Intersex

Intersex covers variations in chromosomes, gonads, hormones or genitals that do not fit typical binary definitions of male or female. It belongs in this vertical for one reason only: it is routinely listed as a gender and is not one. Intersex is a fact about the body. Gender identity is a separate question, and most intersex people answer it with man or woman, exactly as most other people do.

Definition & scope

The category covers dozens of distinct conditions with little in common clinically — androgen insensitivity syndrome, congenital adrenal hyperplasia, chromosomal variations such as 47,XXY, and others. Some are apparent at birth, some at puberty, some never without testing. What unites them is a definitional judgement rather than a shared biology, which is why the boundary of the category is contested (see prevalence below).

Intersex is not the same as transgender. A trans woman is a woman recorded male at birth; an intersex person has a body that does not fit the categories the recording uses. The two can coincide but do so no more often than chance would suggest. Conflating them is the single commonest error, and it is not a small one — the two groups have different histories, different medical relationships and largely different political demands.

The term the medical literature increasingly uses is differences of sex development (DSD), introduced in 2006. Many intersex people reject it as re-pathologising, preferring intersex or variations in sex characteristics; the naming dispute is live and this entry uses both.

History & origins

The modern history is mostly a history of surgery.

• 1950s–1960s: the psychologist John Money's protocol at Johns Hopkins established early surgical assignment as standard care, on the theory that gender identity is set by rearing if the body is made to match early enough.
• 1966–1970s: the David Reimer case, in which Money's protocol was applied to a boy after a circumcision accident, was reported as a success for decades and was in fact a catastrophic failure — a fact that emerged publicly only in 1997 and did more than any argument to discredit the model.
• 1993: the Intersex Society of North America is founded, and intersex people begin organising against non-consensual infant surgery.
• 2006: the Chicago Consensus Statement introduces disorders/differences of sex development and revises clinical guidance.
• 2010s–2020s: several jurisdictions restrict or ban medically unnecessary surgery on intersex infants; UN human-rights bodies characterise the practice as a rights violation.

In practice

The central issue for intersex advocacy is consent and its timing. Cosmetic surgery performed on infants — before the person can express a gender identity or consent to an irreversible procedure — remains legal in most jurisdictions and is the practice the movement was formed to stop.

The second issue is disclosure. A recurring theme in intersex testimony is discovering one's own medical history in adulthood, sometimes by accident, because clinicians advised parents to withhold it. Both issues are about the handling of the fact rather than the fact itself.

Psychology

Intersex variation is not a psychological condition and no diagnostic manual treats it as one. The DSM-5 and the ICD-11 address gender-related distress separately, and the ICD-11 removed gender incongruence from its mental-disorders chapter in 2019.

The research literature that exists concerns outcomes of childhood treatment, and it does not support the Money-era model: gender identity is not reliably produced by early surgical assignment and rearing. The psychological harms reported by intersex adults cluster around secrecy, irreversible procedures they did not consent to, and repeated medical examination in childhood — around handling, again, rather than around bodies.

Prevalence & culture

How common is being intersex?

This is the most disputed number in the whole vertical, and the dispute is definitional rather than empirical.

The widely circulated 1.7% comes from Blackless, Fausto-Sterling and colleagues (2000) in the American Journal of Human Biology, who surveyed the medical literature from 1955 onward and summed the reported frequencies to 1.728 cases per 100 births. It uses a broad definition that counts any deviation from a Platonic ideal of male or female — including chromosomal variations such as 47,XXY and 45,X and late-onset congenital adrenal hyperplasia, most of which are not apparent at birth and are not treated as intersex by most clinicians.

Leonard Sax's 2002 reply in the Journal of Sex Research argued the term keeps its meaning only if restricted to conditions in which chromosomal sex is inconsistent with phenotypic sex, or the phenotype is not classifiable as either. On that definition the figure is 0.018% — roughly a hundredfold lower.

Both numbers are arithmetically correct. They count different things, and quoting either without its definition is the error. The figure recorded on this entry is Sax's narrower one, because it matches the sense in which "intersex" is used in the rest of the article; the broad figure is the right one for questions about sex-characteristic variation generally.

For scale, Gallup's 2025 survey puts transgender identification at 1.3% of US adults and the Williams Institute at 0.8% — figures that sit between the two intersex estimates, which is worth noticing before the popular claim that intersex people are "as common as redheads" is repeated. That claim rests on the broad definition and is routinely quoted without it.