Why Women's Pain Lasts Longer: Immune Cells and Testosterone Offer Biological Clues

Women are disproportionately affected by chronic pain conditions - fibromyalgia, migraine, temporomandibular disorders, and chronic widespread pain all occur more frequently in women, and when women and men experience the same acute injury, women tend to take longer to recover. The standard clinical response has often been to attribute this gap to differences in reporting or pain tolerance. A study published in Science Immunology from Michigan State University proposes a more specific biological explanation.

The research team, led by associate professor Geoffroy Laumet, identified a subset of monocytes - immune cells previously regarded primarily as precursor cells rather than active participants in neural signaling - that produce interleukin-10, or IL-10. This cytokine acts directly on pain-sensing neurons, signaling them to quiet down. In males, these IL-10-producing monocytes are substantially more active than in females, and the reason appears to be testosterone. When the team blocked male sex hormones, the cellular activity pattern reversed.

From Mice to Human Patients

The finding replicated across at least five independent experiments in mouse models. When Laumet's team reached out to Sarah Linnsteadt at the University of North Carolina at Chapel Hill - who was independently studying psychological outcomes in car accident patients - her human data told the same story. Men recovering from car accidents showed more active IL-10-producing monocytes and resolved their pain faster than women in the study cohort.

The convergence between controlled mouse experiments and human clinical data is scientifically meaningful. Many pain biology findings have failed to translate from animal models to humans, so the parallel observation in two independent datasets strengthens the case that the monocyte-IL-10 pathway is clinically relevant.

Jaewon Sim, a former graduate student in Laumet's lab who contributed centrally to the discovery, described the moment the data became clear. "That was the turning point for me. I feel extremely fortunate that we trusted those early, uncertain findings and chose to pursue them further."

Reframing Chronic Pain as an Active Process

The standard model of pain emphasizes initiation - what activates pain-sensing neurons, and how to block those signals pharmacologically. Opioids and most conventional analgesics work by suppressing pain transmission. Laumet's work takes a different angle, asking why pain sometimes fails to resolve even when the original injury has healed. Pain resolution, the new data suggest, is not passive but actively driven by the immune system.

"This study shows that pain resolution is not a passive process," Laumet said. "It is an active, immune-driven one."

This reframing opens a different therapeutic direction. Rather than blocking pain signals after they have started, treatments could aim to boost IL-10 production by monocytes, accelerating the resolution pathway. Laumet described this as a potential route to non-opioid therapies. These treatments would not simply suppress pain signals - they would recruit the body's own immune machinery to end them.

A Distant Horizon

Any practical treatment is far off. Laumet estimates a new therapy based on this pathway is probably decades away. The monocyte-IL-10 mechanism is now identified and validated in mouse and human observational data, but the steps between that and a clinically approved drug are many: identifying specific molecular targets within the pathway that are druggable, developing compounds, testing them for safety and efficacy, and navigating regulatory approval. Early-stage mechanistic discoveries regularly fail to produce treatments even when the biology seems sound.

Still, the study's contributions are real and immediate. It provides a biological explanation for a clinically important disparity - one that has been dismissed or minimized for decades. "The difference in pain between men and women has a biological basis," Laumet said. "It's not in your head, and you're not soft. It's in your immune system." That framing matters for how clinicians approach and validate women's pain, independent of any therapeutic advance that may eventually follow.