Poor Reading: A Deep Dive
The causes of APD
Understanding the causes of APD
The exact cause of APD often remains unclear in many cases, especially in children. However, research has identified several neurological, genetic, and developmental factors that can contribute to or increase the risk of APD:
Reasons why a child might have APD
The exact cause of auditory processing disorder is unclear, but research has identified several major factors:
Neurological factors
Any condition or injury that affects the brain regions involved in auditory processing can cause APD. For example, lesions or abnormalities in the brain’s auditory pathways (brainstem, auditory cortex, etc.) may lead to processing deficits. APD can also occur in the context of broader neurological disorders or after events like traumatic brain injury or stroke. Inefficient neural transmission — such as poor coordination between the left and right hemispheres or imprecise neural synchrony in auditory circuits — has been suggested as a possible cause of APD. These neurological “timing” issues mean the brain doesn’t synchronize well enough to interpret rapid sequences of sounds.
Genetic predisposition
There is evidence that genetics play a role in auditory processing abilities. APD may run in families, suggesting some individuals inherit a vulnerability in how their brain processes sound. However, no single “APD gene” is identified; it’s likely a complex interaction of genes affecting brain development. Researchers Bamiou et al. (2001) concluded that APD can be a feature of both neurological and developmental disorders, implying that genetic or developmental factors for those conditions (like language impairment or specific learning disabilities) might also lead to APD.
Developmental factors and early life experiences
Adverse events during prenatal or early childhood development can impact the auditory system. For instance, prematurity, low birth weight, or anoxic/hypoxic episodes (lack of oxygen) in utero or at birth are linked to higher risk of processing disorders. Certain infections (e.g. congenital cytomegalovirus) or neonatal conditions (e.g. severe jaundice leading to high bilirubin) can affect neurological development, including the auditory pathway.
Recurrent ear infections (otitis media)
Frequent middle ear infections in early childhood – especially if accompanied by fluid (effusion) – can cause intermittent hearing loss during a critical period for auditory development. This auditory deprivation in toddler years can disrupt the normal maturation of central auditory pathways. Studies have found chronic otitis media before age 2 is associated with auditory processing problems later on. Essentially, the brain missed consistent practice in interpreting sounds due to muffled hearing in infancy.
Prenatal exposure and toxins
Exposure to certain substances can harm auditory neural development. Maternal cigarette smoking during pregnancy has been linked to higher incidence of APD in children. Likewise, lead exposure in early childhood (a neurotoxin) has been found to cause central auditory processing deficits. These toxins likely disrupt the formation of neural connections necessary for efficient auditory processing.
The intersection of APD causes
In many children, APD is considered developmental, meaning it emerges as the auditory system develops, without a clear injury or event to point to. It’s not uncommon that the cause is unknown for a given child. In other cases, APD is acquired later in life (for example, after head trauma or in older adults due to neurodegenerative changes). It’s important to note that APD can co-occur with other developmental disorders like dyslexia or language impairments; in such instances, auditory processing deficits might share common causal factors with those conditions or exacerbate their symptoms. Ongoing research in neuroscience and genetics continues to explore why some brains develop auditory processing difficulties while others do not.
Next up: When listening affects writing
How auditory challenges can make it harder to get words onto the page
Auditory processing isn’t just about what your child hears—it also shapes how they express what they know. In our next post, we look at how APD overlaps with dysgraphia and why listening and writing skills often go hand in hand.