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There is renewed interest in brain stimulation techniques as therapies for psychiatric disorders. These treatments are referred to by various names; such as, neuromodulation and somatic therapy. The methods in this type of treatment range from non-invasive therapies, such as Transcranial Magnetic Stimulation (TMS) to invasive brain surgery (deep brain stimulation).
Within the past year, several large multicenter trials have been conducted and the results are now available. These successful studies have cleared the way for US Food and Drug Administration to approve vagus nerve stimulation as a recurrent treatment for resistant depression. Further, the FDA also is currently considering approval for transcranial magnetic stimulation for the treatment of depression.
This article reviews the most important recent clinically relevant studies, and may be somewhat technical. An effort has been made to simplify or define terms that are uncommon or difficult to understand.
Several new techniques in brain stimulation as a potential therapy are working their way into clinical use. At the same time, researchers are generating new information about some of the more established brain stimulation techniques. This review highlights articles published within the recent past (2005 or 2006) covering studies using these techniques to treat psychiatric conditions, primarily depression.
The new data from brain stimulation research is explained in the recent series of studies called the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) project. This study focused on individuals with relatively poor response rates to current medication options and who fail to respond to initial treatment.
With transcranial magnetic stimulation (TMS), rapidly changing magnetic fields induce electrical current to flow within the superficial cortex. This is the outer surface of the cerebral cortex, which is the part of a person’s brain where many complex brain functions take place, such as thinking, awareness, language and consciousness. TMS is safe and without side affects that impact a person’s ability to function cognitively (the "thinking" activities). Therefore, this procedure is the least invasive of the new brain stimulation techniques, even with doses three or four times greater than those used in current clinical trials.
By far the greatest amount of research has focused on whether repeated daily TMS has antidepressant effects. Over the past 2 years a series of well-conducted clinical trials have reinforced earlier literature suggesting that TMS is an antidepressant treatment with clinically meaningful results. A group of researchers found that 30% of patients achieved remission with 3 weeks of daily TMS treatment compared to 6% for a group receiving placebo therapy. This was a well-conducted single-site trial sponsored by the National Institutes of Health. An Australian research group published two different studies, both involving stimulation of the right prefrontal cortex, which is the part of the brain responsible for how we think, interpret information and make decisions. After stimulation of the right side, some patients later respond to left prefrontal stimulation at high frequencies.
In a different study, they tested whether a 'mixed' treatment would work. Patients were treated with initial low-frequency right prefrontal TMS, followed immediately in the same session by high-frequency left prefrontal stimulation. Using this mixed treatment approach, the study showed that 44% of patients received an antidepressant response, compared with 8% who received placebo treatment. In another Australian study, researchers reported possible advantages of frequent, repetitive prefrontal treatment in relieving depression, although there was no conclusive advantage confirmed by that study.
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