Whether it's Joan of Arc — executed in part for routinely wearing male clothing — or the Native American "berdache" — gender-variant people revered in certain tribes as "twin spirits" — the world has a long history of gender roles being blurred.

Some cultures accept people whose gender identity doesn't match their anatomical sex. A tribe in Samoa, for example, has a third gender made up of men who perform tasks otherwise reserved for women. But in America and most parts of the world, the binary system of gender identification is not friendly to those who don't fit in.

"One thing that people feel they can hold on to is that if, on the day you're born, they look between your legs and say 'male' or 'female,' then it's expected you'll behave in a masculine or feminine way," said June LaTrobe, transgender liaison for the Center on Halsted an LGBT community center in Lakeview. "But if you say, 'Regardless of what my genitalia may look like, that's not how I feel about myself,' then it can get to be just confusing. It's just not part of what many people have in their database."

That's in large part because traditional gender roles are imparted on people at a young age.

"We teach gender roles mainly through shame," Ettner said. "Children learn quickly that there are certain feelings they can't express or they will be punished or shamed or ridiculed. But developmentally, gender variance is something that occurs very early in life."

Experts like Ettner agree that the term "transgender" means, in essence: people who want to spend all or part of the time presenting themselves in a gender other than the one they were assigned at birth. That said, sex researchers have found that there is tremendous diversity in the transgender community, so much so that many now view gender identity not simply as "male" or "female," but as points on a spectrum between masculine and feminine.

Some transgender people are transsexual, meaning they want to alter their primary and secondary sex characteristics, anything from taking hormones to having sexual-reassignment surgery. On the other end of the spectrum, a transgender person who is anatomically male might identify partially as a woman and need only to occasionally dress in women's clothing in order to feel complete.

People diagnosed with gender identity disorder have often gone for years battling depression and emotional stress, along with feelings of being disingenuous. Therapists have found that these people, in most cases, can find psychological relief only by living in the gender with which they identify.

"For an adult with real gender dysphoria, it's unlikely that they're going to be comfortable living in their physical sex," said Richard Carroll, associate professor of psychiatry and behavioral sciences at Northwestern University's Feinberg School of Medicine. "The crucial step is for the individual to take some time to examine the options in a thoughtful way."

For Carmichael, who was serving as a woman in the Army National Guard, the time to think about gender identity came during the Iraq War. When a close friend was badly injured, the thin line between living and dying prompted him to address the confusing feelings that had plagued him since childhood: "I had hard questions to ask myself. And I did it."

While still in Iraq, Carmichael began, in his head, referring to himself using male pronouns. It felt right. After the war, he returned to Chicago and spent time reading extensively about what it meant to be transgender. He considered his lifelong journey — being a young girl who felt awkward in traditionally feminine roles; coming out in high school as a lesbian, hoping the disconnect he felt was a matter of sexuality; then recognizing that the problem was actually one of gender identity.

When Carmichael decided to transition and began living his life fully as a man, he at last felt right.

"I'm very comfortable being a trans man," said Carmichael, who now does respite work for a family who has a child with autism. "I'm sort of reveling in the idea of finally being content."

Alice Dreger, professor of clinical medical humanities and bioethics at Northwestern, said this kind of outcome is common and demonstrates what it takes for a transgender person to find physical and psychological peace.

"People who are transgender do much better after they have the interventions they need," Dreger said. "The regret rate in sex-change procedures is very, very low."