What is Trauma?

The U.S. Substance Abuse and Mental Health Services Administration (SAMHSA) explains that “Individual trauma results from an event, series of events, or set of circumstances that is experienced by an individual as physically or emotionally harmful or life threatening and that has lasting adverse effects on the individual’s functioning and mental, physical, social, emotional, or spiritual well-being.”

Over the last century, there has been considerable debate in the field of psychology about what qualifies as psychological trauma and what combination of symptoms should be considered sufficient to show post-traumatic stress disorder (PTSD). But while several definitions of trauma exist, most emphasize that there is a precipitating event that causes traumatic stress.

Symptoms of trauma

  • Memory loss or confusion about the event;

  • Alternating between feeling emotionally numb and experiencing intense and intrusive emotions;

  • Re-experiencing or re-imagining the traumatic experience;

  • Avoidance of reminders of the traumatic experience or what was lost in the experience;

  • Hypervigilance or a constant state of arousal;

  • Aggression; and

  • Disruption of identity

From the National Institute for the Clinical Application of Behavioral Medicine, NICABM.

Trauma and the Brain

Dr. Vessel can der Kolk on Three Ways Trauma can Change the Brain

The Three E's of trauma

SAMHSA’s definition of trauma is broken up into what we sometimes refer to as the Three E’s of Trauma: Event, Experience, and Effect.


An event, series of events, or set of circumstances


Experienced as physically or emotionally harmful or life threatening


With lasting adverse effects on functioning and well-being


The event and circumstances may include the actual or extreme threat of physical or psychological harm, like a natural disaster, violence, or a serious accident. But it doesn’t always have to be one specific, life-altering event that we can point to a day and time for. It can also be severe, life-threatening neglect for a child that imperils healthy development. And it can be racial, historical, or intergenerational trauma that is passed down through a family or community. Events and circumstances may occur as a single occurrence or repeatedly over time.


The way a person experiences the event or series of events determines whether it is a traumatic event. A particular event may be experienced as traumatic for one individual and not for another. How the person labels, assigns meaning to, and is disrupted physically and psychologically by an event will contribute to whether or not it is experienced as traumatic.

An important component of a traumatic experience is the feeling that a person has lost agency or control over their circumstances or that help was not available when it was needed or was denied by someone they should have been able to rely on. The event is experienced as dominating their ability to respond to the situation they were in. These events set up a power differential where something-- whether it’s another person, an event, or a force of nature-- has power over another.

The person’s experience is then shaped by this powerlessness and questioning of “why did this happen to me?” Feelings of humiliation, guilt, shame, betrayal, or silencing may become part of the experience. How the event is experienced may be linked to a range of factors including the person’s cultural beliefs, the availability of social support, and to the developmental stage of the person.

A particular event may be experienced as traumatic for one individual and not for another.


The long-lasting adverse effects of the event are what determine whether a person is experiencing trauma. These adverse effects may occur immediately or have a delayed onset.

The duration of the effects can be short to long term and can include a person’s inability to cope with the normal stresses and strains of daily living; to trust and benefit from relationships; to manage cognitive processes, such as memory, attention, thinking; to regulate behavior or control the expression of emotions. In some situations, the individual who has experienced the event may not recognize the connection between the traumatic events, their experience, and the effects they are suffering from.

In addition to the more visible effects of trauma, there may also be an altering of the person’s neurobiological make-up. In other words, trauma literally changes the physical brain. Advances in neuroscience and an increased understanding of the interaction of neurobiological and environmental factors have documented the effects of such threatening events.

Top Resources on Trauma

Trauma, American Psychological Association

Understanding the Impact of Trauma, U.S. Substance Abuse and Mental Health Services Administration