Another off-label yet encouraging use of TMS is for treating attention deficit/hyperactivity disorder (ADHD or ADD).
ADHD is the most common behavioral disorder. A staggering 6.1 million (9.4%) kids in the United States have at one time been diagnosed with ADHD, according to a 2016 survey from the Centers for Disease Control and Prevention (CDC). The condition affects boys more often than girls.
Childhood ADHD may continue into adulthood in around one-third of cases. However, the percentage of American adults affected by ADHD is variable. A 2019 study estimated about 0.43% of adults had ADHD in 2007, with the rate doubling to 0.96% in 2017.
What are the Signs and Symptoms of ADHD?
The tell-tale features are inattention, hyperactivity, and impulsivity.
The fifth version of the Psychiatry’s Bible — The Diagnostic and Statistical Manual of Mental Disorders (DSM-V) lists 18 symptoms for diagnosing ADHD. Of these, at least six symptoms must be present in at least one of the two domains — i.e., inattention and hyperactivity/impulsivity.
Moreover, the diagnosis of ADHD requires that these symptoms have been present for a minimum of 6 months and are severe enough to interrupt your child’s (or yours) social, academic, and/or work-related performance.
Inattention: six (or more) of the following symptoms in children aged up to 16 (or five of the following symptoms if you are a teen or adult):
- Makes careless mistakes in schoolwork, at work, or while doing other activities.
- Unable to stay focused during lectures, chats, or lengthy reading.
- Is easily side-tracked.
- Often does not seem to listen, fails to follow instructions properly, or daydreams a lot.
- Often loses personal belongings.
- Teens or adults often forget to run errands; for instance, failing to pay bills on time or keep appointments.
- Unable to finish tasks on time.
- Fails to develop good time management skills.
- Is reluctant to engage in tasks that warrant sustained mental effort.
Hyperactivity and/or Impulsivity: six (or more) of the following symptoms in children aged up to 16 (or five of the following symptoms if you are a teen or adult):
- Fidgets or squirms a lot while sitting.
- Unable to stay seated in situations when sitting is required.
- Is restless.
- Has difficulty staying silent during activities.
- Is almost always “on the go.”
- Talks excessively
- Is impatient during conversations
- Often butts into conversations or disturbs other kids during games or activities
- Is too impatient while waiting for their turn (e.g., while waiting in line)
What Causes ADHD?
The causes of ADHD are somewhat unclear. The condition appears to be a sum of genetic and environmental factors.
Most research suggests that genes and heredity play a significant role in predicting who develops ADHD. This means that ADHD is passed down from a parent or another close relative to the child. However, researchers are still exploring the role of certain genes, especially ones related to the brain chemical dopamine, in developing ADHD.
Additional evidence indicates exposure to toxins and chemicals, such as lead, as a risk factor for developing ADHD.
Babies born prematurely are also at higher risk of developing ADHD when they grow up.
Studies have found a strong connection between ADHD and weaker function and structure of the prefrontal cortex (PFC), especially on the right side. This part of the brain is the primary executive control center that helps to organize, plan, stay focused, and make decisions. Experts from the National Institute of Mental Health (NAMI) unveiled that a segment of the PFC fails to develop normally in kids with ADHD.
Limitations Associated With the Conventional Treatment for ADHD
The standard treatment for ADHD primarily include medications (stimulants and non-stimulants) as well as behavioral therapy.
Though these therapies effectively tackle ADHD symptoms in most patients, about one-third still fail to benefit from these therapies. Others quit treatment as they can’t tolerate the side effects of ADHD medications.
In such settings, alternative options like transcranial magnetic stimulation (TMS) may help to address these limitations.
How Can TMS Work for ADHD?
Given that the right PFC (rPFC) abnormality has been implicated in the disease process of ADHD, TMS may alter the abnormal rPFC activity.
This noninvasive brain stimulation may tweak the neuronal function, activity, and plasticity of the rPFC. That, in turn, may induce required alterations in attention, working memory, and executive functions, thereby reducing the symptoms of ADHD.
Evidence Supporting the Benefits of TMS in ADHD
A 2020 pilot study evaluated whether targeting the rPFC with multiple sessions of rTMS, can positively impact clinical symptoms in adults with ADHD. Participants underwent three weeks of daily high-frequency (18 Hz) rTMS sessions. Moreover, to activate the relevant brain circuitry, participants also underwent a brief computerized assessment. Researchers also used EEG to determine electrophysiological alterations induced by the treatment. The outcome was a significant improvement in ADHD symptoms after the TMS sessions.
Another group of researchers used 1 Hz rTMS over the left dorsolateral PFC in school-going kids (ages 7–12) with ADHD. This study determined the tolerability and safety of TMS in children. Nonetheless, given the significant clinical improvement of ADHD symptoms, its preliminary results also appeared promising. Still, this study had certain limitations, including the study design and small sample size.
Similarly, Brainsway — the leading brand that manufactures TMS coils — also conducted a study to evaluate the effectiveness and safety of deep TMS in 53 adult patients with ADHD. Results showed substantial improvement with deep stimulation using BrainsWay’s proprietary ADHD coil compared to the superficial stimulation with a standard figure-8 coil.
TMS as a Diagnostic Tool in ADHD
According to a review published in The Journal of Child Neurology, single-pulse and paired-pulse TMS protocols can also probe the degree of hyperactivity in ADHD patients.
One commonly used paired-pulse protocol is short-interval intracortical inhibition (aka SICI). SICI uses a TMS pulse below the threshold interrupted by a short stimulus interval of 3 milliseconds and then a suprathreshold pulse.
Studies have shown an inverse relation between SICI and hyperactivity. Low levels of SICI reflect greater hyperactivity levels in people with ADHD. Moreover, ADHD medications tend to balance out these disruptions in SICI. These facts suggest that this TMS paradigm can serve as a marker for and predict the severity of ADHD symptoms.
Are There Any Side Effects of TMS on Children With ADHD?
Although there is no evidence of any severe side effects of rTMS in children with ADHD, their brains are in sensitive periods of development.
Sensitive periods are periods during brain development when a treatment like TMS packs quite a punch on the brain. Hence, if applied correctly, rTMS can induce brain plasticity and affect brain function more stably and effectively during this period.
That said, it’s important to know the risk of inducing maladaptive brain plasticity via neuromodulation interventions.