Two well-documented gaps in the medical evidence base overlap here.
The first is the historical underrepresentation of women in clinical research, which has been extensively documented and partially corrected through regulatory requirements over the past three decades.
The second is the underrepresentation of children and adolescents, driven by ethical caution about research on minors and by commercial disincentives to conduct paediatric trials.
Adolescent girls fall in the intersection, and the evidence base for them is correspondingly thin.
What the exclusion produced
For a long period, a great deal of clinical research was conducted on adult male subjects and generalised to everyone.
The stated reasons included concern about effects on potential pregnancy and a desire to avoid hormonal variation as a confounding variable. The second reason is worth pausing on: it treats a characteristic of half the population as noise to be excluded rather than as a variable to be studied.
Regulatory requirements have since improved inclusion substantially. But analyses of clinical trial reporting continue to find that results are frequently not disaggregated by sex, meaning that even where women are included, differences may not be detectable in the published analysis.
The dosing consequence
The clearest downstream effect is in drug dosing.
Analyses of adverse drug reactions have consistently found higher rates in women than men. Proposed mechanisms include differences in body composition, hepatic metabolism, renal clearance and, for some drugs, differences in the fraction of drug reaching circulation.
There are documented cases in which recommended doses of widely used medications were revised downward for women after post-marketing data showed different pharmacokinetics.
For adolescents, the picture is worse, because paediatric dosing is frequently extrapolated by weight from adult data. Weight-based extrapolation assumes that the only relevant difference is size, which is not generally true — organ maturity, enzyme activity and body composition all differ.
Conditions where the gap is most visible
Cardiac presentation. Symptoms of cardiac events differ between men and women, with the "classic" presentation derived largely from male patients. Studies of diagnostic outcomes have found longer times to diagnosis and differences in treatment intensity for women presenting with cardiac symptoms, and the effect appears larger in younger patients.
Autoimmune conditions. Several are markedly more common in women and have long average diagnostic delays. The reasons are complex — these conditions are genuinely difficult to diagnose — but the pattern of diffuse, multi-system symptoms being attributed to stress or anxiety appears repeatedly in patient-reported experience research.
Pain conditions. Studies of pain assessment have found differences in how pain reports are received and treated, with several finding that women's pain is less likely to be treated with analgesia and more likely to be attributed to psychological causes.
Conditions specific to female physiology. Research funding analyses have found conditions such as endometriosis historically receiving funding disproportionately low relative to their prevalence and burden.
Adolescence adds its own problem
Adolescent patients face a distinct set of difficulties beyond the evidence gap.
Symptoms are frequently attributed to normal developmental change. Since adolescence genuinely does involve substantial physiological change, this is a reasonable prior — and it produces a systematic tendency to under-investigate.
Consultations frequently occur with a parent present, which affects disclosure of symptoms relating to sexual health, mental health and substance use.
Adolescents are often less able to advocate for themselves, less familiar with how to describe symptoms in medically useful terms, and more likely to accept a dismissive answer.
And there is a documented tendency for adolescent girls' physical symptoms to be attributed to anxiety at higher rates than boys' — a finding that appears in several studies of paediatric presentations.
What is improving
Regulatory requirements for sex-disaggregated reporting have strengthened, and several major funders now require it as a condition of funding.
Sex-specific analysis is becoming more standard in trial design rather than being left to secondary analysis.
Adolescent-specific clinical guidelines have expanded in a number of areas, particularly mental health and reproductive health.
Progress is real and slow, and the evidence base takes decades to fill because it requires new trials rather than reanalysis.
What a patient can do
Ask whether the recommendation is based on evidence from a population like her. This is a reasonable clinical question and most clinicians will engage with it seriously.
Keep a symptom record with dates, severity and circumstances. Documentation shifts a consultation from recollection to evidence, and it addresses the specific problem of symptoms being described vaguely under time pressure.
Ask for the differential — what else could this be, and what would rule it out. This is more productive than disputing a diagnosis directly.
Request time without a parent present where relevant. Most systems permit this and most adolescents do not know it.
And where a symptom is persistent and has been attributed to stress without investigation, asking for the investigation explicitly is reasonable. The attribution may well be correct; the point is that it should be a conclusion rather than a default.