Transcranial Magnetic Stimulation (TMS) for Depression: Does It Work?

What Is Transcranial Magnetic Stimulation (TMS)?

Transcranial magnetic stimulation (TMS) is a relatively safe, non-invasive procedure in which a coil that carries an electric current is placed against the head, producing a magnetic field that penetrates the scalp, skull, cerebrospinal fluid (CSF) and stimulates neurons in the brain to activate (i.e., fire). Activating groups of neurons in specific brain areas is believed to stimulate underperforming brain regions that underlie mental health disorders.

Despite being generally well-tolerated and FDA-approved to treat major depressive disorder (MDD), it is usually only recommended by providers and covered by insurance after traditional treatment methods (e.g., medication, psychotherapy, etc.) have been shown to be ineffective. The use of magnets and electric current preclude some people from receiving this treatment — e.g., those with epilepsy or pacemakers — but TMS providers can help determine if you meet the criteria.

Different Types of TMS

The different types of TMS have to do with varying magnet strength, or ways to apply the magnetic field.¹¹

• Magnet strength: The unit for measuring magnet strength is called the tesla (T). Most TMS magnets generate a magnetic field with a strength of 1.5T to 2T, which is similar to an MRI scanner, though the TMS magnet is much smaller.
• Pulse frequency: Each time the magnetic field turns on and off is a pulse. TMS typically uses pulse rates from 1Hz (one pulse per second) up to 10Hz.
• Pulse patterns: Using burst patterns in TMS may speed up treatment, making it up to six times faster than other treatment methods.
• Magnetic coil type and stimulation target: Different kinds of magnetic coils can target different brain structures. For example, deep TMS (dTMS) targets deeper brain structures and may be effective in treating OCD.

Does TMS Work for Depression?

Traditional treatment methods like psychotherapy or medication are not always effective for relieving symptoms of depression. For individuals with treatment-resistant depression, TMS was cleared by the FDA as a treatment in 2013.³ By sending pulses of magnetic current to an area of the brain called the left prefrontal cortex, TMS increases activity in neural circuits that are dysregulated in depressed individuals.

The Advantages of TMS for Depression

TMS is an FDA-approved treatment for depression, and has been shown to be effective in reducing symptoms of treatment-resistant depression.¹²

Advantages of TMS for depression include:

• Noninvasive: TMS is completely noninvasive, stimulating the brain from outside of the body.
• Effective:  Studies show that more than half of people who tried other treatments for depression without success experience a clinically meaningful response with TMS.¹³
• Safe: TMS is considered a safe treatment for depression, has few side effects, and is approved by the FDA.
• Targeted: TMS specifically targets areas of the brain that involve mood regulation.
• Personalized: Individual brain connectivity patterns are taken into consideration in order to determine the best sites for stimulation through TMS, allowing practitioners to personalize treatment to each person for greater efficacy.
• Can work well in combination with other treatments: TMS can work alongside psychotherapy, medication, lifestyle changes, and alternative treatments like acupuncture in order to effectively support a person struggling with depression.

Common Side Effects of TMS for Depression

Headaches are the most common side effect of a TMS session but tend to alleviate with successive treatments and are usually treatable with over-the-counter medication. Despite this side effect, TMS  has also been found to be helpful in treating migraine pain.

Additional potential side effects of a TMS session include:

• Seizures (the risk is similar to seizure side effects from medication; one study estimated that 2 in 10,000 patients may experience a seizure²
• Dizziness
• Syncope (passing out)
• Tingling sensations
• Scalp discomfort and mild pain
• Muscle twitching
• Fatigue
• Anxiety
• Insomnia
• Jaw pain
• Back and neck pain
• Dislodging or heating of metal located in head or neck (but having ferrous metal in the body would most likely disqualify one from receiving treatment)
• Damage to implanted device (e.g., pacemaker)
• Hearing loss (although earplugs are worn to prevent this)
• Manic episodes (in individuals with bipolar disorder)

How Effective Is TMS for Depression?

TMS has been extensively studied clinically for the treatment of depressive symptoms. It is most effective when used in conjunction with antidepressant medication (in the case of MDD) or psychotherapy, suggesting a synergistic effect when coupled with other treatments, even if they weren’t effective individually.^4,5

The success rate of TMS is promising. Research shows that response rates to TMS range from 50 to 55%, and the rate of remission ranges between 30 to 35% in patients with depression.¹⁴

As with medication and therapy, the effects of TMS are not felt immediately. Symptom relief can take several weeks of treatment and has only been documented to last for a few months, although it remains possible that the effects last longer.

TMS Vs. dTMS for Depression

Research suggests that when used together with medication, deep TMS (dTMS) is more effective than conventional TMS. Deep TMS has a 60% symptom remission, whereas conventional TMS has a 43% symptom remission.^6,7 Remission rates for dTMS are similar to those reported for therapeutic psychedelic intervention (58% remission rate for psilocybin treatment), but are more time-intensive (weeks to months of daily TMS sessions vs. 2-3 doses of psilocybin).^8,9

Who Should Avoid TMS for Depression?

Before receiving TMS, individuals must be screened to ensure eligibility and safety. The healthcare professional will ask a series of questions prior to treatment, and in some cases, clearance from one’s medical team is required to determine if TMS is a viable option.

Populations who should avoid TMS treatment for depression include those who:

• Are pregnant or nursing
• Have implanted medical and electronic devices (stents, stimulators, pacemakers, cardioverter defibrillators, cochlear implants, etc.)
• Have any other metal device or object in the body (bullet fragments, metal plate, etc.), although amalgam dental fillings are okay. Many current metal implants are non-ferrous (e.g., titanium) and may be safe as well.
• Have a history of seizures/epilepsy
• Have another medical condition associated with a risk for seizures
• Have brain damage from illness or injury
• Experience frequent or severe headaches (though sometimes dTMS can paradoxically be a treatment for migraine pain)
• Do not meet DSM criteria to meet the FDA or ICD indications for the CE Marked (Europe) approved condition to be treated
• Have not already tried and shown resistance to traditional treatments

What to Expect From TMS for Depression

TMS treatment for depression is an intensive daily treatment that can be time-consuming and requires commitment. The treatment course may vary slightly, depending on the symptom(s) being treated. Still, it typically consists of daily, 20-minute sessions, five days per week, for up to six weeks, followed by a taper period of fewer weekly sessions for three weeks.

Here are some things to expect during TMS treatment for depression:

• Location: TMS usually takes place in an outpatient office or clinic setting, though it can be a hospital setting, especially for clinical research trials.
• Evaluation: Before treatment, you will be asked a series of questions to help the clinicians determine if TMS is a safe and effective treatment for you.
• Procedure preparation: This procedure is non-invasive and does not require any surgery, needles, or other penetration of skin, nor anesthesia. You will be awake for the entire procedure. Measurements of your head may be taken to help identify your personal target location for stimulation.
• Setting: During a treatment session, you will be seated in a comfortable chair. As the procedure involves a magnetic field, you will not be able to bring any ferrous metal (jewelry, keys, glasses) into the room. At this point, earplugs will be placed since the treatment can be loud.
• Device placement: The TMS coil in the form of a cushioned helmet or panel will be placed against your scalp at a location specified to treat your symptom(s). Once the coil is placed, it is crucial that you stay still, but you may be allowed to talk or read as long as your head doesn’t move.
• Personalized target: As brain shape and size vary between individuals, there are several methods that the clinician may use to determine the target to stimulate. Some methods require head measurements, while others require prior neuroimaging.
• Determining intensity: The clinician will stimulate your motor cortex to identify your “motor threshold” – i.e., the pulse intensity that will cause your hand to contract. Your treatment intensity will be relative to this value (usually 80% to 120% depending on the condition). This threshold can change with sleep deprivation, medication, alcohol or drug use, so it is important that you notify the clinician before a session if there’s been a change to any of these factors between sessions.¹⁰
• Sensations: As the treatment begins, you will hear loud, repetitive noises despite wearing earplugs. You may experience tapping or clicking sensations against your scalp. Some individuals have described this as a light, repetitive tapping or knocking on the head.
• Daily activity: You can resume your daily activities immediately after each session, and generally, there is no recovery period or restrictions on driving or operating machinery unless a seizure occurs as a side effect.
• Subsequent sessions: The stimulation parameters are determined during the first session and need not be repeated every session unless there have been changes to sleep or substance use (including medications) that may impact the motor threshold.¹⁰ Subsequent daily sessions are usually briefer than the first session.
• Monitoring effects of treatment: There is variation in how different people respond to treatment. With feedback, parameters may be adjusted, but generally, improvement is not felt for the first few weeks of treatment. After the final session, symptom relief may last anywhere from weeks to months, with some reporting lasting effects for one year. In some cases, brush-up sessions may be recommended when treatment effects wane.

How Many TMS Sessions Does Someone With Depression Need?

Daily TMS treatments, five days per week, for four to six weeks, amounting to 30 treatments, is the FDA-approved protocol for this treatment.¹⁵ While most studies indicate that patients who show improvement with TMS do so within four to six weeks of treatment, implementing a shorter or longer course of treatment can be beneficial in certain circumstances. For example, someone with treatment resistant depression who has not shown any benefit after six weeks might continue treatment for a longer period in hopes of achieving some relief from their symptoms.¹⁵

How Long Do the Effects of TMS Last?

The effects of TMS typically last from six months to a year, or more, after the four to six week treatment protocol.¹⁶ Some patients might require occasional maintenance treatments in order to continue experiencing symptom relief. The effects of TMS vary from person to person, and it is important to work with your physician to determine the best treatment plan for you.

How to Find TMS for Depression

The main company providing dTMS devices (which have shown greater efficacy than conventional TMS) is BrainsWay, and they offer a directory for finding a dTMS provider near you. You may want to consult a psychiatrist to determine if TMS is a viable option for you. If you have trouble finding a psychiatrist near you, there are online psychiatry services or ask your healthcare provider. Lastly, you can search a clinical trial database for research studies to participate in if you find that clinical options for your condition are not available.