Women are also better able to detect small gradations in pain stimuli. And they respond differently to certain opioid — painkilling — drugs. (It’s not clear whether men and women differ in sensitivity to cancer pain.)
But it’s only recently that researchers have begun to study the exact genetic, physiological, hormonal, and psycho-social factors that may underlie these sex differences. In part, that’s because pain researchers have been hampered by one — rather shocking — fact: Most basic pain research is still done in male mice and rats.
This has been “a catastrophe,’’ says McGill University pain geneticist Jeffrey Mogil, adding that the old rationale that menstrual cycles make females too difficult to study is bogus. Men and women, in fact, can be so different in the way their nervous systems process pain that someday there may be “pink pills for women, and blue pills for men,’’ he says. The lopsided research exists solely because of “inertia,’’ he adds.
Others agree, among them Dr. Roger B. Fillingim, lead author of an exhaustive 2009 review of sex and pain research published by the American Pain Society. In that paper, Fillingim, a pain researcher at the University of Florida, notes that while the National Institutes of Health now require routine inclusion of both sexes in human studies, much animal research “continues to eschew females.’’ Given that pain is mainly a female problem, he adds, this means research “that excludes females is incomplete at best and invalid at worst.’’
Luckily, this shutout is not total, and of course, some human research does specifically address sex differences — with complex, and fascinating results.
