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Children's Screen Time: Symptom or Cause of Neurodevelopmental Disorders Like ADHD and Autism?


Parents of children with neurodevelopmental disorders (NDD) are often criticized for allowing their children too much screen time to reduce parenting difficulties, which can deprive children of opportunities to acquire language and social skills. This is the first study to show that genetic risks for NDD can affect screen time in children. Therefore, caregivers of children with the disorders should be supported and provided with alternative behavioral management strategies.


Neurodevelopment (ND) refers to the process by which the nervous system, including the brain, spinal cord, and peripheral nerves, develops and organizes itself from conception to maturity.


This process involves a series of complex steps that allow for the formation of neural structures and efficient communication between nerve cells, or neurons.


Neurodevelopment is fundamental to an individual’s physical, cognitive, emotional, and social growth. The ND events that occur in the Prenatal period are Neural Proliferation, which occurs after conception, neural stem cells multiply rapidly, forming a large number of nerve cells.

Representation of the main events of neurodevelopment at the cellular level. Source: Michael Aschner, DOI: 10.14573/altex.1604201. License CC BY 4.0


In the differentiation phase, nerve cells specialize into different types of neurons and glial cells (support cells). In the neural migration phase, newly formed neural cells migrate to different regions of the brain, where they position themselves to form brain structures.


Finally, the organization phase, where neurons begin to form connections between each other, creating synapses. This is the beginning of the neural network that will allow communication between the different parts of the brain and the body.


In the postnatal period (childhood and adolescence), the events of ND are synaptogenesis, even after birth, the brain continues to form new synapses at a very high rate. This is crucial for learning and the development of motor, linguistic and cognitive skills.


Over time, the brain eliminates synapses that are not used frequently, a process known as synaptic pruning. This helps make neural connections more efficient. This event is called synaptic pruning.


The final stage of development and maturation is myelination. Myelin, a substance that coats the axons of neurons, forms during childhood and adolescence. This coating is essential for the rapid and efficient transmission of nerve impulses.

Magnetic resonance imaging (MRI) images showing brain development in humans. Source: New Oxford Neurodevelopment Consortium


During adolescence, the brain continues to develop, especially in the prefrontal cortex, which is associated with planning, decision-making and impulse control. This development continues into early adulthood.


Neurodevelopment is influenced by genetic and environmental factors, such as nutrition, sensory input and social experiences.


Adequate interaction between these factors is essential for healthy development, while disruptions can lead to disorders such as autism and ADHD. During adolescence, the brain, especially the prefrontal cortex, continues to mature, which is vital for impulse control and decision-making.


Neurodevelopment therefore shapes an individual’s ability to learn, adapt and interact with the world throughout life.


Recently, the impact of screen time in childhood on the risk of developing neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) has generated much debate.


Some studies suggest that reducing screen time may protect against these disorders, while others find no direct association. These differences in results make it difficult to say with certainty whether there is a causal relationship between screen time and neurodevelopmental disorders.

To explore this issue further, a recent study published by researchers at Nagoya University Graduate School of Medicine in Japan investigated the link between genetic risks for neurodevelopmental disorders and screen time in children.


Using data from a long-term cohort study in Hamamatsu, Japan, researchers followed children from 24 to 40 months of age, monitoring their parent-reported screen time.


The assessment included interviews based on a standardized questionnaire, while genetic risks were calculated based on polygenic risk scores for ASD and ADHD. The results showed that children showed different trajectories of screen time over time. Some maintained low screen time, while others experienced either an increase or decrease in screen time.


The study found that genetic risk for ASD was associated with longer durations of screen time, suggesting that children with a higher genetic risk for ASD may be more attracted to screen stimuli.


On the other hand, genetic risk for ADHD was associated with increases in screen time, which may be related to these children's tendency to engage more in activities such as gaming.

The study also found evidence that having siblings may act as a protective factor against increased screen time, possibly due to increased engagement in outdoor play and development of social skills.


This suggests that the family environment may significantly influence screen-related behavior. Despite its groundbreaking findings, the study acknowledged some limitations. Screen time was self-reported by parents, which may introduce underestimation bias.


Furthermore, the type of content consumed during screen time was not differentiated, which may have different implications for child development. Finally, the study did not include formal diagnoses of ASD and ADHD, which limits the generalizability of its findings.


These findings highlight the complexity of the relationship between screen time and the development of neurodevelopmental disorders, pointing to the need for support for caregivers of children with elevated genetic risks and for more research to better understand these dynamics.



READ MORE:


The association between screen time and genetic risks for neurodevelopmental disorders in children

Nagahide Takahash, Kenji J. Tsuchiya, Akemi Okumura, Taeko Harada, Toshiki Iwabuchi, Md Shafiur Rahman, Hitoshi Kuwabara, Yoko Nomura, and Tomoko Nishimura 

Psychiatry Research, Volume 327, September 2023, 115395


Abstract:


Whether longer screen time in infancy increases risk of neurodevelopmental disorders (NDDs) such as autism spectrum disorder (ASD) and ADHD has long been debated, but no causal relationship between the two remains has been established. Using ongoing longitudinal cohort data, we found that in children 24 to 40 months of age, the genetic risk of ASD was associated with longer screen time and that of ADHD with an increase in screen time over time. These data suggest that prolonged screen time may not be a cause of the genetic risk for NDD, but an early sign of NDDs.

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