Women and men process pain differently, using different biological systems for pain relief, according to a UC San Diego study that assessed meditation for relief of chronic lower back pain.

The UC San Diego study’s findings, published in PNAS Nexus, may help explain why women experience greater chronic pain but a lower response to opioid treatments.[1][2]

Women and men process pain differently, using different biological systems for pain relief, according to a UC San Diego study that assessed meditation for relief of chronic lower back pain. The study’s findings, published in PNAS Nexus, may help explain why women experience greater chronic pain but a lower response to opioid treatments.[1][2]

 “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,” said corresponding author Fadel Zeidan, PhD, in a press release.[2]

Chronic pain prevalence

According to the CDC, around 20.9% of US adults (51.6 million) in 2021 experienced chronic pain—defined as pain lasting 3 months or longer—up from around 50 million in 2016.[3] Of the individuals with chronic pain, 6.9% (17.1 million) experienced high-impact chronic pain—chronic pain that results in substantial restriction to daily activities.

A higher prevalence of chronic pain exists among non-Hispanic American Indian or Alaska Native adults, bisexual adults, and individuals who were divorced or separated.

“Clinicians, practices, health systems, and payers,” the CDC urges, “should vigilantly attend to health inequities and ensure access to appropriate, affordable, diversified, coordinated, and effective pain management care for all persons.” 

Clinical implications

Chronic pain often continues “after the typical recovery period for an injury or illness,” Taher Saifullah, MD, founder of the Spine and Pain Institute in Los Angeles, who was not involved in the study, has said.[4] However, it “can occur without a specific cause and may be constant or come in waves, varying in intensity.”

“Chronic pain can significantly impair quality of life, leading to issues like disrupted sleep, depression and reduced physical functionality.”

-Dr. Saifulla 

Edgar Ross, MD, director of the Pain Management Center of Brigham and Women’s Hospital in Boston, has suggested that managing chronic pain requires a team approach, with the patient participating in the active treatment plan. This contrasts with the situation in acute pain, which often requires an intervention by a healthcare professional, with the patient being the passive recipient.[5]

Dr. Ross noted that pain management must address the three components of pain, of which the first is nociception. You can address the pain sensation with medication, implants, or nerve blocks, he explained. The psychological component, the second, includes anxiety and depression from dealing with chronic pain. Additionally, a person with poorly treated depression or anxiety will perceive more pain.

Self-regulated pain relief

The PNAS Nexus authors noted that females experience more chronic pain and receive more opioid prescriptions than males, despite evidence that opioids are less effective in females, leading to greater opioid misuse and addiction. They undertook the study to discover if the endogenous opioid system, which is fundamental to analgesia and psychological resilience, is engaged differentially in men and women during self-regulated analgesia via meditation.[1][2]

For the study, the investigators combined data from two trials involving 98 adults (women 51, mean age 37.6; men 47, mean age 39.4). Of the participants, 59 had chronic lower back pain and 39 were deemed healthy and pain-free.

By randomisation, participants completed either a validated or a sham four-session mindfulness meditation training program. Then, all participants engaged in meditation while receiving a placebo (saline injection) or a high dose of naloxone, an opioid antagonist. At the same time, the participants were administered a heat stimulus at 49°C to the back of the calf, evoking a pain response. The participants recorded their pain ratings using a visual analogue scale (scored from 0-10, for no pain to worst pain imaginable).

In men, naloxone inhibited meditation-based pain relief, suggesting that men relieve pain by releasing endogenous opioids. In women, naloxone increased meditation-based pain relief, suggesting that women rely on non-opioid-based pathways to reduce pain. Both men and women with chronic lower back pain experienced more pain relief from meditation than did the healthy participants.

"There are clear disparities in how pain is managed between men and women, but we haven’t seen a clear biological difference in the use of their endogenous systems before now,” said Dr Zeidan. “This study provides the first clear evidence that sex-based differences in pain processing are real and need to be taken more seriously when developing and prescribing pain treatment.”[2]

Disclaimer: This story is contributed by Katie Robinson and is a part of our Global Content Initiative, where we feature selected stories from our Global network which we believe would be most useful and informative to our doctor members.