(CNN) The majority of suicide bombers used by terror group Boko Haram to kill innocent victims are women and children, a US study reveals.
Researchers at the Combating Terrorism Center at West Point and Yale University analyzed the 434 suicide bombings carried out by Nigeria-based militants Boko Haram since 2011, and found that at least 244 of the 338 attacks in which the bomber's gender could be identified were carried out by women.
The ISIS-affiliated insurgent group has sent 80 women to their deaths in 2017 alone.
Boko Haram's use of women as bombers increased following the abduction of 276 female students aged between 16 and 18 from their school dormitories in April 2014. The Chibok Girls' abduction prompted the global "Bring Back Our Girls" campaign.
"Almost immediately after the Chibok kidnappings ... Boko Haram's use of women suicide bombers skyrocketed," says Jason Warner, assistant professor at the Combating Terrorism Center at West Point, the United States' elite military academy.
The report suggests "that Boko Haram started using women suicide bombers after it realized the potency that gender and youth offer in raising its global profile after the Chibok kidnappings," he says.
As well as regularly employing women to carry deadly explosives, Boko Haram is also "at the forefront of normalizing the use of children as suicide bombers," according to the report.
"Boko Haram has shattered demographic stereotypes as to what a suicide bomber looks like," says Warner. "It is the first terrorist group in history to use more women suicide bombers than men, and is at the vanguard of using children as suicide bombers."
Of the 134 suicide bombers whose age could be determined, 60% were teenagers or children. The youngest suicide bomber identified to date was just 7 years old.
Boko Haram has used four times as many young girls as it has young boys, according to the study.
Ellen Chapin, a Yale-based researcher who worked on the report, told CNN the militant group "deployed 42 teenage girls and 23 little girls (12 years old and under), compared to 11 teenage boys and five little boys."
The group's reign of terror has left an estimated 35,000 dead over the last six years; Warner says the "vast majority" of the group's victims are "innocent, everyday Nigerians, Cameroonians, Nigerians and Chadians, not government or military personnel."
"The loss of life caused by Boko Haram -- and the war against the group -- has been staggering," Warner says, adding that the conflict has forced more than two million Nigerians to flee their homes, with "profound humanitarian consequences."
The report's authors say there are several reasons why women and children are chosen as bombers, one being that they are far less likely to be searched.
They can hide explosives under their billowing clothing, or inside handbags, and in some cases have even strapped explosives on their backs with infant children.
There are also reports of men dressing as women to slip through security more easily.
The researchers also believe that women and children are more susceptible to Boko Haram's recruitment efforts than their male counterparts, through violence, brainwashing or false promises.
Women and female children, in particular, are seen as expendable by the male terrorist leadership -- their vulnerability a destructive, deadly curse.
One former insurgent told researchers that women "are cheap and they are angry for the most part," adding that "using women allows you to save your men."
Hilary Matfess, one of the lead authors of the report, told CNN the group's choice of suicide bombers "upends social norms about women and children, which make them effective beyond merely the lives that they claim when they are detonated."
The spreading of mistrust caused by the use of women and children in such deadly roles "undermines social cohesion and will make the process of post-conflict reconciliation and redevelopment all the more difficult," she says.
Researchers' fieldwork for the study was limited because northeastern Nigeria -- where Boko Haram is based -- is notoriously dangerous for locals and foreigners.
"Media reports often did not report full details of the bombings," says Warner. "Even getting approximate ages of bombers proved to be very difficult ... and media accounts often did not even report the gender of the bombers."
"In instances where age or gender was not reported, it might be reasonable to expect that the bomber was an adult man, and thus, age and gender were not newsworthy enough to report at all," he says.
Matfess spent much of her time in the field conducting face-to-face interviews with former Boko Haram insurgents, victims and family members affected by Boko Haram's reign of terror.
She said that as well as true suicide bombers, who are willing to die for a cause, Boko Haram also uses improvised explosives carried by unwilling victims and others coerced verbally, physically, materially or by violence. These are known as person-borne IEDs, or PBIEDs.
"Children and those forced into serving as bombers cannot be considered 'suicide bombers' and the counterterrorism measures against PBIED attacks can differ than the tactics deployed against an autonomous, dedicated suicide bomber," she says.
In Maiduguri, a town hit hard by Boko Haram's suicide bombings, Matfess says the government has begun a campaign to raise public awareness about women and child bombers, explaining how to identify potential attackers.
"The policy is well intentioned, [but] it risks stigmatizing the bombers, many -- though not all -- of whom have been coerced or forced into serving in this role," she said, adding that "the widespread suspicion of women and girls that these attacks have resulted in already puts women and girls at a disadvantage in the community."
Matfess said former Boko Haram members had told her that some women do join Boko Haram voluntarily, and some even volunteer to be suicide bombers.
She recalled a meeting with a group of female Boko Haram members who had been "rescued" by the Nigerian military and were being held in a rehabilitation camp, but who "were still loyal to the insurgency."
After talking to one of the group's younger recruits, a 14-year-old called Fatima, who had already been married twice, the girl asked to braid her hair.
"It was so clear to me then that this was just a young woman, with interests not very different from the [teenage] girls I grew up with, caught in the middle of tragic circumstances and a society marked by structural violence against women."