The difficulty may continue into adulthood. While some men with Asperger’s marry and have families, women almost never do, psychiatrists observe. A 2004 study by two prominent British researchers, Michael Rutter and Patricia Howlin, followed 68 high-functioning autistics over more than two decades. The group included only seven women, too small a sample to reach solid conclusions about gender differences, Rutter and Howlin caution. But 15 men — 22 percent of the sample — rated “good” or “very good” for educational attainment, employment, relationships and independent living, while no women did. Two women rated “fair,” compared with 11 men, and the other five women were counted as “poor” or “very poor.” None had gone to college. None reported having friends or living on their own. Only one had a job. Undermined by anxiety and depression, women with autism appear to be more often confined to the small world of their families.

When Caitlyn started kindergarten and didn’t play normally with other kids, her mother, Juli, thought it was because she hadn’t gone to preschool. The first warning of real trouble came from the first-grade gym teacher, who told Juli that Caitlyn exposed herself to the class. Caitlyn is overweight, and she has always been private about her body. Juli couldn’t imagine her daughter taking off her clothes in public, and when she asked what had happened, Caitlyn said another girl had pulled down her pants. “Caitlyn stood there mortified,” Juli says. “But she couldn’t express that to the teacher.”

Caitlyn lives with her mother, her older sister, the girls’ great-grandparents and a pair of poodles in Farmington, outside of Salt Lake City. (Her father died before she was 2.) Until second grade, Caitlyn had a neighborhood friend with whom she went to school. Other than that, she was often alone in class. Her teachers were frequently frustrated with her inability to work and play in groups. But she connected with a few adults — in fifth grade, one class aide took her horseback riding, and the school librarian gave Caitlyn her own copy of “Spindle’s End,” a retelling of “Sleeping Beauty,” “because she said I helped her so much,” Caitlyn remembers.

Contrary to the Asperger’s stereotype, Caitlyn struggles in math but tests in the highly gifted range in reading and writing. This is another sex difference that Lord sees among her patients. “I don’t have any real data, but a lot of high-functioning girls are real readers — not great on subtleties, but they like fantasies and the ‘Baby-Sitters’ series,” she says. “The boys are much less so.”

In elementary school, Caitlyn went to special-education classes for math and social skills. At 11, as other girls began to slip out of reach, Asperger’s was diagnosed. The shift a year later to junior high for seventh grade was a jolt. By the second week of school, a few boys were mocking Caitlyn’s weight and calling her weird while other kids laughed. “No one would sit by me at lunch,” Caitlyn says. Girls told her that they didn’t want her to be in their reading group. Caitlyn did her homework, but she was too anxious to walk to the front of the room to turn it in. At home, her neighborhood friend no longer came out to play.

In the winter, Caitlyn switched from a special-education math class into a mainstream one, and the kids in her new class made her miserable. For days she refused to go to school. She told Lainhart: “No one likes me at lunch. I’m very sad.” (With Juli’s and Caitlyn’s permission, I read Lainhart’s notes on Caitlyn’s treatment.) After a huge outburst of anger at home, Caitlyn told her mother that she wanted to die. At her next appointment with Lainhart, she said: “I listen to people’s conversations during free time in science. They talk about live games, R-rated movies, outfits. I feel left out.” Caitlyn told Lainhart about two dreams. In one, her school had a bridge running through it, and she kept falling off. In the second, she was in the lunchroom throwing a party; no one came. Lainhart says that while boys are aware of rejection and bullying, in her experience they are not hurt by it to the extent that some girls are. “I have rarely had a male patient with autism become suicidal or express such intense emotional pain,” she says.

Caitlyn has never hit another child. But at school, her retorts to her peers — “I yelled at a . . . little bimbo. They yelled at me,” she told Lainhart during one appointment — pushed them further away. With Lainhart’s help, Juli persuaded the school to let her daughter eat lunch in a classroom rather than in the cafeteria. Still, Caitlyn’s grades dropped from A’s and B’s to D’s and F’s. Her anxiety level spiked, and her sadness bloomed into depression.