Researchers from the Karolinksa Institutet and the Stockholm South General Hospital in Sweden have investigated the theory that many rape victims are unable to fight off their attacker due to a physiological reaction in a harrowing situation.

With many victims forced to face questions over their apparent 'lack of resistance' during a rape, researchers in Scandinavia sought to analyse the response of women during sexual assaults.

According to their research, the vast majority find themselves unable to move which subsequently blocks their ability to fend off an attacker.

The response is known as 'tonic immobility' and has been described as "an involuntary, temporary state of motor inhibition in response to situations involving intense fear."

Using 298 women, who had visited the Emergency Clinic for Rape Victims in Stockholm within one month of a sexual assault, researchers established that 70 per cent reported significant tonic immobility during their assault while 48 per cent reported extreme tonic immobility.

In the six months following the attack, 189 of the women were assessed for the development of PTSD and depression. Findings indicated that 38 per cent had developed PTSD while 22 per cent had developed severe depression.

The risk of developing PTSD increased by 2.75 if the victim experienced tonic immobility while the risk of depression increased by 3.42.

The study comes as welcome news in both the medical and legal worlds as researchers seek to highlight the importance of the finding.

Speaking to Broadly, the study's lead author, Dr Anna Moller, said: "The courts may be inclined to dismiss the notion of rape [if] the victim didn't appear to resist."

"Instead, what might be interpreted as passive consent is very likely to represent normal and expected biological reactions to an overwhelming threat."

"This information is useful both in legal situations and in the psychoeducation of rape victims. Further, this knowledge can be applied in the education of medical students and law students," she added.

The findings have been published in Acta Obstetricia et Gynecologica Scandinavica.