Biological mechanism HPA Axis that shows toxic stress can affect childs L-T health and psychological development

hpa axis

What is Hypothalamic Pituitary Axis HPA- Axis?

Our central response system

HPA Axis does:

• when something stressful happens to us, our initial response is mediated by the sympathetic nervous system

• this response occurs almost immediately and results in the secretion of epinephrine (adrenaline in the body that helps body act fast) and norepinephrine (non adrenaline - keeps brain ready and alert)

• BOTH hormones create changes you feel when scared or stressed, like faster heartbeat and sweating

HPA Axis process 1-7 steps

1. body experiences stress

2. hypothalamus is signalled and releases corticotrophin releasing hormone (CRH)

3. CRH signals to pituitary gland

4. pituitary gland releases Adrenocorticotropic hormone (ACTH) into the bloodstream

5. ACTH travels down to adrenal glands

6. adrenal glands releases cortisol from the cortex

7. release of cortisol helps the body’s functions to respond to stress

What is HPA dysregulation

• when a young child is exposed to toxic stress (e.g neglect), the HPA axis can become overactive or under-responsive, which is called HPA-axis dysregulation.

• it causes prolonged increases of cortisol in the body, influencing development due to the chronically elevated cortisol, inappropriate stress response and circadian rhythm of cortisol is out of sync

Importance and (Long-term) Outcomes of HPA Axis

• importance: too much cortisol can disrupt brain development in the hippocampus (memory), PFC (decision-making) and amygdala (emotions)

• outcome: emotional dysregulation (e.g high anxiety), poor concentration and memory and increased depression risk

• LT: problems with ER, anxiety/depression, learning, memory, immune functions and increases risk of mood disorders, weight gain and diabetes

what happens under toxic stress (0-2)

• when a child experiences frequent/prolonged stress, the HPA axis is constantly activated

  • leads to chronically high cortisol levels

• overtime the brain adapts poorly, becoming oversensitive and under-responsive

Long term impacts of toxic stress

• shrinking of stress-sensitive brain areas (e.g hippocampus and PFC)

• problems with memory, learning and ER

• greater risk of anxiety, depression and impulsive behaviour

Psychosocial stress and adversity: effects from perinatal period to adulthood ( Barreo-Castillero 2019)

• explains that early-life adversity alters the functioning of the HPA axis, leading to L-T dysregulation of the stress response system.

  • this disruption contributes to the both mental health problems and physically disease risk later in life

• exposure to toxic stress can overactive the HPA axis, leading to chronically elevated cortisol levels. overtime this disrupts the brains dev. particularly in the stress-sensitive regions like the amygdala and PFC, affecting emotional regulation and increasing the risk for anxiety, attention issues and mood disorders

Genes, environments and time. The biology of adversity and resilience (Boyce et al)

• HPA controls stress response

• children exposed to chronic stress without protective caregiving

• HPA axis can become chronically over activated, leading to excessive cortisol production

• Boyce 2021 describes how persistent HPA axis activation during early life disrupts the dev of key brain areas like the PFC and Amygdala, which are responsible for emotional regulation, executive function and social behaviour.

  over time the dysregulation can contribute to anxiety, impulsivity and difficulty managing stress in later childhood and adolescence.

Early adversity and critical periods: neuro-developmental consequences of violating the expectable environment (Nelson and Gabard 2020)

• authors discuss how early-life adversity, such as chronic stress, can disrupt the development of the HPA axis and the body’s central stress response system.

• that explains that during critical periods of brain development, the absence of expected environmental inputs (e.g responsive caregiving), can lead to maladaptive stress responses.

• This dysregulation of the HPA axis can result in heightened stress sensitivity and has been linked to long-term impacts on ER and MH

HPA-axis toxic stress impact on healthy dev

Exposure to toxic stress in the first 0–2 years can dysregulate the child’s HPA axis, leading to abnormal cortisol levels and impaired stress response. This disruption affects brain development, emotional regulation, and increases vulnerability to anxiety and behavioural problems. Early stress can thus have lasting effects on the child’s physical and mental health.

The neurobiology of stress and development, Gunnar and Quevedo (2007)

• found that children exposed to early adversity (e.g maltreatment) often showed altered cortisol patterns - either chronically elevated or blunt responses - which are linked to emotional reactivity, attention problems and poor social functioning later in life

Attachment theory HPA AXIS

Toxic stress and poor caregiving can cause insecure attachment, disrupting the HPA axis and leading to abnormal cortisol levels. This impacts brain development and increases risk for emotional and behavioral problems.

self regulation theory

Toxic stress can overwhelm a child’s ability to self-regulate by dysregulating the HPA axis and causing excessive cortisol release. According to Self-Regulation Theory, this makes it harder for the child to control emotions and behaviour. Without strong self-regulation, toxic stress negatively impacts cognitive, emotional, and social development.

toxic stress within conception-2y

• critical window doe emotional, physical and neurological development

• permanently alters and disrupts child’s developmental trajectory through biological and psychological pathways, leading to an increased risk in health conditions