In this final section of the paper I reflect on research into various environmental factors impacting neurological development, either suggesting a direct or indirect impact on the rise in Autistic diagnoses. I also invite the reader to weigh up how hereditary and environmental factors may be interacting to disproportionately affect disadvantaged socioeconomic groups.

As discussed in part 2 of this article, ASD is a neuro-developmental disorder which is aetiologically heterogeneous. In light of the most recent research, it is necessary to link this with unanswered questions raised by earlier research, in order to reconsider the impact of a range of factors which may previously have been considered innocuous. We now know that such environmental factors may be more seriously impacting our gut health than previously recognized and indirectly contributing to a rise in a number of health conditions, as well as a rise in the prevalence of ASD.

The importance of considering both Hereditary and Environmental factors:

Previous studies have shown that genetics play an important, but not exclusive role in the incidence of Autism. A large longitudinal Swedish study, established that 50% of children diagnosed with Autism were hereditary, leaving questions about the environmental factors that may be causing the other 50%. It is therefore a matter of social responsibility that we coordinate what is known about a range of negative environmental factors which may be interacting and contributing to the steady rise in the prevalence of ASD (Malone, 2025; Sandin, 2014; Sarris, 2025). 

The composition and function of the gut microbiota are in turn also profoundly influenced by genetic factors, (Qin et al., 2022). Specific gene variations can disrupt the balance of the gut microbiota. They can also be affected by environmental factors interacting with hereditary genetics to impact on gut health (Angrand, 2022; Sandin, 2014). Genetic background, prenatal stress, and environmental exposure to certain toxins collectively help shape the gut microbiota so the bi-directional relationship between all of these is important to our understanding. Susceptibility to negative environmental factors can be mitigated to a degree by a resilient gut microbiota. Since the immune system acts as a convergence point between ASD-related genetic and environmental risk factors (Angrand, 2022) this interaction between environmental influences on the body and factors affecting its inherent resilience to mitigate those influences, is recognized as increasingly important (Zhou et al., 2025).

Whilst so much fundamental research into the subject is ongoing, some links have already been well established, for example, between autism and parental age (Lyall et al., 2020). To a limited extent, we can conclude that this connection is associated with the rise in average age of when people start to have families. There are also known links with prematurity (Crump, 2021), and maternal infection (Al-Beltagi, et al., 2023) during pregnancy, so for example, numbers diagnosed with Autism may have been disproportionately impacted by the Covid Pandemic (Al-Beltagi, et al., 2022).

Recent studies of significance, however have focused on the significant impact of various environmental toxins in the pollutants around us (Angrand, 2022). The body’s ability to process such toxins may depend on both the gastrointestinal resilience and age of the unborn or new born child. Whilst the composition and function of the gut microbiota are profoundly influenced by genetic factors (Qin et al., 2022), research is now indicating that underlying gut microbial imbalance could make a child and the child’s off-spring more susceptible to such toxins, ((Skinner, et al. 2022; Wong et al., 2021).

Epigenetic factors

Epigenetics refers to the heritable changes in gene expression without changing the underlying DNA sequence. It addresses the way in which behaviours and environment can cause changes that affect the way genes work. Unlike genetic changes (mutations), epigenetic changes are reversible (Loke et al., 2015). These are changes that can take place in response to a person's experiences and environment over the course of a lifetime and can be passed down to future generations (Zieba 2025). Current research is exploring how such exact factors interact to impact on early neurological development. Results of some studies, appear to show that epigenetic changes can potentially play a significant role in the development of ASD (Eshraghi, 2018). 

Studies reveal that the negative effects of harmful toxins routinely used in our ecosystem, are often not detected until they become apparent in subsequent generations (Mulligan, 2025). Maternal exposure to pollutants, drugs, alcohol and poor diet can have a significant impact. Pesticides, heavy metals, and other environmental contaminants can enter the human body through the food chain, disrupt the balance of the gut microbiota. As a result they may induce inflammation, and lead to immune dysfunction contributing to long-lasting neural and cognitive impairments (Ali & AlHussaini, 2024; Rezazadegan, 2025).

Therefore, it is important to recognize that future generations can be more impacted than those directly exposed (Skinner, et al. 2022). The essential interplay between gut microbiota and epigenetic mechanisms is now considered to be a critical area of future research into understanding how rates of many neurodevelopmental disorders may be affected (Kim et al., 2024).

Immunity and susceptibility to vaccination:

The composition of the intestinal microbiota plays an important role in the development and regulation of immune responses. Crucially, these responses can in susceptible young infants influence responses to vaccination (Zimmermann, 2023). Studies have identified genetic variants that are associated with vaccine induced autoimmune activation. There is now an improved understanding of the relationship between the Immune System and the way in which the way it can be activated in the early stages of development by vaccination (Vadalà, 2017). Studies have shown that children with a family history of autoimmune disorders are significantly more likely to develop autism. It appears that this may be particularly important for those with compromised or immature immune systems, such as in certain newborn infants and especially premature infants due to the close connections between the Central Nervous System, the Immune System and the developing brain (Crawford, 2018).

Due to increased anecdotal reports of rapid onset Autism or Vaccine-associated regressive autism (VARA) at, or soon after vaccination, there is renewed concern that there may be a causative link, not previously studied, in a critical subset of children with additional genetic and environmental risk factors. VARA is defined as a rapid-onset loss of previously acquired milestones in central nervous system (CNS) development that are expected within the first years of life (Crawford, 2018). Certain more vulnerable infants may experience the cumulative effect of multiple vaccines over a short period of time contributing to functional impairment of the Central Nervous System (Crawford, 2018).

Recent research is re-examining the toxicity of low levels of Alluminium based Adjuvants (ABAs) for very young susceptible babies with gut microbial dysbiosis. Levels previously considered inconsequentially low compared to levels naturally ingested through drinking water, may have a greater impact than previously thought when delivered directly into the muscle through frequent vaccination. When injected intramuscularly, Aluminium oxyhydroxide is assimilated at nearly 100% efficacy over time, whereas when consumed orally, absorption is less than 1%. In addition, the adjuvant essentially remains immune cell-bound after injection and is not eliminated quickly through urine, but retained within the body. It is thought that this may therefore be a critical factor in understanding why they trigger an adverse response in certain children (Angrand et al., 2022; Crépeaux, G. 2018).

Further research is needed to consider questions about any ongoing epigenetic effects that levels of toxicity in vaccines may have had on subsequent generations. Underlying genetic and environmental risk factors may be crucial to our understanding of how the child responds to multiple vaccines administered over a concentrated period of time, in early infancy. Notably, this understanding is already giving rise to research into the development of potential therapies such as the use of probiotics and faecal transplants to improve the microbiota composition and vaccine efficacy (Zimmermann, 2023).

Micro-plastics

There is now rising concern about how the ubiquitous use of micro-plastics could be affecting brain development as a result of their impact on gut microbiota, (Zaraska, M., New Scientist, 7 May 2025). The ability of micro-plastics to promote microbial dysbiosis as well as gut inflammation and dysfunction suggests they are more harmful than previously thought. Their ability to permeate from the gut to other parts of the body have been shown to have adverse effects on the immune and nervous systems. This is therefore another environmental pollutant that may be another factor contributing to neurological disorders, (Sofield, S; Sun, J. (2024).  Surprisingly, it has been highlighted by researchers that commonly used teabags, even contain varying amounts of microplastics (Tooba, et al. 2023, Fard et al., 2025).

Gut microbiome and Electro-magnetic field hypersensitivity

Studies have shown a potential link between gut microbiome and electro-magnetic field hypersensitivity and certain neurobehavioral disorders (Luo, X et al., 2021). Long-term low-dose electromagnetic field (EMF) exposure can cause central nervous system dysfunction without effective prevention.

A significant number of concerns have been raised about adverse hypersensitivity reactions to non-ionizing electromagnetic fields, such as Wi-Fi and high frequency mobile telephone networks (i.e. 3G-4G).  With the prevalence of conditions such as colon cancer and gluten intolerance increasing, researchers are interested in exploring the connection between the microbial state of the gut, and the growth-altering effects that EMF has on intestinal bacteria, (Manzetti, 2022). These issues may in future be found to have implications for some neurodevelopmental disorders.

Retained Primitive Reflexes and maternal stress (RPR)

Primitive reflexes are there to assist in the birth process, feeding and survival movements necessary in the early days following delivery. Examples are the Moro, or startle reflex, and the spinal reflex which allows an infant to slide down the birth canal. This asymmetrical reflex allows the infant to participate in the birthing process during natural delivery. The major role of these reflexes therefore is to enable the infant to move and respond to its surroundings before maturation of the motor cortex. The infant needs to feed, move, obtain nourishment, receive protection, and orient to people and objects to stimulate its senses and muscles, to assist in early brain development. If such reflexes do not mature normally, it impacts on future areas of development involving  gross and fine motor skills. They typically disappear within the first few months of birth. 

Children with neurobehavioral disorders, frequently demonstrate Retained Primitive Reflexes (RPRs) that are thought to be related to maturational delay in the nervous system. They essentially result from environmental influences that are not genetically determined  and can reflect abnormal asymmetrical development and interaction between the hemispheres of the brain (Melillo et al., 2022).

There are a number of different reasons why primitive reflexes fail to integrate. Maternal stress during pregnancy, birth or early infancy is considered to be a key factor. One of the biggest factors that cause reflexes to be retained is a traumatic birthing process. This includes prolonged or premature birth, breach position, births involving forceps or suction, and Caesarean section births. which suggests the importance of  environmental factors affecting a mother’s well-being and stress levels. 

Screen Induced Pathological Vestibular reflex (SIPVR)

A recent study investigated the emergence of an acquired reflex and example of a possible epigenetic effect. Screen Induced Pathological Vestibular reflex (SIPVR) is induced by screen stimulation and addiction, making it an acquired pathological reflex, specific to environmental influences (Vezenkov & Manolova, 2025).

This reflex is an abnormal or dysfunctional response of the vestibular system, which is responsible for balance and spatial orientation causing vertigo, dizziness and balance problems. The vestibular system, located in the inner ear, plays a crucial role in maintaining balance and coordinating eye movements with head movements.

The severity of the reflex is clearly correlated with the severity of autistic traits in children with early screen addiction. They displayed intense levels of sensitivity to covering their eyes with hands (observed in 270 children, 95%), as well as hypersensitivity to loud noises.

Trauma impact on future generations:

Research has recognized how the effects of traumatic experience on the brain and body involve changes at nearly every level from brain structure, function and connectivity to endocrine and immune systems, from gene expression (including in the gut) to the development of personality (Laricchiuta, 2023). It is particularly relevant that early life stress has been linked to negative effects on a number of neural-developmental systems (Smith & Pollark, 2025).

Early infant experiences of adversity appear to increase the risk of both gut microbial dysbiosis and later adolescent mental health problems, as well as gastrointestinal symptoms associated with internalizing behaviors and anxiety, (Callaghan et al., 2020). Research suggests that extremely stressful events and trauma can also affect a person's epigenetics. Maternal stressors including nutritional deprivation, toxicant exposure, domestic abuse and violence are known to impact a developing fetus (Mulligan, 2025).

It has also important to consider that children with Autism are especially vulnerable to experiencing severe trauma adverse and have an increased risk of mental health issues (Kerns, 2024; Takeda et al., 2024). There are therefore important implications for understanding the potential relationship between neurological development and inherited trauma as the mechanisms that may mediate immunity-related neurodevelopmental alterations (Mulligan et al., 2025).

Conclusion:  Keeping an open mind

It is thought that epigenetic factors related to lifestyle changes over the past two decades, including the reduction of early motor activity and spatial exploration of children, have contributed, to the significant rise in the incidence of ASD. In addition, opportunities for children to engage with physical activities beyond the confines of their own homes can be more limited in economically disadvantaged households and increase their chances of becoming dependent on interaction with screens as the only form of diversion and stimulation. This may deprive them of any mitigating effect they might gain from opportunities to engage with more physical exercise which has been shown to improve gut microbiome (Varghese, 2024).

There are many reasons to believe that families under financial stress are more susceptible to trauma and ill health than those who are more economically stable. It is therefore important to recognize that a strong association has been made between Autism and Adverse Childhood Experiences (Kerns, 2017). In view of our understanding that stress can disrupt the gut microbiota which in turn can influence neurological development in young infants, these links are significant.

The research discussed in this review sheds light on the impact of diet including substance abuse, maternal stress, antibiotics, pollutants, micro-plastics, electro-magnetic fields and vaccine adjuvants, loss of early motor activity, early exposure and addiction to digital screens, and how they may all be interrelated. If they all have the potential to impact on the healthy functioning of the immune system then they all play a part in our understanding of how typical neurodevelopment may be affected.

Moreover, these studies also provide a starting point a deeper understanding about why certain children might be disproportionately affected, particularly those born into socioeconomically deprived sectors of society. It would benefit all scientific research for this debate to be encouraged and for all stakeholders to retain an open mind about what is driving the apparent rise in prevalence of ASD. It will encourage a closer questioning and scrutiny of the known facts, develop a more honest understanding, and lead to more effective appropriate support for those who need it.  

The relatively rapid way in which our society has learned about neuro-diversity in general, has overwhelmed an unprepared, poorly equipped education system that has been in deficit since the introduction of severe budget cuts in 2010 following the economic crisis of 2008 (Sibieta and Snape, 10 Dec., 2024). The inevitable backlog of unaddressed SEND needs has created an ever burgeoning pent up demand for more appropriate and consistent levels of support. As a result parental noise of discontent and stress among school staff, has correspondingly increased. Inevitably, unmet SEND needs, not only impact negatively on the children themselves and those supporting them, but leads to secondary behavioural responses which increase the likelihood of detrimental suspensions and exclusions from school.

When government services are aiming to reduce demand, the most immediate solution appears to be to make a case for reducing diagnosis (DfE, March, 2023; Moore, 2023). However, this approach may prove to be counter productive (SNJ, 2025). If diagnosis has increased because provision is inappropriate without it, reducing diagnosis is simply going to exacerbate the problem and increase demand.

When other neuro-divergent conditions such as ADHD and mental health disorders are increasing at a similarly overwhelming rate, and services are buckling under the strain, it’s tempting to assume the broadening of diagnostic criteria and increased awareness is all to blame. However, it is clear that the full range of other environmental factors, both immediate and long term should be seriously considered as contributing to this increase. These are important factors to take into account not just for the sake of protecting the mental, physical and emotional health of our society today but also for ensuring we protect subsequent generations from an increased predisposition to neuro-developmental disorders that may have the potential to become more severe and more prevalent in the future.

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