Considered a form of domestic and gender-based violence, honor killings often involve women murdered by family members to avenge shame brought by infidelity or other culturally unacceptable behaviors.
"It's a very unique kind of violence, because usually domestic violence is caused by husbands or partners, but this is often conducted by brothers or fathers," said Dr. Muazzam Nasrullah, who ran the study while at the Aga Khan University in Pakistan.
Now working as an Epidemic Intelligence Service officer with the Centers for Disease Control and Prevention, Nasrullah said the report is the first statistical study that attempts to quantify the problem since data about the practice are so difficult to collect. Nasrullah used local and national newspaper reports systematically compiled by the Human Rights Commission of Pakistan as the basis for his study.
Other sources of data, such as death certificates, often do not include specific enough information on the circumstances of the death, Nasrullah said.
A total of 1,957 incidents of honor killings were recorded over four years, the study reported. The majority occurred in response to alleged extramarital relations.
But Nasrullah said he is confident the results were lower than the actual number because not every event makes it into the media.
"The problem is much more than what is depicted in my paper," said Nasrullah.
Honor killings are not unique to Pakistan, and the World Health Organization estimates about 5,000 women are murdered by family members in the name of honor each year worldwide.
Dr. Claudia Garcia-Moreno, an adviser on gender violence at the World Health Organization, said honor killings are an extreme form of violence against women "which we see primarily in the Middle East and in parts of Asia, but in many ways they are not very different than some of the murders that are being documented in other places."
Women's sexuality and the cultural norms surrounding it are part of patterns of violence throughout the world, she said.
"From the public health perspective, we have been looking at: how do you stop some of these different forms of violence from happening in the first place?" said Garcia-Moreno.
But addressing these issues requires action on multiple levels, including having strong, enforced laws, as well as social messages that make it clear these types of violence are not acceptable - a difficult task when a practice is ingrained in a society.
Having reliable data about honor killings is an important starting point, said Garcia-Moreno, because many types of domestic violence are kept hidden by both perpetrators and victims.
"There is a saying that in order to make something count you have to count it," Garcia-Moreno said.
"Until relatively recently, some of these issues have been invisible. Issues of domestic violence were considered private, so in some ways part of the culture change is to start to name and to count what is happening."
One of the biggest challenges in trying to halt honor killings is their long tradition of being seen as a way of upholding the moral values of society, said T. Kumar, advocacy director for the Asia and Pacific region at Amnesty International.
Any lasting shift in how honor killings are viewed would have to come from the community itself, said Kumar. The pressure to maintain the practice is so great that in some instances, family members may feel they have no other options, despite not wanting to harm their child or sister, he said.
"Their respect in the community was tarnished by that family member so they want to regain that," said Kumar. "If you don't do it then you have been laughed upon."
While honor killings are illegal and considered murder in Pakistan, there are loopholes that often prevent full punishment for the crime. The family of the victim can decide to pardon someone convicted of a crime, Kumar said. In the case of honor killings, the accused is usually part of that family.
Progress on this issue will be slow, Kumar said. "It boils down to what's the definition of honor and changing that."
Nasrullah said the most important conclusion of his study is that more research needs to be done on honor killings to reveal more about the causes and scope of the problem. His hope, expressed in the published study is that "clear knowledge about the extent and the brutal consequences of [honor killings] may serve to alter traditional practices."