In 1990, the US National Institutes of Health established the Office of Research on Women’s Health — not because women’s health was being well-served by the existing system, but because a congressional investigation had found the opposite. Women were systematically excluded from clinical trials. The drugs, procedures, and treatments developed through those trials were then applied to women based on male data. The medical system was, in significant respects, practicing medicine on women using knowledge it had derived entirely from men.

The situation has improved, but the improvement is partial, slow, and frequently overstated. The gender health gap remains one of the most significant and least discussed inequities in contemporary healthcare.

The Research Gap: How It Happened and What It Means

The exclusion of women from clinical research was not primarily malicious. It was the accumulated effect of several decisions that each seemed reasonable in isolation. Women were excluded from many trials after thalidomide — a drug given to pregnant women in the 1950s and early 1960s that caused severe fetal deformities — on the grounds that women of childbearing potential represented an unacceptable risk to fetuses. The intention was protective. The effect was to generate a body of medical knowledge based almost entirely on male biology.

The assumption underlying this was that male biology was the default and female biology was a variation. If a drug worked in male subjects, it would work in women — perhaps at a different dose, but through the same mechanisms. This assumption has been repeatedly shown to be wrong.

Women metabolize many drugs differently than men. The half-life of common medications is different; the effective dose is different; the side effects are different. A 2020 study in the journal Biology of Sex Differences found that across 86 different drugs approved by the FDA, adverse reactions in women were almost twice as common as in men — partly because dosing recommendations were based on male data and failed to account for sex-based differences in drug metabolism.

Ambien (zolpidem) is one of the most cited examples. The FDA approved ambien in 1992 based on trials that included far more men than women. More than a decade later, it became clear that women were experiencing “morning-after” impairment at rates much higher than men — they were falling asleep at the wheel, having accidents. In 2013, the FDA required the recommended dose for women to be halved. The drug had been on the market for over 20 years at the wrong dose for half its users.

The Symptom Presentation Problem

The second major dimension of the gender health gap is how symptoms present differently in women and how these differences are handled by clinicians.

Heart disease is the leading cause of death for women in most developed countries, killing more women than all cancers combined. Yet the classic presentation of heart disease — the crushing chest pain radiating to the left arm that is taught in medical school and depicted in popular culture — is primarily a male presentation. Women are more likely to present with what are called “atypical symptoms”: nausea, jaw pain, back pain, extreme fatigue, shortness of breath without chest pain.

Research consistently finds that women presenting with these symptoms are less likely to receive cardiac workup, more likely to have their symptoms attributed to anxiety or other psychological causes, and more likely to be sent home without appropriate treatment. A 2019 study in the European Heart Journal found that women were 50% more likely than men to be misdiagnosed following a heart attack.

Autoimmune diseases — conditions in which the immune system attacks the body — are another area of significant disparity. Women constitute roughly 80% of autoimmune disease sufferers, yet these conditions are still poorly understood, often underdiagnosed, and sometimes dismissed. Conditions like lupus, multiple sclerosis, rheumatoid arthritis, and fibromyalgia affect women predominantly, receive research funding disproportionately small relative to their burden, and are more likely to be attributed to psychological causes during the diagnostic journey.

A 2009 study found that women with chronic pain conditions were more likely to be prescribed sedatives and less likely to be prescribed pain medication than men presenting with equivalent pain levels — a finding consistent with the broader pattern of women’s reports of physical symptoms being treated as psychological rather than biological.

Endometriosis: A Case Study in Neglect

Endometriosis — a condition in which tissue similar to the uterine lining grows outside the uterus — affects approximately 10% of women worldwide, roughly 190 million people. Its primary symptom is severe pelvic pain, particularly during menstruation. It is associated with infertility, significant impacts on quality of life, and in some cases, damage to organs.

The average time from symptom onset to diagnosis is 7 to 10 years in most Western countries.

This extraordinary diagnostic delay is not a mystery: research has identified its causes clearly. Women reporting severe menstrual pain have historically been told this is normal and are frequently dismissed without diagnostic workup. Menstrual pain that is severe enough to prevent normal function is pathological — this is established — but the cultural normalization of female pain, and specifically menstrual pain, means women’s reports are often not taken seriously.

Definitive diagnosis of endometriosis requires laparoscopy — a surgical procedure — which has historically been prescribed conservatively, meaning that the diagnostic pathway is both delayed and invasive. Research into non-surgical diagnostic methods has progressed slowly. Research into causes, prevention, and better treatment has been underfunded relative to the disease burden.

In 2022, the WHO recognized endometriosis as a significant global health issue and called for accelerated research and improved diagnostic pathways. The recognition came decades after the condition’s scope was established. What changed was not the science but the advocacy — the growing number of women refusing to accept that their pain was normal, seeking diagnoses through multiple specialists, and organizing publicly for research funding.

The Menstrual Cycle and Medical Research

For decades, the variability introduced by the menstrual cycle was given as a reason to exclude women from clinical research — the hormonal fluctuations made data messier. This decision had the effect of ensuring that one of the most important physiological processes in half the population was systematically excluded from the research enterprise.

The practical consequences of this exclusion are far-reaching. We have relatively limited understanding of how common medications interact with the menstrual cycle. We have limited understanding of how conditions that are not specifically reproductive are affected by hormonal variation across the cycle. We know that the immune system varies across the cycle — which has implications for autoimmune disease, vaccine response, and infection susceptibility. The scientific investigation of these variations is still in early stages.

The work of researchers like Stacy Sims, who has studied female athlete physiology, has demonstrated in sports science what is true more broadly: the menstrual cycle creates meaningful variations in physiology that have practical implications for training, performance, and health. The advice given to women based on male-derived research is systematically suboptimal for female bodies.

What Women Need to Advocate For

The gender health gap requires structural change — more women in medical research, more funding for women’s health conditions, requirements that clinical trials be adequately powered to detect sex-based differences in outcomes. These are policy demands that require collective action.

But individual women navigating the current system need to be equipped with specific knowledge.

Know your family history. Cardiovascular disease, cancer, and autoimmune conditions have genetic components. Knowing your family history allows you to have informed conversations about screening and risk.

Document your symptoms specifically. Vague symptom reports are more easily dismissed. The severity, frequency, duration, and functional impact of symptoms — documented over time, if necessary — are harder to dismiss than a single verbal report.

Seek specialist referral when primary care does not produce answers. The diagnostic delays for conditions like endometriosis, PCOS, and autoimmune diseases often reflect the limitations of generalist training, not the absence of available diagnosis. Specialists see patterns that generalists may not recognize.

Ask about sex-specific data. “Are there sex-based differences in how this medication works or in the research underlying this recommendation?” is a legitimate clinical question. Increasing numbers of clinicians will have answers; others will be prompted to look for them.

Trust persistent symptoms. The research on women being dismissed for serious symptoms consistently finds that women with conditions including heart disease, endometriosis, cancer, and autoimmune disease had often raised concerns multiple times before receiving appropriate investigation. Persistence, which should not be necessary, is sometimes necessary.

The Clinicians Doing It Differently

It is worth noting that the gender health gap is not a conspiracy of individual misogynist clinicians. It is a systemic problem — produced by research gaps, training gaps, time pressure in clinical settings, and cultural assumptions about which symptoms are serious — that affects clinicians who are themselves committed to good care. Individual clinicians who become aware of the research disparities frequently change their practice.

There is also a growing body of clinicians — particularly, though not exclusively, women — who are specifically focused on sex-based medicine: understanding how diseases present, progress, and respond to treatment differently in female patients. These clinicians exist across specialties. Finding them, where possible, is a form of advocacy for one’s own health.

The medical system can change. The research on cardiovascular disease in women has improved dramatically since the 1990s, partly as a result of focused advocacy and partly because female patients and female researchers kept insisting on it. The same trajectory is visible in other areas. Slow, partial, insufficient — but moving in the right direction.

The direction will move faster with more pressure.

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