Even when male and female patients show similar levels of suffering in their facial expressions, physical pain among women is not taken as seriously, a new psychology study suggests.

Not only does the average observer tend to underestimate the intensity of chronic shoulder pain in women compared to men, but the findings reveal observers are also more likely to suggest psychotherapy as a treatment.

The way our faces respond to pain is one of the most obvious signs of suffering in people, and yet previous studies have shown our perceptions of pain expressions carry a gender bias.

Women are often thought to be more sensitive to pain or more prone to exaggerating their suffering, while men are assumed to be more stoic, with a higher threshold for agony. Neither account, it seems, is trustworthy.

This has led to some contradictory results in previous research. Sometimes, for instance, female patients are judged as being in more pain because they often report and show their pain more freely than male patients. As a result, female patients in some studies appear to be given more pain medication.

In many other cases, however, female patients are assumed to be exaggerating their pain. As such, their facial expressions might be dismissed as a valid measure of their suffering, and they could be given less pain medication as a result.

Biased ideas about facial expressions may very well play a role in this discrepancy, but even when expressions of pain are similar, the new research suggests there are still more biases at play.

Gender role expectations about pain endurance and our willingness to report pain could also be creating an obstacle to effective pain care, both at home and possibly in the clinical setting.

"The more willing perceivers believed women are to report pain than men, the less pain they perceived female patients to be in," the authors explain.

"Importantly, these biases were observed while participants viewed actual patients in genuine clinical pain, and when controlling for pain facial expressiveness and patients' self-reported pain."

In the first experiment of the study, 50 everyday participants in the United States, not from the healthcare sphere, were shown a series of short video clips, each depicting a real patient's face in chronic shoulder pain.

No matter whether the facial expressions were equal in intensity or not, male and female viewers both rated the pain of female patients as lower. On a scale of 0 to 100, from absolutely no pain to the worst pain possible, male patients were given a pain score more than two points higher, on average, than their female counterparts.

The second experiment expanded the first part of the study among 197 participants – three of which were healthcare workers – and more than half of which had at least one chronic or acute pain condition of their own.

After each clip, the video was paused on a neutral expression, and participants were again asked to estimate the patient's pain from 0 to 100.

Observers were also asked to imagine they were the patient's doctor and were asked three questions about treatment options: "If you were to prescribe pain medicine, what dose would you prescribe to this patient?"; "If you were to prescribe psychotherapy, how many sessions would you prescribe?"; and "What do you think would help the patient more, pain medicine or psychotherapy?".

(The dosages and prescriptions were laid out on a scale of 0 to 100, as most people in the study did not have a healthcare background.)

Running a multi-level model of these results, researchers found the second experiment largely matched the first. After controlling for patients' self-reported pain and level of pain facial expressiveness, female patients were again perceived as being in less pain overall.

Plus, while the observers elected to prescribe medicine to both male and female patients, when forced to choose between medicine and therapy for their patients, the female patients were 4 percent more likely than male patients to be prescribed psychotherapy, which is a significant difference.

At the end of the second experiment, participants were asked to complete a questionnaire, which ranked their gender bias on the issue of pain.

This final questionnaire has helped provide some explanation for the study's results. In the end, those participants who believed women were more likely to report pain than men estimated female patients were in less pain than male patients and prescribed female patients less medication.

At the same time, those who thought men could endure more pain (and also were less willing to report it) estimated pain in male patients was higher and prescribed this group more pain medicine.

In the end, it seems the average observer is using their assumptions about gender to explain the symptoms of pain they see instead of taking the suffering at face value.

This has ultimately caused the majority of participants in the study to mis-estimate a patient's self-reported pain to the male patients' benefit and the female patients' detriment.

"Together, these findings suggest that women's pain is underestimated compared to men's and perceived to benefit more [from] psychotherapy, and that perceivers' pain-related stereotypes may be a source of these pain estimation and treatment biases," the authors conclude.

While the results of this study might not extend equally to people who are more familiar with signs of physical pain (such as healthcare workers), the authors say their findings indicate "the average participant shows reasonably strong gender bias and that other factors such as additional pain stereotypes, or perceptual biases likely contribute to this bias".

The study was published in The Journal of Pain.