TO the list of differences between men and women, we can add one more: the drug-dose gender gap. Doctors and researchers increasingly understand that there can be striking variations in the way men and women respond to drugs, many of which are tested almost exclusively on males. Early this year, for instance, the Food and Drug Administration announced that it was cutting in half the prescribed dose of Ambien for women, who remained drowsy for longer than men after taking the drug.

Women have hormonal cycles, smaller organs, higher body fat composition — all of which are thought to play a role in how drugs affect our bodies. We also have basic differences in gene expression, which can make differences in the way we metabolize drugs. For example, men metabolize caffeine more quickly, while women metabolize certain antibiotics and anxiety medications more quickly. In some cases, drugs work less effectively depending on sex; women are less responsive to anesthesia and ibuprofen for instance. In other cases, women are at more risk for adverse — even lethal — side effects.

These differences are particularly important for the millions of women living with chronic pain. An estimated 25 percent of Americans experience chronic pain, and a disproportionate number of them are women. A review published in the Journal of Pain in 2009 found that women faced a substantially greater risk of developing pain conditions. They are twice as likely to have multiple sclerosis, two to three times more likely to develop rheumatoid arthritis and four times more likely to have chronic fatigue syndrome than men. As a whole, autoimmune diseases, which often include debilitating pain, strike women three times more frequently than men.

While hormonal, genetic and even environmental factors might influence the manifestation and progression of autoimmune diseases, we don’t yet know the reason for this high prevalence in women.

Pain conditions are a particularly good example of the interplay between sex (our biological and chromosomal differences) and gender (the cultural roles and expectations attributed to a person). In 2011, the Institute of Medicine published a report on the public health impact of chronic pain, called “Relieving Pain in America.” It found that not only did women appear to suffer more from pain, but that women’s reports of pain were more likely to be dismissed.

This is a serious problem, because pain is subjective and self-reported, and diagnosis and treatment depend on the assumption that the person reporting symptoms is beyond doubt.

The oft-cited study “The Girl Who Cried Pain: A Bias Against Women in the Treatment of Pain” found that women were less likely to receive aggressive treatment when diagnosed, and were more likely to have their pain characterized as “emotional,” “psychogenic” and therefore “not real.”

Instead of appropriate care for physical pain, this can lead to treatment for mental health issues that might not even exist. The situation is further complicated by the fact that antidepressants are absorbed differently in women and vary in effectiveness, depending on hormonal cycles.

The routine attribution of abdominal pain from conditions like appendicitis or gastrointestinal disease to gynecological problems can also delay or complicate the diagnostic process. A 2008 study published in the journal Academic Emergency Medicine, designed to gauge gender disparities among emergency room patients complaining of abdominal pain, found that even after adjusting for race, class and triage assessment, women were still 13 to 25 percent less likely than men to receive high-strength “opioid” pain medication. Those who did get opioid pain relievers waited an average of 16 minutes longer to receive them.

Conditions like fibromyalgia or chronic fatigue syndrome, for which definitive causes have not been identified and concrete diagnostic tests are not available, illustrate the problems associated with the perceived reliability of the female patient as narrator of her pain. Women are more likely to receive diagnoses of many of these more nebulous conditions — fibromyalgia, which affects about six million patients in the United States, is nine times more likely to be diagnosed in women than in men — and this discrepancy surely contributes to the widespread skepticism that still exists over the legitimacy of these disorders.

I AM a sufferer of pain and chronic disease. Like many, I’ve had physical symptoms (in my case, respiratory problems and infections) explained away as emotional. My freshman year in college, I was in the emergency room, flanked by machines and struggling to breathe while doctors lobbed questions at me: Why wasn’t I responding to the medication the way they expected I would? Was I just too anxious? Could I not handle stress, and was that making me sick?

I was 23 before I was given a correct diagnosis of a rare genetic lung disease called primary ciliary dyskinesia. I’d been sick since birth, but long diagnostic journeys are occupational hazards of living with conditions doctors don’t often see. Still, my journey was unnecessarily protracted by my doctors’ dismissal of my symptoms as those of a neurotic young woman.

For all the medical advances of the past few decades, we still know shockingly little about pain and how to control it. Sex-based research is a crucial part of understanding not just the underlying mechanisms of pain, but the most effective ways to treat it for men and women alike. The Institute of Medicine report found gaps in research, particularly in terms of effective treatments, as well as in the oversight of pain research. The report recommended that these problems be addressed and that strategies to resolve them be implemented by 2015.

Among those improvements must be a renewed focus on discovering why women respond differently to some drugs and diseases, as well as an emphasis on training physicians to better diagnose and manage women’s pain. A report by the Campaign to End Chronic Pain in Women found that inadequate physician training in diagnosing and treating just six pain disorders that affect women either exclusively or predominantly, including fibromyalgia and chronic fatigue syndrome, added as much as $80 billion a year to America’s health care bills.

Part of the reason the diagnosis and treatment of women’s pain lag so much is simply the pace of medical research itself, which is slow to move from publication to clinical practice. Unfortunately, if anything, changes in assumptions about gender evolve even more slowly.