TMS and Anxiety
The potential of TMS in the research of anxiety disorders includes determining the pathophysiology, improving our understanding of physiological endophenotypes and comprehension of neuroanatomical networks. Increased understanding in these areas may lead to improved treatment options and, in turn, mediation of symptoms (George & Belmaker 2007).
Relatively few studies have investigated TMS in axienty to date; however those so far have been encouraging. A study in 2008 (Bystritsky et al) used fMRI-guided rTMS in the treatment of generalised anxiety disorder (GAD) to evaluate whether it is effective in reducing symptoms. fMRI was first used to determine the most active location in the prefrontal cortex of ten participants with a DSM-IV diagnosis of GAD. Ten participants received rTMS over the course of 3 weeks, stereotactically directed to the previously determined prefrontal location. The primary efficacy measures were the Hamilton Rating Scale for Anxiety (HAM-A) and the Clinical Global Impressions-Improvement of Illness (CGI-I) scale. Overall, rTMS was associated with significant decreases in HAM-A scores, indicative of clinical improvement in GAD symptoms. At endpoint, 60% of the participants showed reductions of 50% or more on the HAM-A, and a CGI-I score of 1 or 2; those subjects also had an endpoint HAM-A score < 8, therefore meeting criteria for remission.
Though this study had a small sample size, these results have been correoborated by the findings of a systematic review: Zwanzger et al (2009) confirm that there is evidence for anxiolytic action of rTMS both from preclinical trials and studies in humans. Based on the idea of interhemispheric imbalance and/or deficits in cortico-limbic control as a model for human anxiety, inhibitory rTMS of the prefrontal cortex has been shown to exert beneficial effects in a number of studies.
References
- Bystritsky et al., J Clin Psychiatry, 2008.
- George & Belmaker, Transcranial Magnetic Stimulation in Clinical Psychiatry, 2007.
- Zwanzger et al., Journal of Neural Transmission, 2009.
