Love can hurt, but not in the euphoric early phase of a romantic relationship. Then it's a potent painkiller that can stop pain signals from reaching the brain.
Researchers at Stanford University in California have found that intense, passionate feelings of love activate similar circuitry as analgesics such as codeine.
"At moderate pain levels, it is very effective. It is at least the equivalent as Tylenol 3, which has a little bit of codeine it in. I don't know if it would beat out OxyContin, but it could be very close,'' says Jarred Younger, an assistant professor of anesthesia at Stanford University in Palo Alto, Calif. Dr. Younger recruited volunteers who were in the heady first months of a romantic relationship for a brain-imaging study on love and pain.
Previous research has shown that looking at the photo of a romantic partner can reduce the amount of physical pain someone feels, but this is the first to show the brain regions involved. Love turns on reward circuitry in the brain, as do drugs such as cocaine or codeine, Dr. Younger said. Those drugs kick-start the body's analgesic systems, he said, and stop pain signals from leaving the spinal cord for the brain.
"The pain is blocked at spinal level. Love seems to work in those same channels."
The researchers say they hope their work leads to new approaches to treating pain, perhaps even to new drugs if they can learn more about how the love effect works and how to enhance it.
Dr. Younger also wants to see if enduring love is as effective a painkiller by doing a similar experiment with couples who have been happily married for 10 years. He also wonders if maternal love is an analgesic.
"It would be interesting to see if this is limited to passionate love."
This study was limited to students at Stanford in the first nine months of a relationship.
"We wanted subjects who were feeling euphoric, energetic, obsessively thinking about their beloved, craving their presence," Dr. Young said.
The eight women and seven men were giddy enough to agree to go into a functional magnetic resonance imager with a tiny computer-controlled hot plate called a "thermal stimulator" strapped to one of their palms. Earlier testing allowed the researchers to determine the temperature settings that would cause a moderate or high level of pain for each volunteer. The high setting was enough to make them grimace, but not enough to make them squirm.
For each volunteer, thinking about and looking at a photograph of their beloved was a balm. It had a dramatic impact on the levels of moderate pain they reported, reducing it by about 45 per cent compared to when they looked at a photo of a familiar acquaintance, Dr. Younger said. At the high-pain setting, the reduction was 11 per cent.
That was comparable to the reduction in pain they reported when researchers deliberately distracted them with word-association tasks, or by asking them to name sports that don't involve balls.
Distraction has also been shown to reduce pain, but this study showed that different brain circuitry is involved, said Arthur Aron, a psychologist at State University of New York who collaborated with Dr. Younger and Stanford's Sean Mackey.
"Comparing love to distraction was the most interesting part of this study. People talk about how when they are in love they can't think of anything else, so we thought it might be a distraction effect," he said. "But love is operating through a very primitive reward mechanism and distraction is operating through more frontal, cognitive system."
Dr. Aron has studied love for three decades. Several years ago, he met Dr. Mackey, an expert in pain, at a neuroscience conference.
"He was talking about the brain systems involved with love. I was talking about the brain systems involved with pain," Dr. Mackey said. "We realized there was this tremendous overlapping system. We started wondering, Is it possible that the two modulate each other?"
They teamed up with Dr. Younger for this study, which, like many brain-imaging studies, has a small sample size because detailed brain scans are so expensive. They published their findings on Wednesday in the Public Library of Science journal PLoS One.