TMS – Non-invasive treatment option that offers hope for patients with treatment-resistant depression
Depression is the leading cause of disability in the United States for people aged 15 to 44. Major depressive disorder affects more than 16.1 million American adults, or about 6.7%of the U.S. population age 18 and older in a given year. While major depressive disorder can develop at any age, the median age at onset is 32.5 years old. Depression is more prevalent in women than in men, with biological factors and gender roles believed to play a role.
While there are many treatment options such as antidepressant medications and psychotherapy available, these first-line treatments aren’t effective for all people suffering from depression. As many as two-thirds of patients with depression do not experience relief from the initial medication they have been prescribed. According to Harvard Medical School, at least some symptoms will remain for these individuals after two months of treatment, and each additional round of medication tried is actually less likely to be effective than the one tried previously.
What options are available for patients who do not experience symptom relief from first-line treatments for depression? For many years, electroconvulsive therapy (ECT or “shock therapy”) was considered the best option for treatment-resistant depression. ECT is still considered to be a potent and effective treatment for this condition, and it continues to be used regularly across the country.
While ECT can be an effective option for patients with treatment-resistant depression, it can also have serious negative side effects, including impairment of memory and cognition. For patients who have had an inadequate response to medications and therapy alone but do not want to risk the side effects of ECT, there is a newer treatment option, transcranial magnetic stimulation or TMS.
How Does It Work?
Transcranial magnetic stimulation (TMS) is a noninvasive procedure that uses magnetic fields to stimulate specific nerve cells in the brain to improve symptoms of depression. TMS is not typically used as a first-line treatment, but when other depression treatments haven’t proven effective. This treatment involves delivering repetitive magnetic pulses, so it’s also known as repetitive TMS or rTMS.
Unlike vagus nerve stimulation or deep brain stimulation, TMS does not require surgery or implantation of electrodes. And, unlike electroconvulsive therapy (ECT), TMS doesn’t cause seizures or require sedation with anesthesia. TMS devices operate completely outside of the body and affect central nervous system activity by applying powerful magnetic fields to specific areas of the brain that are known to be involved in depression.
During a typical TMS session, an electromagnetic coil is placed against your scalp near the patient’s forehead. The electromagnet painlessly delivers a magnetic pulse that stimulates nerve cells in the region of the brain involved in mood control and depression. It’s thought to activate areas of the brain that have decreased activity in patients with depression.
Though the biology of why TMS works isn’t completely understood, the stimulation appears to impact how the brain is functioning, and is thought to activate those regions involved with mood that have decreased activity levels, which in turn seems to ease depression symptoms.
Approximately 50% to 60% of people with depression who have failed to receive benefit from medications experience a clinically meaningful response with TMS. About one-third of these individuals experience a full remission, meaning that their symptoms subside completely. It is important to acknowledge that these results, while encouraging, are not permanent. Like most other treatments for mood disorders, there is a high recurrence rate. However, most TMS patients feel better for many months after treatment stops, with the average length of response being a little more than a year. Some will opt to come back for subsequent rounds of treatment.
What is TMS therapy like?
TMS therapy is an intensive treatment option requiring sessions that occur five days a week for several weeks. Each session may last anywhere from 20 to 50 minutes, depending on the device and clinical protocol being used.
When patients arrive, they may briefly check in with a technician or physician and then begin the stimulation process. The technician will determine the ideal stimulation intensity and anatomical target by taking advantage of a “landmark” in the brain called the motor cortex. By first targeting this part of the brain, the team can determine where best to locate the stimulation coil as it relates to that individual’s brain and how intensely it must “fire” in order to achieve adequate stimulation. Calculations are then applied to translate this data toward finding the dorsolateral prefrontal cortex, the brain target with the greatest evidence of clinical effectiveness and an area known to be involved in depression. Though one session may be enough to change the brain’s level of excitability, relief isn’t usually noticeable until the third, fourth, fifth, or even sixth week of treatment.
Generally, TMS is considered safe and well tolerated. However, it can cause some side effects. These are generally mild to moderate, typically improving shortly after an individual session and decreasing over time with additional sessions. They may include:
- Scalp discomfort at the site of stimulation
- Tingling, spasms or twitching of facial muscles
The level of stimulation can be adjusted to reduce symptoms, or an over-the-counter pain medication may be recommended prior to the procedure. Serious side effects are rare. They may include:
- Mania, particularly in people with bipolar disorder
- Hearing loss if there is inadequate ear protection during treatment
More study is needed to determine whether TMS may have any long-term side effects.
Can TMS help with other conditions?
TMS is being studied extensively across disorders and even disciplines with the hope that it will evolve into new treatments for neurological disorders, pain management, and physical rehabilitation in addition to psychiatry. There are currently large clinical trials looking at the effectiveness of TMS in conditions such as pediatric depression, bipolar disorder, obsessive-compulsive disorder, smoking cessation, and post-traumatic stress disorder. While promising avenues for research, TMS for these conditions is not yet approved and would be considered as “off-label” treatment.