What is the science behind deep TMS?

A magnetic coil is placed over the skull and generates an electromagnetic field over the left prefrontal cortex. This generates action potentials to activate brain cells and with repeated sessions is hypothesized to cause longer standing changes. By increasing activity in this area of the brain, which is under-active in depression, it is believed to have anti-depressive effects. In addition, the deeper penetration given the design of the coil shape to maximize contact, it is believed to reach deeper structures in the brain involved in regulating mood. After multiple sessions, it is also believed to cause therapeutic changes to how the neurons are connected to each other.