The Impact of Trauma on Adult Sexual Assault Victims

PART II – The Neurobiological Impact of Trauma on the Brain

What is Trauma?

A traumatic event is one in which a person experiences something that is frightening, and overwhelming, and that entails a sense of loss of control.  In experiences of extreme threat, such as a rape or torture, it can feel like a threat to one’s ability to survive. Because events are viewed subjectively, this expansive trauma definition is more of a guideline. Everyone processes a traumatic event differently because we all endure them through the lens of earlier experiences in our lives.

In her paradigm-shifting book, Trauma and Recovery: The Aftermath of Violence--From Domestic Abuse to Political Terror, Judith Herman (1992) explains trauma in the following way:

Traumatic events overwhelm the ordinary systems of care that give people a sense of control, connection and meaning. Traumatic events are extraordinary, not because they occur rarely, but because they overwhelm the ordinary human adaptations to life … They confront human beings with the extremities of helplessness and terror and evoke the responses of catastrophe. (p. 65)

Traumatic events are not necessarily violent, though they violate a person’s sense of self and security. (Kammerer & Mazelis, 2006) Trauma is subjective; what is traumatic to one person might not be to another.

It is helpful for those in the criminal justice system to understand the defence circuitry and the neurobiology of trauma in order to understand the range of reactions victims might exhibit in threatening circumstances, such as being sexually violated or attacked. We have all heard victims say things like, “I just froze,” or “I was just lying there until it ended,” or “I didn’t know what to do, I didn’t feel like I could do anything.”

To understand the effects of trauma, it is necessary to grasp the fundamentals of the brain’s defence circuitry – how it protects itself – and the crucial role this circuitry plays in shaping victim responses to, and coping with, traumatic events, both at the time they occur, and in recalling and narrating them later. It is to these issues that the next sections now turn.

How the Brain’s Defence Circuitry Takes Control When Under Threat

In the face of fear and threat we react automatically. These reflexive reactions include the well-known fight, flight, or freeze responses. Most people are familiar with these responses. They register at two levels: conscious cognitive levels and unconscious physiological levels.

The field of neuroscience is moving towards understanding this two-system framework: one set of networks generates conscious feelings of fear and anxiety; a second set controls behavioural and physiological responses to threats. (Ledoux & Pine, 2016) The second operates largely unconsciously because the network is subcortical. (Ledoux & Pine, 2016) In other words, it is deep in the brain and disconnected from conscious awareness or language.

This distinction is important, since threats can present themselves below the threshold of consciousness and can thus trigger the defence circuitry without the person consciously recognizing feelings of fear. (Ledoux & Pine, 2016) Our nervous system is also continuously evaluating risk and safety in the environment, monitoring whether there is any danger or threat. 

When any of our five senses detects a serious threat, the brain’s defence circuitry is activated and a cascade of stress chemicals are released. When a threat to physical survival is imminent, the human brain, unless specifically trained to do otherwise, will switch to subcortical dominance and the defence responses of fight, flight, or freeze. The defence circuitry dominates brain functioning once activated.  (Mobbs et al., 2009)

How the Brain Responds to Traumatic Threat: Hormones and the HPA Axis

When the human brain senses a life-threatening event, some sensory information bypasses the cortex and goes directly to the defence circuitry. This includes the amygdala, part of the brain’s limbic system, which predicts dangerous stimuli and triggers the appropriate physiological responses to danger and threat. This is automatic and often largely unconscious. Under these circumstances, the amygdala can be informed about something fearful or threatening before the cortex even knows what’s going on. (Sapolsky, 2017) “The amygdala is not itself responsible for the experience of fear. Its job can be more appropriately viewed as detecting and responding to present or imminent threats.” (Ledoux & Pine, 2016, p. 1086)

The amygdala sends a message to another part of the brain called the hypothalamus which sends a message further down in the brain to the pituitary gland which then sends a message to the adrenal glands. This is called the Hypothalamic Pituitary Adrenal axis or the HPA axis. When the signal reaches the adrenal glands they release two types of hormones: adrenaline and cortisol. Adrenaline bolsters the ‘fight or flight’ response by constricting blood vessels and making the heart pump faster to rush blood to the body and brain. Cortisol is the other stress hormone which is released by the adrenal glands in times of stress – this suppresses the body from doing anything which isn’t necessary, such as digestion or higher cognitive processing.  This allows the brain and body to focus all of its’ resources into dealing with the threat at hand. The defence circuitry rapidly takes control of brain functioning, activating a multitude of brain body responses.

The activation of the defence circuitry is a key moment because—from then on— brain, body, attention, thinking, behavior, and memory processes are all dramatically altered in particular ways. (Hopper, 2018)  The first brain-based reflex response is to freeze. Freezing occurs when the amygdala detects a threat and signals the brainstem to inhibit movement. This can happen in less than a second; it is automatic and beyond conscious control. This response shifts a person into a state of vigilance for incoming attacks as the brain scans the environment to assess for danger while seeking out possibilities for escape.

To this extent, then, it is a misconception to think that people make a calculated or rational assessment when they are in a moment of threat or terror about what to do – should they “freeze,” or should they take “flight” or “fight”? The process is much faster and more automatic than that. It happens almost beneath or under our consciousness. When under threat, our capacity for rational and conscious calculation, which would occur under ordinary circumstances, is minimized or impaired.

Defence Circuitry Activation Impairs the Prefrontal Cortex Function

The prefrontal cortex is the center of executive functions in the brain. It is involved in managing complex processes like reason, logic, problem solving, planning and memory. Stress hormones flooding the brain can cause a rapid and dramatic loss of prefrontal cognitive abilities, limiting our ability to think, plan and reason in the face of threat. (Arnsten, 2009)

When an individual is under threat and their stress response is activated, and people temporarily lose executive functioning. This impairs not only planning and decision making but also affects the brain’s capacity to organize experience into logical sequences. What this means is that when people are in the midst of a serious threat or assault, brain regions are activated to help them survive the experience, increasing intense responses such as hyperarousal and altered attentional focus, while decreasing activity of brain structures involved in planning and strategizing. These neurological changes are why pilots, mountain climbers, paramedics and hospital emergency personnel practice emergency procedures over and over again, and they also carefully review checklists of what to do in a crisis.  It needs to become automatic for them how to handle a crisis situation.

These alterations in decision making and strategizing capacities help explain why asking a victim to account for the decisions she made around a traumatic sexual assault is not a reasonable request; it can be perceived and experienced as victim blaming. Most people who have experienced a traumatic, overwhelming event are not knowledgeable about the complex brain and body alterations that they experienced. They may not be able to explain even to themselves their own often confusing and counterintuitive behaviours at the time of the event or immediately afterwards.

For example, a woman reported to the police a sexual assault by a male roommate who had been out drinking and returned to their apartment intoxicated but forgot his door key, and pounded on the door, demanding to be let in. When she was later interviewed by a detective, this woman acknowledged unlocking the door to this roommate who she reported she feared, and who had previously assaulted her. During the preliminary hearing she was asked by defence counsel why, if she was so afraid of this person, she had answered the door to him, rather than simply calling 911. The woman answered that she didn't know why she had opened the door. This response was mocked and challenged by defence counsel and used to undermine her credibility.

The problem, of course, was that the victim would not be able to explain that her brain was flooded with stress hormones and she was unable to effectively choose the best course of action.  If the victim had been interviewed by a trauma-informed detective she may have been asked questions that would have made her neurobiological alterations explicit and as a result it would have helped explain this counterintuitive response. 

To ask sexual assault victims to account and explain their behaviors can result in undermining their credibility because they may try to offer explanations for their behavior that when challenged by defence, can expose feelings of shame and vulnerability, exacerbated in a victim blaming social context. Or they may make what appear to be inconsistent statements about what they think they were doing. These kinds of evidentiary difficulties can be avoided by trauma-informed police interviewing and prosecutions.

Altered Brain Functioning and the Shift to Reflexes and Habits

Following the immediate and initial brain based freeze response, the person must quickly assess other ways to respond to the threat. Again, this assessment is not a cool, collected rational assessment such as one would make when carefully weighing all the relevant factors in a normal life choice or set of circumstances. Instead, what happens is a split-second reaction following quickly on the heels of the freeze; the person selects the response from among the range of other typical, habit-based responses to extreme circumstances.

Why Sexual Assault Victims Rarely take Flight or Fight

These habit-based reflex reactions, including “flight” or “fight,” are the ones most sexual assault victims are least likely to have. Most women are not trained to effectively fight. Most sexual violence prevention information is cognitively based and fails to offer repetitive practice on how to physically defend themselves. Without this training, highly stressed brains will default to habitual behavior. Police forces and the military know the importance of sustained, repetitive training to prevent police officers and soldiers from freezing in the face of threat and to promote the ability to take carefully planned steps to respond effectively.

An additional barrier to effective, strategic resistance or defence for most women is the fact that the offenders are often men they know (Conroy and Cotter, 2017), persons who are supposed to be trusted. As a result, the experience is not only alarming and threatening, it is also simultaneously profoundly confusing and destabilizing. In these circumstances, women often report a diverse range of intense emotional and psychological responses, particularly in situations where they are sexually assaulted by men known to them.

Understanding these complex yet common psychological and neurologically based responses to traumatic and threatening experiences such as sexual assault helps to explain why some sexual assault victims don’t exhibit “fighting back,” “yelling,” “escaping,” or taking some other kind of expected action for which they are later judged or blamed.

Extreme Survival Responses: How Women Cope When There’s No (Perceived) Escape

What happens to a sexual assault victim when her passive habitual response of making an excuse, or attempting to appease doesn't work? In these circumstances, she is not consenting to the escalating sexual intrusiveness and she is unable to offer resistance because she is afraid and overwhelmed. These moments of sustained stress reactions have flooded her brain further with stress hormones and her functional prefrontal cortex is impaired so she is unable to strategize or plan an escape. When the escape seems impossible and the outcome of an assault unavoidable, then extreme survival reflexes will take over (Hopper, 2017)

These extreme responses include dissociation, tonic immobility (temporary paralysis) and collapsed immobility (e.g., fainting). These common survival responses to traumatic threat, which are triggered after the initial freeze, are explored below.


Dissociation describes the process of the brain protecting itself from overwhelming stimulus by splitting some aspect of the experience away from consciousness. This may include memory loss of certain time periods, events, people and personal physical responses (both physical and emotional). Dissociated people report a sense of being detached from themselves and their emotions. They often have the perception of things as unreal and report being unable to make sense of what is going on. Dissociation can be automatic for people who were traumatized earlier in life. Victims describe their experience as feeling like being on autopilot. Others report trance states, feeling in a fog or in a dream, and that they don’t feel their bodies.

Tonic Immobility

A person in a state of tonic immobility is in a state of involuntary paralysis and is unable to move or speak. Women describe feeling cold, and as having rigid muscles. Despite being paralyzed, the individual is fully aware of what is happening to her. Humans cannot control this defense mechanism. A recent Scandinavian study reported the sexual assault victims who experienced extreme tonic immobility were twice as likely to suffer PTSD and three times more likely to suffer severe depression flowing the assault. (Moller, Sondergaard & Helstrom, 2017) This response often leaves victims expressing distress that they were not able to move or to call out for help. Also, some victims can quickly go into and out of this state, paralyzed one moment and able to move the next. (Kozlowska et al., 2015)

Collapsed Immobility

A person in a state of collapsed immobility experiences a sudden and drastic drop in heart rate and blood pressure to the point that she may faint or pass out. She often loses muscle tone and may describe feeling limp.

In conclusion, dissociation, tonic immobility and collapsed immobility all can result from extreme fear and perception of defeat. Yet, in the context of a sexual assault it may appear to an uninformed observer that the victim who experienced tonic or collapsed immobility did not resist the assault at all. While it is true that the victim might not have resisted, it may well be because she was incapable of taking action due to the extreme constriction of thought, movement or action. Victims who respond with these extreme responses often feel shame and confusion and blame themselves for “failing” to resist.

Affirmative Consent Helps Address the Most Enduring Rape Myth

A woman does not need to fight back or resist in order to prove that she did not consent to unwanted sex. Canadian sexual assault law does not require proof of resistance to demonstrate a lack of consent. Nevertheless, in the popular imagination, women are often expected to resist in order to prove that they really were “real” victims of sexual assault. This is one of the enduring rape myths, that is, that a “true” victim of sexual assault will fight back or scream and yell, and if she didn’t she must have consented to the sex. This mistaken idea simply fails to understand typical responses to sexual threat, coercion, intrusion and/or fear.

Too often, sexual assault victims are asked, “Why didn’t you just fight back, or scream, or struggle, or run away?” Sexual assault victims who had a freeze response during an assault may also experience much higher levels of self-blame (i.e., "Why did I just lie there?”). These apparently passive responses of some victims of sexual assault may be perplexing to those who don’t understand the neurobiology of trauma or gender socialization. In fact, the brain’s defence circuitry often causes human beings to freeze initially in the face of danger. This is a normal response to threat. It’s the brain’s way of priming us for the next steps in reflexive action.

We have all been caught off guard by an unsettling and disturbing situation with someone. Now imagine that same experience with a person of greater power, a situation that also instills fear and danger and a sense of a looming threat combined with a sense of your own vulnerability and powerlessness.

People who are used to a sense of self-efficacy and personal power and agency find it difficult to imagine such circumstances. But women in intimate situations with men who they believe are trustworthy – exactly the situations where researchFootnote 6 has documented that most sexual assaults take place – may feel disempowered because they are destabilized by the unexpected betrayal, or cognitively constricted because of altered thinking capacity or physically restricted due to neurobiological responses. These complex reactions are often a hallmark of the context.

Conclusion: A Need for Specialized Education to Understand the Neurobiology of Trauma

The general public, the criminal justice system, even victims themselves often misunderstand neurobiological based responses to threat and to traumatic events. Victims cannot explain many of the responses they experienced, nor do they understand their own coping and reflexes. Sexual assault victims often find these reactions extremely frightening and confusing and they often blame themselves for these responses.

The self-blame and lack of information about these natural brain-based responses keeps many victims from coming forward to report their sexual assault experiences to police or to get support services. Many police also do not understand these responses and they may respond verbally or non-verbally (for example, through body language) in a manner that communicates disbelief, as a result undermining their investigation. In court, victims’ credibility is often undermined when lawyers inaccurately characterize, question, and challenge these seemingly counterintuitive behaviours. (Craig, 2018)

It is essential that members of the entire criminal justice system receive specialized education to understand the neurobiology of trauma, the defence circuitry, and the types of habits and reflex behaviours that victims of sexual assault often exhibit. Exposing triers of fact to this information will then allow them to determine the facts more impartially and make more informed decisions.