Deep transcranial magnetic stimulation (deep TMS) is a noninvasive brain stimulation treatment that uses magnetic pulses to reach structures 4 to 6 centimeters below the skull’s surface. That’s roughly twice the depth of standard TMS, which typically penetrates only 2 to 2.5 centimeters. The technology was developed to treat conditions rooted in deeper brain circuits, and it’s currently FDA-cleared for major depressive disorder, obsessive-compulsive disorder, and smoking cessation.
How Deep TMS Works
All forms of TMS work on the same basic principle: a coil placed against the scalp generates a magnetic field, which passes through the skull and creates tiny electrical currents in brain tissue. These currents activate or calm specific neural circuits depending on where the coil is aimed and how the pulses are delivered.
What separates deep TMS from standard TMS is the coil design. Standard TMS uses a figure-8 shaped coil, two small circular loops of wire sitting flat against the head. This design focuses energy on a narrow, shallow area of the brain’s outer surface. Deep TMS uses what’s called an H-coil, a larger, more complex structure with winding patterns that wrap around multiple sides of the head. By positioning wire elements at different locations around the skull, all carrying current in the same direction, the H-coil creates overlapping magnetic fields that add together at depth. The result is stimulation that reaches brain regions 4 to 6 centimeters in, compared to the 2 to 2.5 centimeters typical of standard coils.
This deeper reach matters because conditions like OCD and addiction involve circuits buried in the brain’s interior, areas that a standard coil simply can’t activate with enough strength to produce a clinical effect.
What Deep TMS Treats
Major Depressive Disorder
Depression was the first condition cleared for deep TMS treatment, and the evidence base is the largest. In the pivotal trial by BrainsWay (the company that manufactures the H-coil system), 37% of patients responded to active treatment compared to about 28% receiving a sham treatment, and 30.4% achieved remission versus 15.8% in the sham group. These trials specifically enrolled people who hadn’t improved enough on antidepressant medications, so these are patients already considered harder to treat.
Real-world results tend to look even better. A large observational study tracking over 5,000 patients found response rates between 58% and 69%, with remission rates of 28% to 36%. The gap between controlled trials and clinical practice likely reflects the fact that real-world clinicians can adjust treatment more flexibly than rigid study protocols allow. Deep TMS is also cleared for reducing anxiety symptoms in people whose depression comes with significant anxiety, which is the majority of depression cases.
Obsessive-Compulsive Disorder
In 2018, the FDA cleared deep TMS for OCD, making it the first noninvasive device approved for the condition. The pivotal trial measured symptom severity using a standard clinical scale. Among patients receiving active deep TMS, 38.1% achieved at least a 30% reduction in symptom severity, compared to just 11.1% receiving sham treatment. More than half of the active group (54.8%) achieved at least a partial response, defined as a 20% or greater reduction in symptoms. For a condition that’s notoriously difficult to treat, those numbers represent a meaningful option for people who haven’t responded well to medication or therapy alone.
Smoking Cessation
The most recent FDA clearance targets smoking addiction. The treatment works by stimulating the prefrontal cortex and the insula, a deeper brain region involved in cravings and interoceptive awareness (your brain’s sense of what’s happening inside your body). In the clinical trial, 17.1% of patients in the active treatment group achieved a continuous quit lasting at least four weeks, compared to 7.9% in the sham group. That may sound modest, but smoking cessation rates for any single intervention tend to be low, and deep TMS is typically used alongside other quit strategies.
What a Treatment Course Looks Like
A typical deep TMS treatment course spans about 12 weeks and is divided into two phases. The first phase is intensive: 20 sessions over 4 weeks, meaning you go in five days a week. The second phase tapers to twice a week for another 8 weeks. That’s 36 sessions total.
Each session lasts roughly 20 minutes. You sit in a chair, a cushioned helmet containing the H-coil is positioned on your head, and the device delivers pulses in a pattern of brief bursts followed by pauses. You’re awake the entire time with no sedation, and you can drive yourself home afterward. Before the first treatment session, your clinician calibrates the device by finding your “motor threshold,” the minimum magnetic intensity needed to make your thumb twitch. This personalized measurement ensures the pulses are strong enough to be effective without being unnecessarily intense.
Most people notice results starting around week 2 to 4 of treatment, though this varies. Unlike medication, deep TMS has no systemic effects on the rest of your body since the magnetic field is targeted only to the brain.
Side Effects and Safety
The most common side effects are scalp discomfort, headache, and tingling or twitching of facial muscles during treatment. These are generally mild, improve shortly after the session ends, and tend to decrease over the course of treatment as you acclimate.
The most serious potential risk is a seizure, but this is rare. Lightheadedness can also occur. Hearing protection (earplugs or similar) is provided during sessions because the coil produces a loud clicking sound, and inadequate ear protection could theoretically contribute to hearing issues over many sessions.
People with certain metal objects in or near the head are not eligible for deep TMS. Metallic cranial implants, aneurysm clips, and certain other ferromagnetic devices can heat up or shift position when exposed to strong magnetic fields. Titanium skull plates and some MRI-compatible stents may be evaluated on a case-by-case basis, but the general rule is that any metal in the head needs careful screening before treatment. Cochlear implants, cardiac pacemakers, and other implanted stimulators are also typically disqualifying.
Deep TMS vs. Standard TMS
The practical differences between deep TMS and standard repetitive TMS (rTMS) come down to three things: depth of stimulation, session length, and the conditions they treat. Standard rTMS reaches about 2 to 2.5 centimeters into the brain and is primarily used for depression, targeting the left dorsolateral prefrontal cortex on the brain’s outer surface. Deep TMS reaches 4 to 6 centimeters and can target structures involved in OCD, addiction, and other conditions that standard coils can’t effectively reach.
Session times for deep TMS are typically around 20 minutes. Standard rTMS sessions historically ran 30 to 40 minutes, though newer accelerated protocols have shortened that considerably. The side effect profiles are similar for both, with scalp discomfort and headache being the most common complaints. Neither requires anesthesia, and neither has the systemic side effects associated with psychiatric medications like weight gain, sexual dysfunction, or fatigue.
The broader stimulation field of deep TMS does come with a trade-off: because the H-coil activates a wider volume of brain tissue, it’s less focal than a figure-8 coil. Standard TMS is more precise when the goal is to stimulate a very specific spot on the brain’s surface. Deep TMS sacrifices some of that precision in exchange for the ability to reach deeper targets.