Question: Is the cause of ADHD more effected by genetic or environmental factors?
Current topic: Research about the environmental factors and their effect on ADHD.
Research findings:
After finding the impacts of genetic effects on ADHD, I was ever more curious about the environmental factors and their effect on ADHD symptoms, and through my research I have concluded that environmental factors, like genetic factors, are just as likely to impact a person to have ADHD (Agnew-Blais et al. 2022) (Huang et al. 2016) (Mulligan et al. 2013) (Purece et al. 2024) (San Mauro Martin, 2018) (Schantz, 2010) (Sibley et al. 2020) (Verner et al. 2015). Moreover, it is like genetic factors, researchers are still struggling to pinpoint the exact reason for ADHD symptoms, as results of certain environmental factors (Agnew-Blais et al. 2022) (Huang et al. 2016) (Mulligan et al. 2013) (Purece et al. 2024) (San Mauro Martin, 2018) (Schantz, 2010) (Sibley et al. 2020) (Verner et al. 2015).
A study intended to find the genetic risk of ADHD have found that although genetics is an unignorable factor for causing ADHD, environmental factors are just as important when it comes to causing ADHD (Agnew-Blais et al, 2022). That household chaos would cause the child to grow up to have more ADHD symptoms than others, this would suggest that ADHD is caused by the environmental factors that a child faces growing up, especially in amidst chaos (Agnew-Blais et al, 2022).
If the child grows up with a noisy environment, or does not have a predictable daily schedule, or people in the family often rushes things, does not have an organised system of where everything is, does not give the child proper privacy, have unannounced guest visits, or visit people unannounced, the child would grow up being used to those standards, leading them to have more ADHD symptoms than others (Agnew-Blais et al. 2022).
The same study would also prove that if a child, with ADHD, grows up, would also have a chaotic household themselves, which creates a seemingly endless cycle of ADHD in the family, caused by both genetic and environmental factors (Agnew-Blais et al, 2022).
When delve deeper into the lives of those who grows up in a chaotic household and would later have ADHD symptoms, they would have above average ADHD symptoms than other people diagnosed with ADHD, who lived in a less than chaotic household (Agnew-Blais et al. 2022). Moreover, they would not only have more ADHD symptoms than others, they would also experience a slower decline in ADHD symptoms as they grow older, which suggests that house hold chaos, or environmental factors, would cause the ADHD symptoms to be more implanted into their brains and their daily behaviours (Agnew-Blais et al. 2022).
In a study of Mexican children, they have found that a 1 mg/DL difference in blood lead level can cause the child to be more hyperactive and impulsive than others, suggesting the environment and the qualities of their food and drinking water can be a factor of the child’s ADHD symptoms growing up (Huang et al. 2016).
However, in the same study, it is clear that the blood lead content is not related to the child exerting inattentive symptoms and other ADHD behaviours other than hyperactivity and impulsiveness, suggesting that there may be more environmental or genetic factors who are responsible for the other ADHD symptoms (Huang et al. 2016).
In a study with children with ADHD and their siblings, the researchers found that environmental factors and the gender of the children was responsible for 30% of the ADHD symptoms in the children with ADHD, and oppositional symptom found in their siblings (Mulligan et al. 2013). This means that the environment that the child grows up in, and if they would have siblings, would contribute to them having ADHD symptoms, or more likely to have a worse case of ADHD due to their siblings’ reactions to them (Mulligan et al. 2013).
In the same study, it is shown through a parent rated ADHD test, that the siblings of the ADHD participants would have above average ADHD symptoms, more hyperactive and impulsive, than the control groups of siblings, suggesting that having an ADHD family member might also result in the rest of the family developing little ADHD symptoms, above average, but not yet to be diagnosed with ADHD (Mulligan et al. 2013).
In a study about European people with ADHD and those without, suggested that the exposure to pyrethroids can cause the person to have a higher chance of showing ADHD symptoms, 1 in 5 cases of ADHD caused by exposure to pyrethroids for France, Iceland, Switzerland, Germany and Israel, 1 in 14 cases for a group of randomly selected participants (Purece et al. 2024). Suggesting that environmental factors like exposure to pyrethroid can cause a person to be at a higher risk of developing ADHD symptoms, showing both the harm of pyrethroids on human and environmental effects of it on ADHD (Purece et al. 2024).
In the same study, it is suggested that the difference in results from European countries and the group of randomly selected participants, is the total exposure of pyrethroids there is for their country, for instance, France had 1393 cases of ADHD participants who were effected by pyrethroids, but Iceland only had 4 cases, it could be argued that the experiment did not cover enough samples from across the Europe, for the difference in data between countries are quite large (Purece et al. 2024).
In a study about the Mediterranean diet’s effect on ADHD symptoms, they found that the children diagnosed with ADHD often had lower vegetable intake, reduced intake of fish, rice, and pasta than the children without ADHD, suggesting that the difference in diet could cause the child to exert more ADHD symptoms than others, which is an environmental factor (San Mauro Martin, 2018).
In the same study, they have suspected that there may have been amore differences in ADHD symptoms that are caused by whether or not the mother had been a smoker before and in the postpartum period, which had been suspected to also increase the child’s likeliness to develop ADHD symptoms (San Mauro Martin, 2018).
Moreover, in the same study, they have suggested that having a single mother or experiencing parents separation and or divorce, have a noticeable impact on the child’s mental health and their likelihood to have lower decline in ADHD symptoms than other when they are older, and to keep more of their ADHD symptoms with them for longer period of their life (San Mauro Martin, 2018).
A review study about ADHD, the researcher found that prolonged exposure, or environmental exposures growing up, to polychlorinated biphenyls (PCB) would affect the person or the animal’s cognitive and executive function, which are the primary ADHD symptoms (Schantz, 2010). And when a child grows up being exposed to PCBs, they would in turn have a higher chance of showing ADHD symptoms than others who are not growing up exposed to PCBs (Schantz, 2010).
The same study showed that exposure to both PCBs and lead is very sensitive, often the ±1 mg/DL difference in exposure can cause dramatic spikes in ADHD symptoms shown, where kids would start having trouble with their working memory, and sometimes their spatial awareness (Schantz, 2010).
In the same study, the researcher has also suggested that the difference in ADHD symptoms between person and person, could be the result of the chemicals that they were exposed to growing up, and around them (Schantz, 2010).
Environmental effects would also result in different ADHD and life experiences of those with ADHD, in a study with late on-set ADHD participants and those who are diagnosed early on in their life, they have identified the difference in ADHD through life experiences (Sibley et al. 2020). The ADHD participants who are diagnosed later all had parents with higher academic expectations, and in turn had gotten a lot of mistreatments from their parents and peers because of their inability to focus and achieve the academic success that they are expected to achieve, which resulted in them showing a slower decline in ADHD symptoms for them (Sibley et al. 2020).
In the same study, it is found that the ADHD participants who are diagnosed later, all had been exposed to different types of traumas growing up, due to their ADHD, which had caused them to have a below average metacognition than others, along with being less academically motivated than their early on-set counterparts (Sibley et al. 2020). Moreover, they have also found that the later diagnosed ADHD participants have more severe symptoms than others who are diagnosed earlier, suggesting that their unfair treatment in their home have caused their ADHD symptoms to worsen (Sibley et al. 2020).
In the same study, they have conducted a check-up with the participants 1 year later, where they have found that 67% of the participants who are diagnosed later have now even more severe symptoms of ADHD, this could suggest that the resentment from those participants for their mistreatments early on in life have made their ADHD worse (Sibley et al. 2020).
In a study with the measurement of the child’s postnatal PCB levels and their 8-year-old behaviours, have linked ADHD symptoms with the elevated exposure of PCB in the postpartum period, where 38 ng/g of PCB exposure had the child showing ADHD symptoms at 8 year old, suggesting that the environmental effects of ADHD could be from the chemical exposures that the child face (Verner et al. 2015).
For the next round of research, I plan to research about both the environmental factors and the genetic factors and their effect on ADHD symptoms, and to compare their importance to developing ADHD symptoms. This will help me understand which one is truly more important for the development of ADHD symptoms, if any of them is important than another. This will help me understand the primary causes of ADHD, and with this knowledge, I hope future me can find a potential solution or cure for ADHD, and also helping me form the conclusion whether environmental factors or genetic factors are more important to developing ADHD symptoms.
References:
Agnew-Blais, J. C., Wertz, J., Arseneault, L., Belsky, D. W., Danese, A., Pingault, J.-B., Polanczyk, G. V., Sugden, K., Williams, B., & Moffitt, T. E. (2022). Mother’s and children’s ADHD genetic risk, household chaos and children’s ADHD symptoms: A gene-environment correlation study. Journal of Child Psychology and Psychiatry, and Allied Disciplines, 63(10), 1153–1163. https://doi.org/10.1111/jcpp.13659
Huang, S., Hu, H., Sánchez, B. N., Peterson, K. E., Ettinger, A. S., Lamadrid-Figueroa, H., Schnaas, L., Mercado-García, A., Wright, R. O., Basu, N., Cantonwine, D. E., Hernández-Avila, M., & Téllez-Rojo, M. M. (2016). Childhood blood lead levels and symptoms of attention deficit hyperactivity disorder (ADHD): A cross-sectional study of Mexican children. Environmental Health Perspectives, 124(6), 868–874. https://doi.org/10.1289/ehp.1510067
Mulligan, A., Anney, R., Butler, L., O’Regan, M., Richardson, T., Tulewicz, E. M., Fitzgerald, M., & Gill, M. (2013). Home environment: Association with hyperactivity/impulsivity in children with ADHD and their non-ADHD siblings. Child: Care, Health and Development, 39(2), 202–212. https://doi.org/10.1111/j.1365-2214.2011.01345.x
Purece, A., Thomsen, S. T., Plass, D., Spyropoulou, A., Machera, K., Palmont, P., Crépet, A., Benchrih, R., Devleesschauwer, B., Wieland, N., Scheepers, P., Deepika, D., Kumar, V., Sanchez, G., Bessems, J., Piselli, D., & Buekers, J. (2024). A preliminary estimate of the environmental burden of disease associated with exposure to pyrethroid insecticides and ADHD in Europe based on human biomonitoring. Environmental Health : A Global Access Science Source, 23(1), 91. https://doi.org/10.1186/s12940-024-01131-w
San Mauro Martín, I., Blumenfeld Olivares, J. A., Garicano Vilar, E., Echeverry López, M., García Bernat, M., Quevedo Santos, Y., Blanco López, M., Elortegui Pascual, P., Borregon Rivilla, E., & Rincón Barrado, M. (2018). Nutritional and environmental factors in attention-deficit hyperactivity disorder (ADHD): A cross-sectional study. Nutritional Neuroscience, 21(9), 641–647. https://doi.org/10.1080/1028415X.2017.1331952
Schantz, S. (2010). ADHD and Environmental Risk Factors, with Susan Schantz. EHP Publishing, 2010(1). https://ehp.niehs.nih.gov/doi/10.1289/ehp.trp120110.
Sibley, M. H., Ortiz, M., Graziano, P., Dick, A., & Estrada, E. (2020). Metacognitive and motivation deficits, exposure to trauma, and high parental demands characterize adolescents with late-onset ADHD. European Child & Adolescent Psychiatry, 29(4), 537–548. https://doi.org/10.1007/s00787-019-01382-w
Verner, M.-A., Hart, J. E., Sagiv, S. K., Bellinger, D. C., Altshul, L. M., & Korrick, S. A. (2015). Measured prenatal and estimated postnatal levels of polychlorinated biphenyls (pcbs) and adhd-related behaviors in 8-year-old children. Environmental Health Perspectives, 123(9), 888–894. https://doi.org/10.1289/ehp.1408084