Is TMS (transcranial magnetic stimulation) effective for seasonal depression or Bipolar II disorder?
Transcranial magnetic stimulation (TMS) refers to the use of magnetic fields to stimulate the brain. The magnetic fields induce small electrical currents in the brain, which can activate neuronal circuits. Repeatedly activating functional networks in the brain can alter the functioning of those networks in ways that might be therapeutic. The therapeutic potential of TMS is under study.
TMS is under study for the treatment of a range of psychiatric and neurological disorders, including depression, schizophrenia, anxiety disorders, Parkinson’s Disease, and stroke, just to name a few. TMS is not presently approved by the Food and Drug Administration (FDA), therefore TMS is considered experimental.
Several studies have examined the potential use of TMS for depression, with some encouraging results. Several meta-analyses have provided supporting evidence for a modest antidepressant effect of TMS applied to the left dorsolateral prefrontal cortex when applied daily for 4 to 6 weeks. A recently completed randomized controlled trial of over 300 patients with unipolar depression found a significantly higher response rate with active TMS than with a placebo condition (sham TMS) (O’Reardon et al. 2007).
Most of the studies on TMS in psychiatric disorders have focused on depression, and most of those have focused on unipolar depression. Relatively little is known about the potential of TMS in the treatment of seasonal affective disorder, or bipolar disorder. A search of Medline reveals no papers on TMS in the treatment of seasonal affective disorder. It appears that the potential of TMS in the study or treatment of seasonal affective disorder is unexplored as of this time. The application of TMS in depression was predicated on a theory regarding the neurobiology of depression that implicated a network of brain regions. One of these regions, the dorsolateral prefrontal cortex, has been reported to be under-active in depression and so TMS was applied in an attempt to correct that abnormality. The application of TMS to other disorders, such as seasonal affective disorder, would naturally start with a model for the neurobiology of the disorder that could serve as a map for how to apply TMS. It is not clear that the targets would necessarily be the same for depression with and without a seasonal pattern. This may be a fruitful area for future research.
There are very few studies on TMS in the treatment of bipolar disorder. Nahas et al. (2003) reported a randomized controlled trial of 23 bipolar patients treated with TMS to the left dorsolateral prefrontal cortex (DLPFC). Nine of these patients were bipolar II. While TMS was found to be relatively safe, they failed to find significant benefit from TMS. Later, the same group (Li et al (2004)) reported on the open-label treatment of 7 bipolar patients who responded to an acute course of TMS, 3 of whom sustained remission with weekly TMS given over a year. This demonstrates that patients can respond very differently in blinded versus open trials, and argues for the need for larger blinded trials to resolve the issue of whether TMS can be helpful in treating depression in bipolar disorder.
It is important to note that, as seen with antidepressant medications, there are reports that TMS can induce mania in bipolar patients. On the other hand, TMS has been studied in the treatment of mania when applied to the right DLPFC, based on the theory that the laterality of mania would be opposite to that of depression. However, while a few open reports suggested there was benefit, a sham-controlled trial found none (Kaptsan et al. 2003).
In summary, more work is needed before conclusions can be drawn about the therapeutic utility of TMS in seasonal affective disorder and bipolar II disorder, and well-controlled blinded trials will be needed to address these questions.
For more information about TMS programs at Columbia, see the following links:
Kaptsan A, Yaroslavsky Y, Applebaum J, Belmaker RH, Grisaru N. Right prefrontal TMS versus sham treatment of mania: a controlled study. Bipolar Disord. 2003 Feb;5(1):36-9.
Li X, Nahas Z, Anderson B, Kozel FA, George MS. Can left prefrontal rTMS be used as a maintenance treatment for bipolar depression? Depress Anxiety. 2004;20(2):98-100.
Nahas Z, Kozel FA, Li X, Anderson B, George MS. Left prefrontal transcranial magnetic stimulation (TMS) treatment of depression in bipolar affective disorder: a pilot study of acute safety and efficacy. Bipolar Disord. 2003 Feb;5(1):40-7.
O'Reardon JP, Solvason HB, Janicak PG, Sampson S, Isenberg KE, Nahas Z, McDonald WM, Avery D, Fitzgerald PB, Loo C, Demitrack MA, George MS, Sackeim HA. Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biol Psychiatry. 2007 Dec 1;62(11):1208-16.