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Attention Deficit Hyperactivity Disorder (ADHD)

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In the final part of this series, I will address another common cognitive disorder, Attention Deficit Hyperactivity Disorder (ADHD). Similar to OCD, ADHD is a widely known mental disorder that does not draw as much criticism in the eyes of the public compared to other more “taboo” disorders such as autism. In fact ADHD is one of the most common forms of mental disorders alongside OCD, affecting approximately 8.4% of children. Due to its prevalence and generally less severe side effects, ADHD has not developed the same social stigma as other mental disorders. Despite its notoriety, I similarly am still woefully uneducated in this particular disorder despite having heard about it for years. So what is ADHD? Like OCD and Autism are there different subtypes of ADHD? What is the neurobiological explanation of ADHD and whats the treatment for ADHD(If any)?

What is ADHD?

Well a good starting point would be to define the disorder. Attention-deficit/hyperactivity disorder (ADHD) is marked by an ongoing pattern of inattention and/or hyperactivity-impulsivity that interferes with functioning or development. As mentioned in its name, ADHD has 3 main component signs and symptoms.

  1. Inattention such as being unable to focus on a task and being easily distracted

  2. Hyperactivity where an individual would exhibit excessive body movement

  3. Impulsivity where a person has hasty body actions and often does things without thinking. 

It is important to note that a person exhibiting one or more of such symptoms may not necessarily have ADHD. According to the Diagnostic & Statistical Manual of Mental Disorders (DSM 5), to diagnose someone as having ADHD, symptoms need to be significantly greater than the average person and persist for at least 6 months.

Subtypes of ADHD

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In general, ADHD may be classified in 3 main subtypes depending on which is the predominant presenting symptom in an individual.

 

  1. Inattentive type

This may be classified as having a short attention span, difficulty listening to others, difficulty attending to details, easily distractible, prone to forgetting and poor organisational and studying skills depending on age group. Having listed these symptoms, I recognize also that this is a highly subjective list of symptoms as each individual will have varying degrees of attention span, focus and organisational skills. In fact, recent studies have shown that a child’s average attention span, with or without ADHD, is steadily decreasing from 12 seconds to 8 seconds. So this begs the question, do we all have ADHD? Just some to a greater extent than others?

 

  1. Impulsive-hyperactivity type

 

The impulsive nature manifests as interrupting others or blurting out answers along with impatience and irrational thinking Ie often taking risks or acting without thinking.

 

The hyperactivity portion presents itself mainly through bodily movements such as being fidgety, talking excessively and inability to focus on tasks. 


 

  1. Combined type

Lastly is the combined type which is an amalgamation of being inattentive, hyperactive and impulsive.

Comorbidity of ADHD

I touched on this in a previous article where I mentioned how it was intriguing how mental disorders seem to come as a package deals with having one disorder seemingly causing or resulting in another. Well this is no more apparent then for the case of children with ADHD.

 

More than two thirds of the children with ADHD have another mental disorder.

For psychiatric comorbidities, 21% of children with ADHD have autism, with a further 25% having some form of a learning disability, with others having intellectual disabilities or tourettes syndrome.  It is important to note that ADHD in this context is not considered a learning disability.

Non-psychiatric comorbidities include epilepsy, migraines and sleeping disorders such as insomnia.

 

So why does ADHD seem to regularly occur with other disorders? Is it a cause for other disorders or a symptom? It does seem a lot like a  chicken or the egg type situation. So lets take a close look at the neurobiological explanation of ADHD and its causes.

Neurobiology of ADHD and associated causes

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ADHD brain structure

In most ADHD patients, there is an observed reduction in volume of the left sided prefrontal cortex. This region supports the recognition of meaningful patterns in ambiguous stimuli. In layman’s terms, it helps us sieve through useful information from redundant information. Hence a reduction in this region may explain the inattentive nature of individuals with ADHD as they are more exposed to “useless” information making it harder to take it what's actually important and to stay on task. However, an explanation for the hyperactive portion has yet to be correlated with any meaningful abnormalities in brain structure from the journals I have read. 

Genetics

ADHD, like other mental disorders such as autism, exhibits a strong genetic linkage, seemingly “running in families”. Like autism, twin studies conducted for twins showed an 80% concordance for ADHD, much higher than other mental disorders. This is reinforced by the fact that adopted individuals showed a lower prevalence of ADHD as compared to their step-siblings. Hence this discredits the claim that ADHD developed as a result of an individual's environment and upbringing, further strengthening the clause for genetic lineage of ADHD. 

 

Apart from heritability, dopaminergic and serotonergic gene defects are suspected to increase the risk of ADHD. This adds weight to the comorbidity of mental disorders as a dopamine defect is the hallmark for parkinson’s disease and serotonin is theorized to be affiliated with OCD. Hence from this statement, it does seem more apparent that ADHD is more of a “backseat disorder” manifesting as sort of a symptom of other more severe disorders. 

Lastly, rare chromosomal abnormalities such as microdeletion syndrome that involves the deletion of multiple genes may also increase the risk of ADHD. 

 

Environment

Pre & perinatal risks are one suspected to increase the likelihood of ADHD.These risks include maternal smoking, substance abuse, low birth weight and prematurity. However, no causal link has yet to be established for such instances . However, given how these factors have been related to an increased risk of other mental disorders such as autism, by the transient property it would be safe to assume that a similar link can be made for ADHD. 

Environmental toxins, primarily pesticides, industrial pollutants and lead. 

Lastly family adversity which includes psychological stressors such as abuse, with a higher incidence rate of childhood abuse tied to children having ADHD. However, it is unclear, given the difficulty in managing special needs children, whether ADHD was a cause or consequence of such family adversity. Furthemore this factor has already been discredited by the previous study comparing the prevalence of ADHD in adopted children with their siblings.

ADHD Treatments

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Well given its relatively less-severe nature, not a lot of treatments are required for this disorder. Although there are ADHD medications available for those who want it, a significant proportion of individuals who have ADHD do not take any form of medication and are able to exercise self control and focus on tasks at hand. But for the sake of completeness, here’s some of the treatment methods offered. 

 

Medications such as psychostimulants can be prescribed in more severe cases of ADHD to balance the neurotransmitter levels in the brain. 

Similar to autism and OCD, behavioural therapy and social skills training can also help with management of ADHD symptoms. However both of these treatment methods do not provide long lasting relief from ADHD, but rather just help the individual cope with the disorder. In the most severe cases of ADHD, Deep brain stimulation (DBS) has been touted as a possible treatment for ADHD, though no clinical trials have been conducted yet for ADHD since its not considered a “serious debilitating disorder” along with the invasive nature of DBS.

On that note, speaking to friends who I have known for a while who have ADHD, I have also come to learn that oftentimes, ADHD is best managed through a close monitoring of one's diet and lifestyle routines. For instance, individuals with ADHD should avoid too much sugary foods or caffeine as this may exacerbate their hyperactivity.  Furthermore, regular exercise such as running or swimming can help them to improve their ability to focus as well as use up excess energy stores to reduce their hyperactive nature.

References

  1. ADHD: Recognising symptoms🌍. CAMHS Professionals. (2021, April 1). Retrieved February 19, 2022, from https://camhsprofessionals.co.uk/2021/04/01/adhd-recognising-symptoms%F0%9F%8C%8D/

  2. Bartel, G., Marko, M., Rameses, I., Lamm, C., & Riečanský, I. (1AD, January 1). Left prefrontal cortex supports the recognition of meaningful patterns in ambiguous stimuli. Frontiers. Retrieved February 19, 2022, from https://www.frontiersin.org/articles/10.3389/fnins.2020.00152/full#:~:text=Left%20Prefrontal%20Cortex%20Supports%20the%20Recognition%20of%20Meaningful%20Patterns%20in%20Ambiguous%20Stimuli,-Gr%C3%A9gory%20Bartel1&text=Processing%20of%20ambiguous%20visual%20stimuli,(PFC)%20in%20neuroimaging%20studies.

  3. Increase in ADHD diagnosis, latest average attention span statistics. LDRFA. (2021, April 13). Retrieved February 19, 2022, from https://www.ldrfa.org/increase-in-adhd-diagnosis-the-latest-average-attention-span-statistics/

  4. Larry Silver, M. D. (2021, December 1). ADHD medications for adults and children: Add stimulants, nonstimulants & more. ADDitude. Retrieved February 19, 2022, from https://www.additudemag.com/adhd-medication-for-adults-and-children/

  5. Larry Silver, M. D. (2022, February 18). Executive dysfunction, explained! ADDitude. Retrieved February 19, 2022, from https://www.additudemag.com/executive-function-disorder-adhd-explained/

  6. Neurobiology of attention deficit hyperactivity disorder (ADHD) - A Primer. Psych Scene Hub. (2021, October 27). Retrieved February 19, 2022, from https://psychscenehub.com/psychinsights/neurobiology-of-adhd/

  7. U.S. Department of Health and Human Services. (n.d.). Attention-deficit/hyperactivity disorder. National Institute of Mental Health. Retrieved February 19, 2022, from https://www.nimh.nih.gov/health/topics/attention-deficit-hyperactivity-disorder-adhd

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