ADHD (Attention Deficit Hyperactivity Disorder) is a neurological condition that is characterised by cognitive dysfunction in certain areas such as memory and attention, as well as behavioural difficulties with impulsivity and hyperactivity. While there is growing scientific understanding of ADHD signs and symptoms, there are still many questions regarding what causes ADHD. People often ask: is ADHD inherited, or could there be other causal factors which contribute to its development? Symptoms of ADHD appear in early childhood but can still be prevalent in later life leading to diagnosis of ADHD in Adults.
In a family where one person is diagnosed with ADHD, It is likely that one or both of the parents would meet the criteria for an ADHD diagnosis. Therefore, for many, there exists an indication that ADHD has a genetic origin. However, information provided by the NHS website supports that as well as genetics, other factors such as brain function, brain structure and belonging to a predisposed group may, in some combination, contribute to the presentation of ADHD.
Since ADHD is a complex condition, many alternative ideas still circulate regarding its origins. Some scientists propose that factors such as toxins, nutrition or environment are likely to play a role in the development of ADHD. However, it is important to note that these claims are not always supported by substantial clinical data. We discuss the role of genetics in the development of ADHD, and these additional claims, below.
Clinical data indicates that ADHD tends to run in families, suggesting that ADHD is at least partly inherited. One study revealed that a majority of identical twins share ADHD tendencies, and it has also been observed that up to 33% of fathers who had ADHD in their younger years have children who also live with ADHD. This all gives credence to the idea that ADHD can be inherited. There are widespread efforts aimed at identifying the specific genes that play a role in the development of ADHD, and The National Human Genome Research Institute believes that ADHD may be linked to at least two different genes.
There is strong evidence to suggest that ADHD is inherited and the symptoms are at least partially genetic. However, this evidence is not conclusive – not every member of a family will inherit ADHD from their parents, or a previous generation. So, in addition to a possible genetic origin, there is growing research on external factors that may cause ADHD. The answer to the question: “is ADHD inherited?”, therefore, is yes, it can be; but there are likely to be other causes too.
Due to modern manufacturing processes, chemicals are all around us. Some controversy surrounds certain chemicals present in everyday products, such as PFCs (perfluorochemicals, coated on surfaces like tupperware or carpets to increase resistance to grease, stains, and water), triclosan (used in hygiene and cosmetic products to reduce the risk of bacterial contamination) or BPA (bisphenol A, needed to manufacture polycarbonate plastics typically found in food and drink containers). It is theorised that substances such as these may contribute to the development of ADHD by disrupting brain development in the first trimester of pregnancy, as it is during this time that many crucial connections between neurons develop. In 2010, the Learning and Developmental Disabilities Initiative identified a number of household chemicals which were linked to ADHD, along with other developmental disorders. However, the evidence was not conclusive. Of the many millions of people exposed to these chemicals, only a very small proportion would develop ADHD. Therefore it is at least unlikely that contact with these chemicals would be the only cause of ADHD.
Others question whether nutrition and diet may contribute to the development of ADHD. It should be noted that there has been no substantive evidence to support this theory. Despite this, in some households the 40-year-old Feingold Program, which advocates for strict regulation of certain food additives (artificial food dyes, flavourings and sweeteners, as well as the preservatives TBHQ, BHA and BHT) as a means of preventing ADHD, is still in use. The Feingold Program comes under criticism as extremely prohibitive and impractical, and tends to focus on a perceived ‘cure’ for ADHD rather than management of its symptoms.
Although controversial, there are newer theories which claim that ADHD may derive from the inherent nature of modern society. Michael Ruff, M.D. asks whether the high-stress, consumerist context of our culture may lead to the development of ADHD. Ruff argues that modern children grow up in a fast-paced environment which can make it challenging to concentrate or focus. He points to anecdotal data, mostly seen in children’s classroom behaviour. However, though modern society may lead people to exhibit behaviours similar to those seen in ADHD, there is no evidence to suggest that it actually causes it. More likely is that our culture can at times create an inherent sense of urgency, trigger a lack of focus, or drive hyperactivity.
While there are several competing theories and ideas for the causes of ADHD, most evidence-based theories suggest that there is a genetic and neurological origin. With that said, it is important to note that although we may not have conclusive evidence for external factor theories, it can be helpful to adopt healthy lifestyle choices so as not to exacerbate ADHD or ADHD-like symptoms.
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