Ever wonder why you need to take twice as many pain pills as your friend for the same type of injury? Pain is influenced by a lot of factors, but according to new research by scientists at the Children's Hospital of Philadelphia, you can blame part of it on your genes.

Publishing in the journal Pain, the interdisciplinary group recently identified variants in a gene called TAOK3 that were linked to a higher demand for opiate painkillers among children following surgery to remove their tonsils and adenoids.

Whereas some kids needed only one milligram, CHOP pediatric anesthesiologist and lead author Scott Cook-Sather said others required 10 milligrams to be comfortable. The variants in TAOK3 accounted for 8 percent of that variability, he said -- similar to the amount related to age, body mass index, and physical status combined. If children inherited both copies of a variant from their parents, they needed 22 percent more morphine than their peers

"It's overall maybe a small effect," said Cook-Sather, "but very much a sizable effect when you take into account the other clinical factors that go into predicting morphine dose."

The effect was strongest in children of European ancestry. The team is planning on recruiting far more children to investigate how large a role the variants play in African-Americans.

The finding points to one way doctors may someday be able to manage pain without prescribing more painkillers.

"There may be pharmaceuticals which can alter the TAOK3 gene," said Cook-Sather, "and these pharmaceuticals could be used to perhaps offset this resistance that some children have to morphine."

Along with that avenue of research, the group is working on ways to use multiple genes to predict which young patients would need more medicine.