The potential effects of trauma and abuse on the developing brain and nervous system are powerful and incredibly complex.
Healthy brain development is highly contingent upon a number of highly interrelated neuroregulatory systems that are highly sensitive to the effects of environment and experience. In some instances, environmental factors influence the expression of genes responsible for proteins affecting neurotransmitter sensitivity and function. In other instances, circulating hormones affect development of critical brain regions associated with learning, memory, impulse control, mood and emotional self-regulation.
The neuroregulatory systems that help us to manage stress throughout life are extremely malleable during the prenatal period and early childhood. Toxic levels of stress during this period affect the development of these neuroregulatory systems in ways that cause those systems to become overly responsive to shut down in response to a wide range of stressors in later life.
Let’s look at how toxic stress affects the development of different systems and structures in the brain…
The hypothalamic-pituitary axis (HPA): The HPA plays a critical role in the body’s response to stress. The hypothalamus produces corticotropin-releasing hormone (CRH) which stimulates the pituitary gland to produce adrenocorticotropic hormone (ACTH). ACTH acts on the adrenal gland to increase levels of cortisol (see diagram at top of page). Cortisol is a steroid hormone produced in response to a wide variety of stressors. Cortisol mobilizes energy stores and suppresses immune response. Surgeons prefer to operate early in the morning when cortisol levels tend to be at their highest. Long-term elevation of cortisol levels in children (as seen in kids exposed to high levels of acute or chronic stress/abuse) can turn off the glucocorticoid receptor gene (involved with regulation of the long-term stress response of the brain to cortisol) and the myelin basic protein gene, producing the “insulation” of nerve cells that allows for efficient nerve signal transmission. Elevated cortisol levels also cause damage to the hippocampus (below).
The hippocampus: The hippocampus is a structure that plays a key role in learning by consolidating information from short-term to long-term memory. The hippocampus is capable of growing new neurons in adulthood. Damage to the hippocampus from elevated cortisol levels in childhood leads to impairments in learning and memory.
The locus coeruleus/noradrenergic brain systems: The locus coeruleus is a region located in the brainstem where the cell bodies of most noradrenergic neurons are located. This system is involved with regulating the overall level of arousal in the central nervous system. Exposure to stress/trauma early in life have been associated with lifelong increases in noradrenergic reactivity.
The noradrenergic system (along with the dopaminergic system) is the primary system associated with executive functioning. Tracts of neurons originating in the locus coeruleus project to the posterior attention center in the parietal cortex (responsible for scanning the environment for relevant stimuli) and the anterior fronto-striatal system, which is more involved with executive control and focusing attention. The posterior center is primarily under noradrenergic control, while the anterior center receives both dopaminergic and noradrenergic projections. Difficulties associated with weaknesses in executive functioning include poor impulse control, diminished capacity for emotional self-regulation, delaying gratification and problems with working memory. Editor’s note: This may help to explain the increased prevalence of ADHD among kids who have been traumatized or abused along with the observation they are frequently less responsive to medication than kids with ADHD lacking such exposure.
Dopaminergic systems: Numbing, decreased interest in pleasurable activities and difficulties with ability to maintain focus upon a task are associated with pathways mediated by dopamine. Dopamine pathways originating in the midbrain projecting to the medial prefrontal cortex may be especially vulnerable to the effects of acute and chronic stress. These pathways also play a role in selective information processing, working memory, and applying previously learned information to new experiences. Pathways from the medial prefrontal cortex to the amygdala are thought to play a role in mediating the response to fear.
Serotonergic/GABA systems: Alterations in these systems in response to stress/trauma contribute to difficultiess in social attachment and regulation of mood and affect following early stress.
Here’s a diagram from an article in Child and Adolescent Psychiatric Clinics of North America that shows the interrelationship of the different neural circuits involved in childhood PTSD…
Bottom line…The neuroendocrine changes that occur in response to trauma in children are widespread, long-lasting, and impact mood, learning, arousal, impulse control, memory, emotional self-regulation, and contribute greatly to future response to stress.
Updated March 4, 2016
