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Rape Victims Experience Involuntary Paralysis During Assault, Study Finds

It's not as simple as "just fighting back."

There is an ingrained belief that physical struggle is a primal and "normal" response to rape. That under attack, your survival instincts kick your mind and body into action. By this logic, women can only be raped when they are physically overpowered.

But the reality is that the majority of rape victims may experience involuntary paralysis that "blocks" active resistance, a new study has found. The term for this paralysis is "tonic immobility," and it could have real-world implications for how rape is treated in court and in hospitals.


"The courts may be inclined to dismiss the notion of rape [if] the victim didn't appear to resist," Dr. Anna Möller, the study's lead author, explains. "Instead, what might be interpreted as passive consent is very likely to represent normal and expected biological reactions to an overwhelming threat."

Read More: When Does Drunk Sex Become Rape?

Tonic immobility, described in the study as "an involuntary, temporary state of motor inhibition in response to situations involving intense fear," is already well-documented in animals (hence, "Deer in the headlights"). But far less is known about how it works in humans. Beyond the "freezing" effect, the study also notes a strong link between tonic immobility and subsequent PTSD and severe depression after rape.

To gather their findings, Möller and her colleagues from Sweden's Karolinska Institute assessed tonic immobility at the time of assault in 298 women. Among the women, 70 percent reported "significant" tonic immobility, and 48 percent reported "extreme" tonic immobility during the assault.

Of the 189 women who completed a six-month assessment, 38.1 percent had developed PTSD and 22.2 percent had developed severe depression. Research into tonic immobility among rape victims isn't new, but these findings show it to be "more common than earlier described," Möller told Broadly. She said that the results, published in the journal Acta Obstetricia et Gynecologica Scandanavia, could help inform the education of medical and law students.

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As the study points out, sexual assault is one of the most traumatic experiences a person can experience. However, "The legal system seeks visible signs of resistance because when it is absent, it is more difficult to prove a sexual assault."

For this reason—and for the ongoing mental health of the victim—tonic immobility "should be routinely assessed in all sexual assault victims," Möller said.