The first nationwide study to break down domestic violence rates by self-identified sexual orientation has found that lesbian and bisexual women are at higher risk than straight women, with bisexual women facing especially high rates.

The study [PDF], conducted by the CDC in 2010 and released Friday, found that 35% of straight women had experienced rape, physical violence, or stalking by a partner at some point in their lives. But 43.8% of lesbian women had experienced one of the three, as had a full 61.1% of bisexual women. Researchers interviewed a total of 9,709 women — 96.5% of them identified as straight, 2.2% as bisexual, and

1.3% as lesbian.

Bisexual women were also the most likely to have been raped by anyone, partner or not — 46.1% of them had experienced rape at some point, compared with 13.1% of lesbian women and 14.7% of straight women. And they were more likely to report that domestic violence had negatively impacted their lives — 57.4% of bisexual women who'd experienced violence said they also suffered aftereffects like missing work or having symptoms of post-traumatic stress disorder. Only 33.5% of lesbian women and 28.2% of straight women said the same.

Most domestic violence against bisexual women appeared to be committed by male partners — 89.5% of bisexual participants who'd experienced such violence said the only perpetrators had been male.

Mikel Walters, a behavioral scientist for the CDC, says the study didn't examine the reasons why lesbian and bisexual women might experience especially high rates of violence. "Hopefully this research will spur more research" into causes, she said.

A 2011 study found that bisexual women were at greater risk of depression and anxiety than women who were straight or gay, a result the study author attributed to stigma against bisexuality. "There tends to be this expectation or standard that a person picks one sexual identity and sticks with it. I think there's a lot of misunderstanding about bisexuals," the author told Huffington Post UK.

Whether stigma makes it harder for bisexual women to get or seek help if they're in abusive relationships is beyond the scope of the CDC study. The researchers did ask women whether they needed housing or victim's advocate services or called a crisis hotline after experiencing violence, but the numbers of lesbian and bisexual women who said they had needed these forms of help were too small to be statistically significant.

"We hope that these findings will be used by policymakers and practitioners to expand services to everyone who experiences intimate partner violence," says Walters. "Intimate partner violence, sexual violence, and stalking are widespread, and they affect every type of person, regardless of their relationship or sexual orientation."