Can Childhood Trauma & Chronic Stress Boost Dyslexia Risk?

When discussing childhood trauma, it's worth differentiating between adverse childhood events and early life stress. 

Adverse Events 

The National Child Traumatic Stress Network (NCTSN) defines a traumatic event as one that is “frightening, dangerous, or violent” and that threatens a child’s “life or bodily integrity” (NCTSN, n.d.). Witnessing a tragedy, having a serious illness, going through a family separation, and experiencing violence are all considered traumatic.

Children respond differently to such events. Their own personal traits have something to do with their ability to bounce back. Their resilience is also influenced by factors like cultural backgrounds and family resources.  

Stress 

Early life stress is a broader category of negative happenings that includes exposure to “nutritional restriction, abuse, neglect, and limited family resources” (Smith & Pollak, 2020).  Some experts also include exposure to environmental toxins, as well as to cultural stressors such as racism and discrimination. Exposures like these may be one-time events or lasting experiences. It’s important to note that an adverse event doesn’t have to be life-threatening to have profound effects on a child’s development. 

Under short-term stress, the body activates learning and memory centers in the brain, prompting sharper attention and enhancing the brain’s neuroplasticity, which is its ability to reprogram itself to adapt to new information (Kershner, 2020). But when stress goes on too long, or when stress is more than a child is personally equipped to tolerate, the brain diverts some of its resources away from cognitive processes to manage the flood of stress chemicals. The brain is forced to adapt.

These adaptations generally take one of two forms: a vigilant response or a habituation response.  

Vigilant Response

The brain and body adjust to severe stress by enabling a child to cope with an up-regulated (hyper-activated) central autonomic network (CAN).  Anxiety is higher, some brain structures may mature more quickly, and greater social skills are supported. Vigilant responses are common, but they can lead to a higher risk of mental and physical health issues both in childhood and later in life. Researchers in the field of evolutionary developmental biology think the vigilant response may be connected to ordinary, “garden-variety” reading difficulties unconnected to dyslexia. 

Habituation Response

In situations where stress is persistent but low-level, or where a child doesn’t have the personal resources to cope with it, the brain down-regulates the CAN, dampening or buffering the body’s response to stress. Habituation can look like dulled emotions, loss of motivation, delays in development, and difficulty with phonological skills, which are essential to reading. Research points to the habituation response as possibly being an underlying factor in the development of dyslexia. In other words, dyslexia may be the result of the brain’s complex adaptations to chronic stress (Kershner, 2020). 

The HPA Axis

The body’s stress response is managed by the CAN. That network has two primary pathways: the hypothalamic-pituitary-adrenal (HPA) axis, which prompts the release of the stress hormone cortisol, and the locus coeruleus-norepinephrine (LC/NE) system, which releases another stress-related hormone, norepinephrine. Both pathways support stress management and cognitive functions like learning to read.  

A balanced HPA axis helps the brain to repurpose existing neural circuits to make print-sound connections.  A balanced LC/NE system cues the brain to pay attention to letter-sound correspondence happening in the visual word formation area of the brain. When the two pathways of the CAN are balanced, learning to read is well-supported. 

But when chronic stress overloads a child’s brain, the CAN may become dysregulated (Kershner, 2024). In a study involving 81 children, 38 of whom had been diagnosed with dyslexia, researchers found that the HPA axis under-responded to psychosocial stress in children with dyslexia (Espin et al., 2019). That’s just one connection. More research is needed to clarify how a dysregulated HPA axis contributes to reading difficulties. 

Brain-Derived Growth Factor 

Brain-derived growth factor (BDNF) is lower in children with dyslexia compared to their neurotypical peers (Elhadiddy et al., 2023). BDNF is a protein known to regulate the growth and plasticity of neurons and synapses in parts of the brain involved in reading. It’s crucial for learning, memory, and visual motor integrating abilities—all of which are part of learning to read (Elhadiddy et al., 2023).

Researchers have linked BDNF to phonological working memory, which is the ability to pay attention to sounds, holding them in memory as we sound out words. We also use phonological working memory to pay attention to and remember information as we build meaning from words and phrases (Jasińska et al., 2016).

Studies show that chronic stress depletes BDNF; thus, researchers think low BDNF might be a reliable biomarker for dyslexia. More research needs to be done to understand the relationship between the two.  

Auditory Processing, Stress, and Dyslexia

Brain centers that process sound can be affected by early life stress and childhood trauma. In animal studies, researchers found that early life stress damaged the ability to hear short gaps in sound. Stress also impaired the ability to perceive and respond to rapidly changing sounds. Those skills are not only critical for perceiving speech (Ye et al., 2023), they are also really important in learning to read.

In fact, one of the key features of dyslexia is difficulty with phonological awareness, which involves the processing of speech sounds. Brain imaging studies have highlighted differences in brain areas that process letter and speech sounds in children with dyslexia (Di Pietro et al, 2023).

Researchers are still learning about the ways chronic stress affects the development of auditory processing.