How childhood trauma impacts our brains, bodies – and even our genes

In 1966, Romanian dictator Nicolae Ceaușescu introduced extreme policies to increase the country’s birth rate. This led to the widespread abandonment of children, who ended up in orphanages in appalling conditions where they received no care, attention or love. Though tragic, this infamous “natural experiment” has allowed us to learn a great deal about the effects of early-life trauma on the brain.

Research into these children found that many of them had smaller brain volumes, which partially explained their poor cognitive performance. This atrophy was more severe in children who had spent longer in institutions.

 

Childhood is the most sensitive period for neurodevelopment, but sadly, it can be disrupted in many ways, from abuse or neglect to exposure to war and violence.

 

A question of stress

Understanding the neurobiological effects of childhood adversity can help us understand and treat its long-term psychological effects. Evidence suggests that these particularly affect the main stress regulation system, known as the hypothalamic-pituitary-adrenal axis. The activity of this system can be measured through hormones such as cortisol, collectively known as glucocorticoids.

 

In normal amounts, cortisol helps to mobilise the body to deal with threats or challenges. However, excessive amounts can be harmful – children exposed to war have elevated levels of both cortisol and immunoglobulin-A in their saliva, which also indicates high immune system activity.

 

Changes in the brain

The imprints of adversity in the brain can also be more localised. One of the areas most sensitive to the effects of stress is the hippocampus, a crucial structure in the formation of memories and spatial orientation, among other functions.

 

This sensitivity is due to its high concentration of glucocorticoid receptors, the “stress hormones” which are present in high levels in families exposed to war.

 

The largest and most recent study on the subject reported a 17% reduction in hippocampus size among children exposed to three or more traumatic events compared to those who had suffered none.

 

The two types of trauma

It is important to note that adversity varies not just in severity, but also in its type. Abuse or mistreatment leads to trauma by commission, while neglect or deprivation leads to trauma by omission.

 

A 2019 systematic research review found that adversity created by commission – such as physical or sexual abuse or exposure to gender-based violence – affects limbic and paralimbic structures, including the amygdala and insular cortex.

 

These areas are part of the brain’s “alert system”, and abuse causes them to be constantly overactive. This, in turn, causes extreme reactions to harmless stimuli, as seen in post-traumatic stress disorder.

 

In contrast, neglect tends to affect the prefrontal areas of the brain, which are responsible for more complex processes such as planning and reasoning. The latter was clearly observed in the aforementioned study of state-fostered children in Romania, where an absence of care resulted in brain atrophy and cognitive deficits.

 

Different types of adversity can also affect development in opposite ways: a 2018 study found that neglect slows maturation, while maltreatment accelerates it.

 

Childhood adversity’s genetic footprint

One of the most striking findings of this century is that circumstances and environment can change genetic mechanisms. This happens through a process called epigenetics, whereby certain genes are expressed to a greater or lesser extent depending on a person’s surroundings.

 

Abused children, for instance, have been found to show opposite to expected gene expression (high expression of genes that normally have low activity, and vice versa).

 

Childhood maltreatment also causes “genetic ageing”: a pattern of genetic expression that is more advanced than usual for a person’s age. This ageing is also associated with greater risk of depressive symptoms.

 

Another surprising finding is that some epigenetic changes can occur during embryonic development. A study on the tragic Dutch famine of 1944 found that people whose mothers had experienced starvation during early pregnancy showed alterations in the expression of genes related to metabolism.

 

This explains, in part, their elevated body mass indexes and blood triglycerides compared to siblings who had been luckier and not suffered from starvation while in the womb.

 

The neurobiology of resilience

It is important not to be defeatist: the brain is highly malleable, and many individuals can overcome early adversity. In psychology, this process is called resilience.

 

In one of the cohorts of adopted Romanian children, IQ deficits were observed to decrease over the years following foster care until they approached normative levels. In addition, those who were in these institutions for less than six months had, from the outset, normative values for all the variables studied.

 

Research into resilience is only just starting to reveal the neurobiological and psychosocial factors that mitigate the impact of severe and chronic stress. In some people, this can even enable what is known as post-traumatic growth.

 

Macià Buades Rotger, Profesor Lector (equivalente a Ayudante Doctor) en Psicología especializado en neurociencia cognitiva, afectiva, y social, Universitat de Barcelona

 

This article is republished from The Conversation under a Creative Commons license. Read the original article.