Transcranial Magnetic Stimulation For ADHD

Overview

Given that the CDC confirmed that, between 2016 and 2019, approximately 6 million children were diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) in the US alone¹, it raises the inevitable question: what happens to the 30% struggling with ADHD who do not respond effectively to standard psychopharmacological treatments?²

ADHD is a neurodevelopmental disorder characterised by a persistent pattern of predominant inattentiveness, hyperactivity/ impulsiveness or a combination of them all.³ These symptoms can impede one's ability to perform day-to-day activities and tasks and develop socially, economically, and academically- all of which can significantly affect their quality of life.⁴ A Scottish study between 2009 and 2013 showed that the 1% of children diagnosed and treated with ADHD were:

• More than three times as likely to academically underperform
• More than twice as likely to leave school before the age of 16
• 40% more likely to be predisposed to unemployment⁵

While psychopharmacological drugs are the current standard, transcranial magnetic stimulation (TMS) has become more familiar in the community for the treatment of various neuropsychiatric illnesses. TMS involves the stimulation of specific regions in the brain to modulate cortical excitability; the electric pulse stimulator passes electric currents through the conductive wires of electromagnetic coils to the brain, inducing a high or low-intensity magnetic field.⁶ Scientific research on the efficacy of TMS for ADHD is novel but has shown promising results as an alternative to the standard treatment.

Understanding ADHD

As previously stated, ADHD symptoms are characterised into two main groups: inattentiveness and hyperactivity/ impulsiveness. Examples of inattentiveness include:

• Difficulty paying attention to tasks, conversations or reading
• Easily distracted by their own thoughts or external stimuli
• Seem forgetful
• Difficulty organising work/ tasks, their schedule and sticking to it

Examples of hyperactivity/ impulsiveness include:

• Fidgeting 
• Feelings of restlessness, including being unable to sit still or wait their turn
• Excessive talking and interrupting conversations 
• Difficulty waiting their turn⁷

While these symptoms can improve with age, they can also change by switching from predominantly impulsive symptoms to hyperactive, or vice versa. Diagnosis usually examines the behaviour under the age of 12, starting as early as 3; for adults seeking diagnosis and treatment, specialists would assess their symptoms from their childhood.³ A general benchmark for the diagnosis of ADHD is:

1. Presence of at least six symptoms of inattentiveness and/or hyperactivity/ impulsiveness up to age 16
2. Or at least 5 symptoms of inattentiveness and/or hyperactivity/ impulsiveness for age 17 and older
3. Symptoms last at least 6 months
4. Ruling out other disorders that display similar symptoms
5. Symptoms do not reflect the individual's expected developmental level
6. Symptoms are present in at least two distinct settings 
7. Interferes with social relationships, academic progress and/or professional environment⁸

Unfortunately, ADHD is often undiagnosed and undertreated. 

Standard psychopharmacological treatments include stimulants and non-stimulants. While stimulants (e.g. amphetamines and methylphenidates) block the reuptake of dopamine at the pre- or post-synaptic membrane to increase dopamine levels in the brain, non-stimulants (e.g. alpha-agonists and antidepressants) target other neurotransmitters like norepinephrine by their adrenoceptors to enhance attention.⁹ Stimulants are typically the first line of treatment but can be changed to a non-stimulant in the case of adverse side effects.

Due to their similar pathophysiology, stimulants may exacerbate or be the cause of a tic disorder in patients with ADHD; in this case, a healthcare professional may advise the patient to switch to an alpha agonist or the antidepressant atomoxetine to reduce the frequency of the tics.¹⁰ An alternative treatment plan to consider is to start with a non-stimulant for it is effective for both tic disorders and ADHD; then there is the option to switch to a stimulant if the severity of their ADHD symptoms outweigh their tics.¹¹ 

People being treated for their ADHD with psychopharmacological drugs may also be at higher risk of cardiovascular disease. A Swedish study of 278,027 people diagnosed with ADHD between the ages 6 and 64 showed that with each year, the risk of cardiovascular disease increased by 4% and, after the first three years, by 8%.¹² These findings highlight the urgent need to find an alternative treatment option that has minimal effect on other disorders, minimal side effects, and reduced risk of health complications.

Introducing TMS as a novel therapy for ADHD

Transcranial magnetic stimulation is a non-invasive procedure in which a magnetic field generated by the electric pulse stimulator is used to pass an electric current from the primary coil from the machinery to activate the secondary coils (nerve cells) in targeted regions of the brain.¹³ By modulating the frequency, intensity and targeted regions of the brain, TMS can regulate the synaptic communication between neurons of various neuropsychiatric conditions.⁶ For the time being, this medical procedure has been selectively FDA-approved in clinical practice for the treatment of:

• Major depressive disorder (MDD)
• Obsessive-compulsive disorder
• Smoking cessation
• Anxiety disorder alongside MDD
• Migraines¹⁴

Granted, TMS has shown promising results for these health concerns. However, because a large population of ADHD patients are children, the efficacy and application of TMS for the treatment of ADHD is still up for debate. To demonstrate the efficacy and safety of any treatment, it is important to evaluate whether the research made is reliable and abundant. For instance, a random and double-blinded clinical trial is more reliable than a questionnaire as it eliminates the possibility of bias in the results.

A large number of clinical trials conducted by several researchers will yield more authentic results. As of now, the scientific research on the use of TMS for treating ADHD is not large enough to make any definitive conclusions on its efficacy and safety.

Scientific literature on TMS for ADHD

Amid the debates regarding the efficacy of TMS for ADHD, the benefits should still be assessed as it would be instrumental in expanding the treatment options to help a larger group of people struggling with the neurodevelopmental disorder.

A randomised, sham-controlled pilot study in 2012 measured the Clinical Global Impression (CGI)- commonly used in research to quantify the severity or improvement of a patient's illness- of nine adolescents and young adults with ADHD. After completing ten sessions of TMS in two weeks, Weaver et al.¹⁵ found there to be no serious side effects or discontinuation of the sessions throughout the study.

In terms of efficacy, they did not see a significant difference between the sham and TMS groups- even though the CGI significantly improved both. These findings may be limited due to the short time frame of the study. By extending the study for a few years, a more accurate representation of the CGI and risk of side effects may appear from TMS treatment. 

A decade later, a meta-analysis of 189 children/ adolescents and adults- with an average age of 8.53 years and 32.78 years, respectively- published by Chen et al.¹⁶ showed that repetitive TMS (rTMS) significantly improved attention and the cognitive function of processing information quickly. While it suggests that rTMS can reduce symptoms of ADHD, the randomised clinical trials used in the meta-analysis are subjected to publication bias and imprecision according to the Cochrane risk of bias assessment. What this means as a consumer of scientific literature is that you should accept these results with a certain degree of scepticism.

Limitations of TMS

Ultimately, further research is needed to better understand the effects of TMS on ADHD, particularly randomised, double-blinded, sham-controlled clinical trials and large-scale reviews. What can be criticised about the procedure is that it lacks accessibility.

In comparison to just taking a pill, some people may be reluctant to dedicate 30 minutes a day, for a few days a week, to have the procedure. Additionally, the time spent to travel to the facility and wait may all be a deterrent for some. Hence, stimulants and non-stimulants may save more time in comparison to TMS.

In terms of cost-effectiveness, it is unclear where the balance weighs heaviest in the treatment of ADHD. Nonetheless, a long-term economic analysis has shown that, after no response to an antidepressant, TMS was more cost-effective than prescribing antidepressants again in patients with MDD.^17,18

A meta-analysis of randomised, double-blind and sham-controlled studies¹⁹ for the effect of rTMS on depression found that the most common side effects were headaches and discomfort. This supports the understanding that TMS can cause local pain in the form of a headache; the procedure can also cause:

• Neck pain
• Tinnitus 
• Reduced tolerance to sound (hyperacusis)⁶

If the appropriate precautions are not taken, TMS can also cause hearing loss and seizures. Though it is rare, they can still be avoided by following the guidance provided: abstaining from alcohol and wearing earplugs can lower the risk of seizures and hearing loss respectively.²⁰ Ultimately, further research is required to assess the extent of the side effects of TMS in patients with ADHD, particularly in randomised, double-blinded and sham-controlled clinical trials and large-scale reviews. There are fewer side effects recorded for TMS in comparison to the psychopharmacological drugs.

FAQs

Can TMS be combined with another treatment for ADHD treatment?

After a 1-month follow-up, a randomised, double-blinded, and sham-controlled clinical trial of 60 children²¹ concluded that combining rTMS with the non-stimulant atomoxetine was significantly more effective in reducing the CGI and overall severity of ADHD symptoms.

Another clinical trial assessing the efficacy of TMS combined with atomoxetine for ADHD in children had the same outcome;²² they used the SNAP-IV test, a tool praised for its high sensitivity in screening for ADHD symptoms in children²³, before and after the treatment groups to find that the combination of TMS with atomoxetine was more effective than either of the treatments on their own.

However, it is vital that you contact your general practitioner about possibly combining TMS with another drug as there is not enough information on the mechanism of how they interact in the human body. 

Have there been any developments in TMS?

Despite being only invented about 40 years ago by Anthony Barker and his team²⁴, there have been rapid advancements in the stimulator’s ability to specifically target regions in the brain. A 2023 review²⁵ quotes that there is potential for it to change the cortical excitability of specific regions to improve the connectivity of the synaptic neurones.

This can be done by incorporating neuroimaging and MRI techniques to enhance the precision of TMS. Regardless, we are still in the early years and can only anticipate any advancements in the personalisation and sensitivity of TMS.

Summary 

As medicine continues to expand, incorporating physics with biology to optimise the efficacy of the treatment, we reflect on the medicine that came before and wonder: which is superior? While TMS has shown efficacy in reducing symptoms of ADHD- all while having fewer side effects- there is not enough conclusive research to confidently point to one as the winner. As always, you should consult a general practitioner to discuss whether or not TMS is an appropriate and affordable route for you or your children.