Pain is normal. About 75 million U.S. residents endure chronic or recurrent pain. Migraines plague 25 million of us. And one in six suffer arthritis.
The global pain industry pulls in more than $50 billion in drugs a year. Yet for chronic pain sufferers, over-the-counter pills are typically little help, whereas morphine and other narcotics can be addictive sedatives.
An overview study published in 2008 in the Journal of General Internal Medicine looked at multiple studies of pain and found "researchers don't yet know how to determine which [treatment] is best for individual patients." From studies of drugs to surgeries and alternative medicines, "We have found that there are huge gaps in our knowledge base," said Dr. Matthew J. Bair, assistant professor of medicine at the Indiana University School of Medicine.
Here's a look at six surprising facts about that achy sensation whose scientific understanding is painfully fuzzy.