Genetic Causes of ADHD

Understanding ADHD

Over the past few years, Attention-deficit/hyperactivity disorder (ADHD) has gained traction and curiosity among both adults and adolescents. But what exactly does it entail? Is it the same as being restless or ‘hyper’? While the name may seem self explanatory, in simple terms ADHD is a condition that impacts behaviour. It is generally characterised by hyperactivity, impulsivity and difficulty focusing (inattention). Prevalence of ADHD often becomes apparent in childhood, especially in children between the ages of 9 and 10.

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‍Nevertheless, ADHD also impacts adults and may appear to be different for men and women (To read more about ADHD in adults, click here and to read more about ADHD in women, click here). Regardless of the age or gender, living with ADHD impacts various aspects of life such as school, family and work.

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With an increased interest in understanding ADHD, there are now regrettably greater misconceptions about what the causes might be. There is a tendency to attribute ADHD to poor parenting or to blame the child/person with ADHD for being ‘too lazy’ or not working hard enough. Such misinformation amplifies stigmas associated with this condition and makes it even more difficult for individuals with ADHD to cope with their symptoms. Thus, it becomes important to refer to empirical evidence to understand ADHD.

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Genetic Basis of ADHD

While the causes of ADHD are yet to be fully recognised by researchers, there is strong evidence to suggest that it has genetic links. Nevertheless, given its complex nature, there is also some research to support environmental sources that may cause ADHD.

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Heritability of ADHD

Heritability is defined as the extent to which a characteristic is transmissible from parents to their children. A meta analysis in 2018 revealed that the heritability of ADHD could be high as 77–88%. Heritability has traditionally been determined by studying both families (i.e parents and their children) and twins to understand whether a condition can be attributed to the environment or to genetics (Faraone and Larsson, 2019).  

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Family Studies

Family studies play a crucial role in understanding the genetic component of ADHD as they aim to examine the prevalence of ADHD within families to determine if there is a hereditary pattern. Studies dating back to the 1990s have found that children with ADHD are more likely to have first-degree relatives (parents or siblings) with ADHD as compared to their peers. To establish cross-cultural prevalence (especially within Asian populations), a 2008 study found similar heritability patterns with Chinese nationals (Faraone et al., 1995).  

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Twin Studies

Another common technique to establish heritability was is by studying identical twins and fraternal twins. Studies have found that the likelihood that both twins in a pair will have ADHD, are higher in identical twins compared to fraternal twins. This supports the idea that genetic factors contribute to the risk of developing ADHD. Studies in adult twins (2018) and cross-cultural twins (2013) have also supported the claim of heritability of ADHD and its prevalence right into adulthood and across ethnicities and cultural backgrounds (Brikell et al., 2021; Chang et al., 2013). 

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Thus, family and twin studies collectively support the notion that ADHD is a complex disorder with a strong genetic component.

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ADHD and the Brain 

While the specific genes that cause ADHD are still unknown, neuroimaging techniques have revealed differences in the brain structures of those with ADHD in comparison with those without ADHD. A study in 2015 found that certain structures of the brains of children with ADHD were about 5% smaller than their peers. Moreover, both children and adults with ADHD are found to have lower levels of dopamine than the general population (). Such images suggest that as a disorder, ADHD affects both the brain and the nervous system. 

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Implications and Conclusions

The above information about ADHD and its genetic roots may appear overwhelming and disempowering at first. Some may wonder ‘Does this mean that my child is bound to have ADHD if I have a diagnosis?’ or ‘Is there anything I can do to stop these genes from being transmitted to me or to my children?’ Living with ADHD can be difficult as it has implications for everyday activities, making them more challenging. While there isn’t necessarily a “cure” for ADHD, there are several ways in which the symptoms can be managed.

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‍Research has found exercising to have a positive impact on persons with ADHD as it helps increase dopamine in the body. In addition, creating a routine can be beneficial for both children and adults with ADHD. Prominent research has also found that medication alongside behaviour therapy can be effective in managing symptoms of ADHD.

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If you are keen to know about medications available in India, click here for a consultation with our psychiatrists. Additionally, you may choose to book an appointment with our psychologists to understand how behaviour therapy can help you or your child cope with ADHD.   

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References 

Brikell, I., Burton, C., Mota, N. R., & Martin, J. (2021). Insights into attention-deficit/hyperactivity disorder from recent genetic studies. Psychological medicine, 51(13), 2274-2286.

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Chang, Z., Lichtenstein, P., Asherson, P. J., & Larsson, H. (2013). Developmental twin study of attention problems: high heritabilities throughout development. JAMA psychiatry, 70(3), 311-318

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Faraone, S. V., Biederman, J., Chen, W. J., Milberger, S., Warburton, R., & Tsuang, M. T. (1995). Genetic heterogeneity in attention-deficit hyperactivity disorder (ADHD): gender, psychiatric comorbidity, and maternal ADHD. Journal of abnormal psychology, 104(2), 334.

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Faraone, S. V., & Larsson, H. (2019). Genetics of attention deficit hyperactivity disorder. Molecular psychiatry, 24(4), 562-575.

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Singh, A., Yeh, C. J., Verma, N., & Das, A. K. (2015). Overview of attention deficit hyperactivity disorder in young children. Health psychology research, 3(2).