infants showed an increased stress response in adulthood after receiving an electric shock or surgery, and this response was associated with changes in stress hormone receptors in certain regions of the brain."
In humans, premature infants who were exposed to - multiple noxious stimuli - in the neonatal intensive care unit were less sensitive and responsive to everyday pain at 18 months of age. In another study, full-term circumcised boys reacted more strongly than uncircumcised boys to the pain of a routine vaccination at four to six months. "While it remains unclear whether young infants can remember painful experiences as actual events, there is evidence that memory for pain may be recorded at a biological level," said Porter. "At six months of age, however, most infants appear capable of remembering-displaying fear in anticipation of a previously experienced painful procedure."