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Childhood Trauma and the Developing Brain

By Tim Hannan

A new study has identified the neurological basis for why some adolescents who have experienced childhood trauma are resilient while others are prone to mood disorders.

Psychologists have long recognised the challenges inherent in treating children who have experienced trauma during childhood, especially where this has been repeated in occurrence, extended in duration, or severe in impact. The effects of such early experience include a range of emotional, behavioural and cognitive symptoms, presumed to result at least in part to trauma-induced changes in the developing brain. A new study has identified specific brain mechanisms that are affected by early trauma and associated with successful adaptation and vulnerability to mood and anxiety problems.

The term “complex trauma” is commonly employed to refer to the experience of distressing adverse events, such as physical, sexual or psychological abuse, emotional neglect or abandonment, or exposure to violence at home or in the community. These events are often interpersonal in nature, may be frequent or continual, and can give rise to diverse consequences ranging from specifically trauma-related symptomatology (traumatic stress disorders) to behavioural disturbances (oppositional and antisocial behaviours), emotional problems (impulsivity, suicidality), educational difficulties, and broader interpersonal and personality problems.

It is well established that a key factor in child development is the quality of the relationship between the child and the primary caregiver in the first year of life. This is conceptualised as “attachment”, which refers to the pattern of interaction between the infant and primary caregiver.

Where a caregiver is attuned to the behaviour of the infant, and is able to identify and modulate the infant’s level of arousal and emotional states, the relationship is said to represent “secure attachment”. However, when infants experience inadequate or inconsistent responses from the caregiver, the initial reaction includes signs of elevated arousal, such as crying and screaming. If this proves ineffective, the child is likely to disengage from external stimuli.

This response, termed “dissociation” is thought to result from the parasympathetic nervous system initiating a survival response in order to combat the increased physiological arousal arising from the sympathetic nervous system. In the presence of repeated or prolonged adverse interactions, this dissociative response may become habitual.

While previous research has supported the assumption that the long-term effects of adverse early experiences in early childhood are due to changes in the developing brain, with the limbic region and cortical areas of the right hemisphere especially implicated, the neural mechanisms involved remain little understood.

In the study recently published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging, researchers from the University of Wisconsin examined associations between childhood adversity and mood in 132 participants followed from infancy to 18 years of age. Indicators of adversity included maternal depression, negative parenting, parental conflict, maternal role overload and financial stress in the family. At the final assessment, the 18-year-old participants underwent functional MRI analysis while completing an emotion-processing task using pictures that evoked positive, negative or neutral emotions. The MRI examined activation and functional connectivity in the prefrontal–amygdala and prefrontal–hippocampal pathways.

Consistent with previous research, adverse experiences during childhood were associated with both amygdala reactivity and prefrontal–hippocampus connectivity when participants viewed negative emotional images. This effect was not found when the adversity was experienced during the adolescent years, highlighting the importance of early childhood for the development of the neural mechanisms underlying coping with adversity.

However, examination of the responses of those with and without mood and anxiety symptoms produced a particularly interesting result. Early adversity was only associated with increased connectivity between prefrontal regions and the amygdala when negative stimuli were presented to adolescents who didn’t present with significant mood or anxiety symptoms.

This may indicate that children who successfully adapt to early adverse experiences have developed enhanced connections between the prefrontal and subcortical regions devoted to dealing with negative emotional stimuli. Conversely, reduced connectivity between these regions may be a marker of vulnerability for mood and anxiety disorders by the age of 18 years.

The study’s implication is that it may be possible to identify the neurobiological mechanisms that both facilitates the successful adaptation to adversity that some adolescents demonstrate and predicts the presence of mood and anxiety problems in others. The development and integrity of this system is presumed to be affected by the severity of the traumatic experiences, moderated by other individual, family and environmental factors.

These findings increase our understanding of the effects of trauma on the developing brain. It is hoped that such studies will enable the development of new interventions that, by being better informed by an understanding of neurobiology and sensitive to the developmental stage, may be more effective at ameliorating the effects of early trauma.

A/Prof Tim Hannan is Head of the School of Psychology at Charles Sturt University, and the Past President of the Australian Psychological Society.