How does it work?
Like many other antidepressant treatments that are available in clinical practice, the exact mechanism by which rTMS produces relief from depression is still unknown.
At a physiological level the effects of rTMS are frequently reported to be due to changes in synaptic plasticity (the ability of nerve cells in the brain to connect and disconnect). Synaptic plasticity has been widely studied as a mechanism to explain learning and memory (Luscher and Malenka 2012). Studies indicate that large scale brain networks are disconnected in patients with depression, and the degree of the change in their connectivity can predict the severity of depression (Salomons et al. 2014). Repetitive stimulation in areas of these networks can result in increased connection in the brain and reduction or elimination of depressive symptoms. Research suggests that rTMS results in changes in regional brain blood flow and metabolism, and applying rTMS at specific areas of the brain can enhance this region’s connectivity with other regions that are crucial for regulating emotional processing (Kito et al. 2008).
The picture above shows the blood flow in a non depressed brain *uniform on both sides and lots of yellow areas showing good blood flow, in contrast the brain on the left show large blue areas where blood flow, and therefore brain activity, is low.
It has long been known that stimulating nerves at more than 5 times per second causes the nerves to connect together, this was remarked on by Hebbs who discovered the phenomenon as nerves that fire together wire together. Similarly if nerves are stimulated once a second they disconnect, this phenomenon is used to treat anxiety with rTMS.
In 2008, rTMS was approved by the United States Food and Drug Administration (FDA) for treatment of patients suffering from depression who have not achieved satisfactory improvement from one antidepressant medication at or above the minimal effective dose and duration in the current episode. In England, the National Institute for Health and Care Excellence (NICE 20015) issued guidance for the use of rTMS recommending it as a treatment for depression. The Royal College of Psychiatrists have issued a statement on rTMS recommending it as a treatment for depression, Prof Alex was part of the steering committee of the Royal College of Psychiatrists which wrote the College standards for rTMS.
