Standard TMS and deep TMS use the same core principle, magnetic pulses to stimulate brain cells, but they differ in how deep those pulses reach and which brain regions they can target. Standard TMS penetrates about 1 to 1.5 centimeters into the brain, reaching only the outer cortical surface. Deep TMS reaches further into subcortical structures, thanks to a differently shaped coil that produces a broader magnetic field.
How the Coils Differ
The key hardware difference is the coil placed against your head. Standard TMS typically uses a figure-8 coil: two flat loops of wire positioned side by side. Where the loops meet, their magnetic fields overlap and create a focused pulse. This design is precise but shallow. The electric field drops off rapidly as it moves deeper into brain tissue.
Deep TMS uses what’s called an H-coil, developed by a company called BrainsWay. Several variations exist (H1, H4, H7), each shaped to target different brain regions. These coils have a more complex, three-dimensional winding pattern that distributes the magnetic field over a wider area, allowing it to maintain enough strength to stimulate neurons well below the cortical surface. The tradeoff is less precision: deep TMS activates a larger volume of brain tissue rather than a tight, focused spot.
Depth and Brain Regions Targeted
Standard TMS with a figure-8 coil generates a focused electric field that reaches about 1 to 1.5 centimeters deep. That’s enough to stimulate the outer layer of the brain’s cortex, and it works well for surface-level targets like the dorsolateral prefrontal cortex, a region involved in mood regulation.
Deep TMS can push meaningful stimulation into subcortical areas that standard coils simply can’t reach. For example, the H7 coil is designed to target the medial prefrontal cortex and the anterior cingulate cortex, a structure buried in the middle of the brain that plays a central role in compulsive behaviors. In modeling studies, the H7 coil stimulates above therapeutic threshold across several regions simultaneously, including the orbitofrontal cortex, dorsolateral prefrontal cortex, and pre-supplementary motor area.
This ability to reach deeper structures is the entire reason deep TMS was developed. Conditions like OCD involve circuits that loop through brain areas too deep for a standard figure-8 coil to activate effectively.
FDA-Cleared Uses
Standard TMS was first cleared by the FDA in 2008 for major depressive disorder and later expanded to include migraine-related pain in 2013. Multiple device manufacturers offer figure-8 coil systems for depression treatment.
Deep TMS has its own set of clearances. The H1 coil is cleared for major depression. The H7 coil received FDA clearance in August 2018 specifically for OCD treatment. And the H4 coil, which targets the bilateral insula and prefrontal cortices, is cleared for smoking cessation. That smoking indication is unique to deep TMS; no standard TMS device has it.
How Treatment Sessions Compare
For depression, both standard TMS and deep TMS follow a similar overall course: sessions are typically delivered several times per week over about six weeks. A standard TMS session for depression commonly lasts 15 to 30 minutes, depending on the protocol used. Studies comparing 15-minute and 30-minute standard TMS sessions for depression have found no difference in outcomes.
The FDA-approved deep TMS protocol for OCD involves daily sessions over six weeks, with each session preceded by a brief provocation exercise designed to activate the OCD circuit before stimulation. For the smoking cessation indication, the treatment course is shorter, around three weeks. In both cases, patients sit in a chair with a padded helmet-like device placed over the head. The sensation is a tapping or knocking feeling on the scalp during pulses.
How Effective Is Each One?
For depression, the evidence suggests both approaches work, and neither is dramatically superior. A systematic review that included randomized controlled trials found similar efficacy and safety for both techniques in treatment-resistant depression, with no significant differences in remission rates overall.
One 2019 randomized trial did show a numeric advantage for the deep TMS H1 coil: after 20 sessions, 60% of patients in the deep TMS group achieved remission compared to 43% in the standard TMS group and 11% in a control group. The average reduction in depression scores was 59% with deep TMS versus 41% with standard TMS. But across the small number of head-to-head studies that exist, the review authors concluded the difference in remission rates was not statistically significant. More direct comparisons are needed before anyone can confidently say one is better than the other for depression.
For OCD, deep TMS has the stronger evidence base simply because it’s the modality that was tested in the pivotal trials. The H7 coil’s ability to reach the anterior cingulate cortex, a key node in the obsessive-compulsive circuit, gives it a mechanistic rationale that standard TMS lacks for this condition. Brain chemistry studies in OCD patients have confirmed that deep TMS with the H7 coil produces measurable changes in the anterior cingulate cortex, indicating direct stimulation of that region.
Safety and Side Effects
Both standard and deep TMS are considered safe. The most common side effect for both is scalp discomfort or a headache during or after treatment, which tends to diminish over the first few sessions.
The most serious risk is seizure, but it is rare with either technology. Overall TMS-related seizure risk is below 1%. For standard figure-8 coils, one estimate puts it at roughly 0.08 per 1,000 sessions. For H-coils used in deep TMS, the reported rate is somewhat higher at about 0.43 per 1,000 sessions, or roughly 0.087% based on a review of BrainsWay H1 coil data. The slightly elevated rate with deep TMS likely reflects the larger volume of brain tissue being stimulated. In practice, both rates are very low, and seizures that do occur during TMS are typically brief and self-limiting.
People with a history of epilepsy, metallic implants near the head, or certain other neurological conditions are generally not candidates for either form of TMS.
Which One Is Right for You
If you’re being treated for depression, both standard TMS and deep TMS are reasonable options with similar overall outcomes. Availability and insurance coverage may be the deciding factors, since standard TMS devices are more widely distributed across clinics. If you’re seeking treatment for OCD, deep TMS with the H7 coil is the only FDA-cleared TMS option for that condition. The same applies to smoking cessation, where the H4 deep TMS coil holds the only clearance.
Cost is comparable for both, though deep TMS sessions can sometimes run slightly higher because of the specialized equipment. Most clinics that offer TMS will discuss which coil type they use and why it’s appropriate for your specific condition.