The impact of trauma on brain functioning and behaviour has been a growing area of study over the past few decades. While the medical model of mental illness focuses on symptoms and diagnostic criteria to define abnormal psychologies, trauma-informed theories look to a person’s life experiences to understand the context in which behaviours occur.

Adverse Childhood Experiences (ACE)

The landmark research of Vincent Felitti and Robert Anda (Felitti et al., 1998) examined the relationship of childhood abuse and household dysfunction to many of the leading causes of death in adults. Their findings revealed strong connections between childhood trauma (adverse childhood experiences or ACEs) and health risk behaviours, such as smoking and overeating, and physical illness and disease later in life, most likely due to neurobiological changes caused by chronically activated stress response systems. For a primer on ACEs see ACES Primer HD.

ACEs have been related to many criminogenic risks. In fact, research indicates that rates of both criminal justice involvement and victimisation are generally higher among homeless participants who had experienced any type of ACE (Edalati et al., 2017). While it is true that toxic stress may impact healthy development at any stage in our lives, we know that the brain has a few critical periods for growth and development, including neural pruning, that are specific to childhood. When a child’s brain is growing and developing, it is vulnerable to toxic stress, which has the potential to affect the very architecture of the brain itself, as well as the neurochemicals that travel between the various brain structures. For more on the impacts of toxic stress see Toxic Stress.

When a brain is exposed to extreme adversity or toxic stress, the amygdala gets inflamed and becomes enlarged over time. The hippocampus (responsible for visual spatial processing and memory consolidation) can lose volume and shrink. The neurochemistry that travels between these brain structures and the prefrontal cortex can also become impaired/weakened with trauma . In the end, the individual experiences poor impulse control, challenges with deciphering when real danger is truly present, and a quickly activated fight/flight stress response system. For more on the crucial connection between the amygdala and prefrontal cortex see The Raising of America | Documentary on the science of early childhood, working parents and public policy.

This neurobiology has an adaptive function: our neurobiological stress response incites our sympathetic nervous system to respond to our environment when there is imminent danger and engage in a way that helps us survive. For example, in 2019, a Vancouver Island mother intervened when a cougar attacked her seven-year-old son. When the sympathetic nervous system is activated, the stress hormones epinephrine and cortisol are released. Blood pressure and the heart rate increase, which enabled this mother’s heart to function at optimal efficiency while moving oxygen and blood to her muscles for increased strength, dilating her pupils to enhance her distance vision (she was able to see her son in the distance at the back of their yard), dilating her bronchi (allowing more air into her lungs), increasing blood flow to her skeletal muscles (allowing this mom to temporarily have “superhuman” strength) and sending blood sugars surging through her system (giving this mom extra energy and stamina). This sympathetic nervous system response is a highly important survival mechanism built into our brain and body that allows us to, for example, challenge and defend against a cougar attack on our child. For more on this story see ‘Hero’ mom punches mountain lion to save her son, 5.

A mechanism that is highly valuable in an emergency like this is not as useful in day-to-day life, however. When the sympathetic nervous system is chronically triggered, especially during early brain development, the threshold for flight-or-fight can be lowered, triggering behaviour that is impulsive, risky, combative, and sometimes illegal, in contexts where urgent action is not justified. For example, a young person who grew up in a home witnessing domestic violence and experiencing physical abuse may have a hyper-aroused sympathetic nervous system that incites them to defend themselves with aggression with little pre-contemplation or control before acting. A child who did not have their physical needs met as a child may not think twice before stealing food or other necessities for daily survival. This demonstrates the need for trauma-informed approaches across all systems of care to possibly prevent criminal behaviour in youth as well as develop a rehabilitative approach for those who have broken the law.

Trauma-Informed Models of Addiction

The trauma-informed model of addiction acknowledges a physiological, brain-based vulnerability to addiction that is influenced by genetics but also heavily impacted by supports and positive or negative experiences/influences in one’s life. The neurobiological impact of trauma paired with the psychopharmacological effects of substance use can have a combined effect on impulsivity, anger, and other behaviours and emotional states associated with crime.

The self-medication model hypothesises that substance use can help people cope with the experiences of trauma (Hawn et al., 2020). Post-traumatic stress disorder (PTSD) is caused by traumatic life events, resulting in persistent re-experiencing of the event; avoidance of feelings, thoughts, conversations or places associated with the trauma; adverse alterations in cognition and mood; and hyper-arousal (American Psychiatric Association, 2013). PTSD is associated with substance use, with PTSD often predating alcohol misuse and alcohol use to cope with negative emotions (Hawn et al., 2020; McCauley et al., 2012).

A trauma-informed approach considers early attachment relationships as a primary survival need in human beings. Humans have longer attachment relationships than any other animal, and attachment is not a negotiable need. Gabor Maté (2008) identifies authenticity as another legitimate survival need. In younger years, attachment needs take priority over authenticity. If authenticity challenges our attachment needs in early development, we suppress our authenticity to stay attached. Early childhood abuse and trauma, especially from caregivers, causes children to suppress their authenticity in order to prioritise survival/attachment. This disconnect can create an environment where toxic stress has the potential to impact one’s brain development, neurochemistry, and behaviours. Endorphins, which are naturally produced by the brain when one is calm and happy, facilitate attachment. Drugs classified as opiates mimic this pleasurable feeling in the brain—some opiate users describe a sense of euphoria, affection, and connection, creating an artificial sense of attachment. When an individual experiences stress or trauma, the natural endorphin receptors do not develop normally, potentially allowing for a vulnerability to opiate addiction.

Research has demonstrated the connection between exposure to traumatic events, impaired neurodevelopmental and immune systems and subsequent health risk behaviours resulting in serious physical or behavioural health issues (Felitti et al., 1998; Anda et al., 2008; Shonkoff et al., 2012). Unaddressed trauma significantly increases the risk of mental and substance use disorders and chronic physical diseases (Dube et al., 2003).