Men and women experience pain relief differently. A new study from University of California – San Diego explains why women have more chronic pain and seemingly less responsive to opioid treatments.
This arises because men and women rely on different biological systems for pain relief, which explains why the most powerful pain medications are often less effective in women.
This was based on research evaluating meditation for chronic lower back pain. This showed that men relieve pain by releasing endogenous opioids, the body’s natural painkillers. In contrast, women rely instead on other, non-opioid based pathways.
Synthetic opioid drugs, such as morphine and fentanyl, are a powerful class of painkilling drugs. It also stands that women generally respond poorly to opioid therapies, based on the use of synthetic opioid molecules to bind to the same receptors as naturally-occurring endogenous opioids.
This aspect of opioid drugs helps explain why they are so powerful as painkillers, but also why they carry a significant risk of dependence and addiction.
According to Fadel Zeidan, professor of anaesthesiology: “Dependence develops because people start taking more opioids when their original dosage stops working. Although speculative, our findings suggest that maybe one reason that females are more likely to become addicted to opioids is that they’re biologically less responsive to them and need to take more to experience any pain relief.”
The study combined data from two clinical trials involving a total of 98 participants, including both healthy individuals and those diagnosed with chronic lower back pain.
Study participants underwent a meditation training program, then practiced meditation while receiving either placebo or a high-dose of naloxone, a drug that stops both synthetic and endogenous opioids from working. At the same time, they experienced a very painful but harmless heat stimulus to the back of the leg.
The researchers then measured and compared how much pain relief was experienced from meditation when the opioid system was blocked versus when it was intact.
The study also found that when blocking the opioid system with naloxone inhibited meditation-based pain relief in men, that men rely on endogenous opioids to reduce pain. In contrast, naloxone increased meditation-based pain relief in women, suggesting that women rely on non-opioid mechanisms to reduce pain.
Overall, in both men and women, those with chronic pain experienced more pain relief from meditation than healthy participants.
The researchers recommend more sex-specific pain therapies, since many of the treatments applied do not work nearly as well for women as they do for men.
The research features in the journal PNAS Nexus, titled “Self-regulated analgesia in males but not females is mediated by endogenous opioids.”
