More than 264 million people suffer from depression, according to the World Health Organization. And for some of them, traditional pharmaceuticals and psychotherapy don’t work. A procedure called transcranial magnetic stimulation (TMS) could provide relief for these patients.

TMS is a noninvasive, FDA-approved procedure that uses a magnetic field to stimulate nerve cells in the brain. TMS is typically used when other depression treatments haven't been effective.

During a TMS session, an electromagnetic coil about the size of a ping pong paddle is placed against your scalp near your forehead. The electromagnet painlessly delivers a magnetic pulse that stimulates nerve cells in the regions of your brain involved in mood regulation and depression, such as the prefrontal cortex. It's thought to activate regions of the brain that have decreased activity during depression. There’s no anesthesia, and you’re awake for the whole procedure.

So what does it feel like? Your brain doesn’t sense the stimulation, but your scalp does. You might feel a tiny tapping on your head and hear a clicking noise, which is the coil vibrating. Sessions last from five to 40 minutes, and there’s no downtime after a treatment and you can drive yourself home. Side effects, if experienced, tend to be mild and improve shortly after a session, and decrease over time with additional sessions. These can include headaches, twitching of facial muscles and scalp discomfort. Serious side effects, such as seizures, are very rare.

Typically, treatments are given Monday through Friday for four to six weeks. TMS tends to be quite effective, with 50% to 60% of patients responding. If TMS works for someone, their depression symptoms improve or can even go away completely. Symptom relief may require a few weeks of treatment. After they improve, many patients continue with maintenance treatment to keep depression at bay.

TMS sessions are prescribed by a physician. If you’re pregnant, have any type of non-removable metal in your head (with the exception of braces or dental fillings) or facial tattoos with metallic or magnetic-sensitive ink, you shouldn’t have TMS therapy.