Breast cancer typically strikes after the age of 50. But of the 200,000 women diagnosed every year, 11,000 are under 40–and their youth isn’t necessarily an advantage. A landmark study published last week by researchers at Boston’s Brigham and Women’s Hospital found that young women tend to be more negatively affected by a breast-cancer diagnosis, both physically and psychologically, than middle-aged or elderly women. For young single women, especially, the emotional effects can be excruciating. One day they’re embracing their sexuality and looking for love. The next, they may be losing a breast, their reproductive future and their self-esteem. “Every now and then I’ll look in the mirror and think, ‘Ooh, I used to be hot’,” says Suellen Bennett, 35, who had a mastectomy in December. “What happened to me?”

The problems begin with diagnosis. Mammograms don’t work well in dense young breast tissue. And even when women find a lump themselves, doctors often wait to do a biopsy, assuming it’s nothing more than a benign cyst. “Some women have to fight to get tested,” says Beth Leibson-Hawkins, author of the book “I’m Too Young to Have Breast Cancer!” due out this fall. As a result, young women are more likely to be diagnosed at a later stage than older women. On top of that, hormone differences often make their tumors more aggressive.

Chemotherapy is good for killing cancer, not so good for feeling beautiful. Side effects can include nausea, hair loss and premature menopause, which can trigger hot flashes and a nose-diving sex drive. The upshot for many single women: social hibernation. “The last thing you want to do is be at a bar,” says Erin Weir, 34, who had a double mastectomy two years ago after doctors found cancer in both breasts. “You’re more worried about if you’re going to live or die.” Jennifer Wolfe, 37, recalls the night her hair started falling out before a date. She answered the door in tears. “I always thought of myself as an attractive person,” says Wolfe. “Cancer completely changed that.”

For many of these women, nothing is scarier than intimacy. When Roberta Schwartz had a mastectomy at 27, she thought, “Who the hell is going to look at me again? How can anybody touch me?” Not all men are scared off. Schwartz, who cofounded YSC to raise awareness about breast cancer in young women, met a guy named Lee in the middle of chemo. “All I remember is feeling like ‘I’m going to puke on you’,” she says. She was floored when he called the next day. Schwartz, now 34, resisted becoming intimate–“Pulling off my shirt was the hardest thing” –but Lee told her he cared more about her soul than her scars. Today, seven years later, they’re married with two kids.

The ultimate concern for many young women is fertility. Some couples now freeze embryos before treatment. But the procedure requires hormone shots, which doctors worry could fuel the cancer. Fortunately, researchers are now monitoring the effects of treatment on reproduction and testing new ways to restore fertility–including freezing slices of ovarian tissue–to increase the odds of baby-making.

Two months ago Suellen Bennett celebrated her last round of chemotherapy. She is now stronger than ever–and determined to live life with all the spirit she had before her diagnosis. “Thirty-five is way too young to not get my groove back,” she says.