Domestic violence occurs more frequently among same-sex couples than opposite-sex couples, according to a new review from Northwestern University.

Sometimes called intimate partner violence, domestic violence is physical, sexual, or psychological harm occurring between current or former intimate partners.

Previous studies, when analyzed together, indicate that domestic violence affects 25 to 70 percent of lesbian, gay and bisexual individuals. However, a lack of representative data and underreporting of abuse paints an incomplete picture of the true landscape, suggesting even higher rates. An estimated one in four heterosexual women experience domestic abuse, with rates significantly lower for heterosexual men.

"Evidence suggests that the minority stress model may explain these high prevalence rates," Richard Carroll, senior author of the study, said in a statement. "Domestic violence is exacerbated because same-sex couples are dealing with the additional stress of being a sexual minority. This leads to reluctance to address domestic violence issues."

Research concerning domestic violence began in the 1970s in response to the women's movement, but traditionally studies focused on women abused by men in opposite-sex relationships.

"There has been a lot of research on domestic violence but it hasn't looked as carefully at the subgroup of same-sex couples," Carroll said. "Another obstacle is getting the appropriate samples because of the stigma that has been attached to sexual orientation. In the past, individuals were reluctant to talk about it."

Carroll suggests that homosexual men and women may not report domestic violence for fear of discrimination and being blamed for abuse from a partner. They also may worry about their sexual orientation being revealed before they are comfortable with it.

Although there are mental services for people involved in abusive same-sex relationships are becoming more common, this population still faces obstacles in accessing help.

"We need to educate health care providers about the presence of this problem and remind them to assess for it in homosexual relationships, just as they would for heterosexual patients," Carroll said. "The hope is that with increasingly deeper acceptance, the stress and stigma will disappear for these individuals so they can get the help they need."

The review was published Sept. 4 in the Journal of Sex & Marital Therapy.