Studies have shown that women's bodies are naturally more sensitive to pain.

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Different Bodies, Different Pain Responses

When it comes to coping with pain, women are the more voluble sex [source: Kritz]. Men, on the other hand, tend to bear their burdens quietly. Some researchers attribute that pattern to social conditioning; gender roles permit girls to cry and express their feelings more openly than boys, who are expected to keep a stiff upper lip.

But a study at the University of Florida debunks this social theory. Psychologists offered male and female participants a certain amount of money depending on how long they were able to hold their hands in an ice water bath. The researchers hypothesized that the monetary reward would eliminate any social gender norms, making both sexes equally motivated to hold their hands in the freezing water for as long as possible [source: Dye]. However, even with the cash incentive, the men still outlasted the women.

Psychologists also theorize that women's innate mindfulness might contribute to heightened pain sensitivity. In general, women are more attuned to how they feel physically, which might mentally predispose them to noticing pain. Females also have a higher incidence rate of anxiety and depression, which researchers have linked to greater pain sensitivity in women -- but not in men [source: Toomey].

Furthermore, research indicates that female bodies naturally respond to painful stimuli more intensely than males'. In one experiment, women's pupils dilated faster than men's when uncomfortable pressure was applied to their fingers. Since pupil dilation is a physiological response to pain that's controlled by the autonomic nervous system, the study demonstrated that the females' keener pain responses are beyond conscious control [source: Toomey]. And to top things off, fluctuating female hormones can either dampen or amplify pain on any given day.

For the women in the ice water study, research indicates that the time of the month could've impacted their pain tolerance. Although scientists haven't been able to quantify the precise effects of the menstrual cycle on pain, studies have drawn a correlation between estrogen and pain thresholds in women. Specifically, when estrogen levels crest, the female body responds more effectively to pain, releasing a greater amount of soothing endorphins and enkephalins [source: Dye]. This estrogen-pain connection could explain why postmenopausal women with low estrogen suffer more from chronic painful conditions, such as fibromyalgia [source: Kritz].

Due to the differences between how male and female bodies process pain, some scientists have started taking a gender-specific approach to formulating painkillers.