Repetitive transcranial magnetic stimulation (rTMS), defined as the administration of a series of magnetic stimuli to the brain for the purpose of altering brain function, is an experimental medical intervention. rTMS currently is used to probe various aspects of brain function in the context of research studies approved by local ethics committees. rTMS also is under investigation as a potential treatment for various neurologic and psychiatric disorders. In light of the growing interest in using rTMS in a variety of experimental and therapeutic settings, the International Society for Transcranial Stimulation has recognized the need to formulate a consensus statement to assist the field in developing guidelines for its safe application. Whether the intended use is experimental or therapeutic, certain principles regarding the safety of rTMS apply. This statement is not aimed at guiding the therapeutic use of rTMS in any given condition or its application in any research paradigm, but rather is meant to apply broadly wherever rTMS is used.

rTMS has significant risks, most importantly that of producing epileptic seizures. The degree of risk varies with the dosing parameters and individual subject factors. Therefore, rTMS should be administered only under a licensed physician's orders (ie, by prescription or through some other mechanism that makes a physician directly responsible for its administration to the individual patient or research subject). Because rTMS has potential behavior-changing effects, undesirable side effects, and therapeutic impact, careful assessment of the risk and appropriateness of rTMS in each clinical or scientific context is critical and can only be made by, or in consultation with, a physician knowledgeable and experienced in the use of rTMS and fully trained in neurology, psychiatry, or another appropriate specialty.

Brain stimulation methods in the treatment of affective disorder are electroconvulsive therapy (ECT), transcranial magnetic stimulation (TMS), vagus nerve stimulation (VNS), and deep brain stimulation (DBS). Clinically, ECT is considered the strongest remedy in the treatment of severe depression, especially depression with psychotic features, and in the elderly. TMS, despite positive reports, is somewhat more controversial. VNS has, so far, only been used in treatment-resistant depression with limited results. DBS may be of potential use in rare cases of treatment-resistant cases of affective disorder. This article highlights the similarities and differences between the four stimulation methods. The main difference is the seizures necessary in ECT. A stronger involvement of the hippocampus following experimental seizures compared with effects in that region induced by TMS and VNS might explain the consistent findings of the superiority of ECT in the most severe cases of affective disorder.

Transcranial magnetic stimulation (TMS) is unique among the current brain stimulation techniques because it is relatively non-invasive. TMS markedly differs from vagus nerve stimulation, deep brain stimulation and magnetic seizure therapy, all of which require either an implanted prosthesis or general anesthesia, or both. Since its rebirth in its modern form in 1985, TMS has already shown potential usefulness in at least three important domains—as a basic neuroscience research instrument, as a potential clinical diagnostic tool, and as a therapy for several different neuropsychiatric conditions. The TMS scientific literature has now expanded beyond what a single summary article can adequately cover. This review highlights several new developments in combining TMS with functional brain imaging, using TMS as a psychiatric therapy, potentially using TMS to enhance performance, and finally recent advances in the core technology of TMS. TMS' ability to non-invasively and focally stimulate the brain of an awake human is proving to be a most important development for neuroscience in general, and neuropsychiatry in particular.

Vagus nerve stimulation (VNS) in humans generally refers to stimulation of the left vagus nerve at the cervical level. VNS is an established treatment largely devoid of severe side effects for medically refractory partial-onset seizures and has been used in more than 16,000 patients. Over the past 5 years, applications in other neuropsychiatric disorders have been investigated, with a special emphasis on depression. Recent data from an open-label, multi-center pilot study involving 60 patients suggest a potential clinical usefulness in the acute and maintenance treatment of drug-resistant depressive disorder. The perspective of VNS as a long-term treatment with the advantage of assured compliance makes it an interesting technique to potentially treat drug-resistant depression. However, definite therapeutic effects of clinical significance remain to be confirmed in large placebo-controlled trials. Results of clinical pilot studies involving patients suffering from obesity and Alzheimer's disease indicate that VNS might induce weight loss and improve cognition. Besides its clinical usefulness, VNS can be used as a research tool, allowing neuro-physiologic investigations of the parasympathetic system and its interactions with other parts of the central nervous system.

Deep brain stimulation (DBS) is established as a therapy for movement disorders, and it is an investigational treatment in other neurologic conditions. DBS precisely targets neuroanatomical targets deep within the brain that are proposed to be centrally involved in the pathophysiology of some neuropsychiatric illnesses. DBS is nonablative, offering the advantages of reversibility and adjustability. This might permit therapeutic effectiveness to be enhanced or side effects to be minimized. Preclinical and clinical studies have shown effects of DBS locally, at the stimulation target, and at a distance, via actions on fibers of passage or across synapses. Although its mechanisms of action are not fully elucidated, several effects have been proposed to underlie the therapeutic effects of DBS in movement disorders, and potentially in other conditions as well. The mechanisms of action of DBS are the focus of active investigation in a number of clinical and preclinical laboratories. As in severe movement disorders, DBS may offer a degree of hope for patients with intractable neuropsychiatric illness. It is already clear that research intended to realize this potential will require a very considerable commitment of resources, energy, and time across disciplines including psychiatry, neurosurgery, neurology, neuropsychology, bioengineering, and bioethics. These investigations should proceed cautiously.

New findings regarding the mechanisms of action of electroconvulsive therapy (ECT) have led to novel developments in treatment technique to further improve this highly effective treatment for major depression. These new approaches include novel electrode placements, optimization of electrical stimulus parameters, and new methods for inducing more targeted seizures (eg, magnetic seizure therapy [MST]). MST is the use of transcranial magnetic stimulation to induce a seizure. Magnetic fields pass through tissue unimpeded, providing more control over the site and extent of stimulation than can be achieved with ECT. This enhanced control represents a means of focusing the treatment on target cortical structures thought to be essential to antidepressant response and reducing spread to medial temporal regions implicated in the cognitive side effects of ECT. MST is at an early stage of development. Preliminary results suggest that MST may have some advantages over ECT in terms of subjective side effects and acute cognitive functioning. Studies designed to address the antidepressant efficacy of MST are underway. As with all attempts to improve convulsive therapy technique, the clinical value of MST will need to be established through controlled clinical trials. This article reviews the experience to date with MST, and places this work in the broader context of other means of optimizing convulsive therapy in the treatment of depression.