A study done by Clemson University in South Carolina showed that opioid hormones may be related to changes in both blood pressure (BP) and sensitivity to pain in patients with early-stage hypertension. The results of the study were published in the January/February 2006 issue of the medical journal Psychosomatic Medicine.

According to researchers, patients with hypertension have reduced pain sensitivity, which also appears in young people at risk for hypertension. They suggest that altered sensitivity to pain may be a part of the early development of hypertension. The exact relationship between the 2 conditions is not clear, however.

Researchers studied the effects of natural opioids, such as endorphins and enkephalins, on pain perception and BP in 125 young adults with mildly elevated BP. On different occasions, participants were given the opioid blocker naltrexone or placebo 60 minutes before their pain threshold was tested by immersing their hands in ice water for 2 minutes or as long as they could bear. The results showed that BP rises as sensitivity to pain drops, whether or not natural opioids are blocked. This finding indicates "a greater degree of opioid analgesic tone in young persons at risk for hypertension," the researchers said.