How Does Transcranial Magnetic Stimulation Help Treat Depression?

What you need to know

• Transcranial magnetic stimulation (TMS) is a non-invasive treatment that uses magnetic fields to stimulate specific brain areas involved in mood regulation.
• TMS is approved for treating depression that hasn’t responded to other treatments, with about 30-40% of patients seeing improvement.
• It is generally safe with minimal side effects compared to other depression treatments like medication or electroconvulsive therapy.

What is transcranial magnetic stimulation?

Transcranial magnetic stimulation, or TMS, is a non-invasive method of stimulating the brain using magnetic fields. It works by placing an electromagnetic coil against the scalp, which creates a magnetic field that passes through the skull and induces small electrical currents in targeted brain regions. This can temporarily increase or decrease brain activity in those areas.

TMS was first developed in 1985 and has since become an important tool in neuroscience research as well as a treatment for various neurological and psychiatric conditions. For depression specifically, TMS received approval from the US Food and Drug Administration (FDA) in 2008 as a treatment for major depressive disorder that hasn’t responded to at least one antidepressant medication.

How does TMS work for depression?

Depression is thought to involve abnormal activity and connectivity in brain networks that regulate mood. One key region is the dorsolateral prefrontal cortex (DLPFC), an area towards the front and side of the brain involved in emotional processing and regulation.

In people with depression, studies have found reduced activity in the left DLPFC. TMS treatment for depression typically involves stimulating this region to increase its activity. The most common protocol uses high-frequency pulses (usually 10 Hz) applied to the left DLPFC for about 37 minutes a day, 5 days a week, for 4-6 weeks.

By repeatedly activating the DLPFC and its connections to other mood-related brain regions, TMS is thought to gradually strengthen and rebalance the brain circuits involved in mood regulation. This can lead to improvements in depression symptoms over the course of treatment.

How effective is TMS for depression?

TMS has been shown to be moderately effective for treating depression, particularly in cases that haven’t responded well to antidepressant medications. Studies estimate that about 30-40% of patients with treatment-resistant depression will respond to TMS therapy.

Some factors that may predict a better response to TMS include:

• Younger age (under 65)
• Shorter duration of current depressive episode
• Fewer failed medication trials
• No psychotic symptoms
• Higher intensity of stimulation used
• More total TMS sessions received

While not as rapidly effective as treatments like electroconvulsive therapy (ECT), TMS has the advantage of being very well-tolerated with minimal side effects. It also doesn’t require anesthesia or cause cognitive side effects like memory loss.

For patients who do respond, TMS can lead to significant improvements in depression symptoms and quality of life. Some may achieve full remission, while others may have a partial response that enhances the effects of other treatments like medication.

Is TMS safe?

TMS is generally considered a very safe procedure with minimal risk of serious side effects. The most common side effects are mild and include:

• Headache
• Scalp discomfort at the stimulation site
• Lightheadedness
• Tingling or twitching of facial muscles

These effects are usually temporary and resolve soon after each session. More serious risks are rare but can include:

• Seizures (estimated risk less than 1 in 30,000 sessions)
• Hearing problems due to the loud clicking noise of the TMS coil
• Mania in patients with bipolar disorder

To minimize risks, patients undergo screening before TMS to check for contraindications like metal implants in the head, history of seizures, or certain medications. Proper ear protection is also used during treatment.

Overall, TMS has a much better safety profile than other treatments for resistant depression like ECT. It avoids the need for anesthesia and the cognitive side effects associated with ECT.

How does TMS compare to other depression treatments?

When compared to antidepressant medications, TMS has shown similar or superior efficacy for treatment-resistant depression, with a much lower risk of side effects. Unlike medications which affect the whole body, TMS can target specific brain regions involved in depression.

Compared to ECT, TMS is somewhat less effective overall, especially for severe depression with psychotic features. However, TMS is much better tolerated, doesn’t require anesthesia, and avoids the memory loss and cognitive impairment that can occur with ECT. For this reason, TMS is often tried before ECT in patients who haven’t responded to medications.

Some key comparisons:

• Antidepressants: TMS has fewer systemic side effects, may work faster
• ECT: TMS is less effective but has far fewer side effects and risks
• Psychotherapy: TMS works through a different mechanism, may be combined
• Ketamine: TMS works more gradually but effects may last longer

For many patients with treatment-resistant depression, TMS offers a middle ground between medications and more intensive treatments like ECT. It provides a non-invasive option with minimal side effects that can be effective when other treatments have failed.

Conclusions

• TMS is a safe, non-invasive treatment option for depression that uses magnetic fields to stimulate specific brain regions.
• It is moderately effective for treatment-resistant depression, with about 30-40% of patients responding.
• TMS has minimal side effects compared to other treatments, making it a good option to try before more intensive therapies.
• While not a cure-all, TMS expands the range of available treatments for depression and may help many patients achieve remission or better quality of life.