There are dozens of studies that investigate the effect of tdcs on depression, but not on anxiety (generalized anxiety disorder).
I have found two randomized controlled trials, and two case studies. (studies that perform multiple sessions, there might be more of them but still much less than depression studies)
This is strange since anxiety disorders have a higher prevalence than depression, and are also quite debilitating.
What explains this relative lack of studies ? Might it be that tdcs is not very effective in this disorder so that studies that fail to find an effect don't get published ?
What would be the rationale for applying tdcs for anxiety? Just asking from curiosity.
Jesper Fabricius The same rationale as for the use of tdcs for depression. As far as a know anxiety is caused by similar neurological dysfunctions (hyperactivity of the amygdala, and hypoactivity of the DLPFC for both diseases, hyperactivity of the subgenual ACC, ventrolateral and ventromedial for depression, and hyperactivity of the insula for anxiety), and both diseases share a high rate of comorbidity (typically if you have one you also have the other).
Depression is treated (with neurostimulation, especially TMS) by stimulating the left dorsolateral prefrontal cortex (DLPFC), inhibiting the right DLPFC or inhibiting the right ventrolateral/orbitofrontal cortex.
Treating anxiety is possible with TMS, especially with inhibition of the right DLPFC (seems to work for many different types of anxiety: GAD, PTSD, Social phobia, panic), but also by inhibition of the right parietal cortex (was tested in GAD) so I was wondering why there aren't more studies that investigate the effects of tdcs on anxiety ?
Hope I answered your question.
Yes. Thank you. Sounds to me like there is no reason not to investigate this.
I found this review from last year, which included 11 articles:
Article Transcranial Direct Current Stimulation in Patients with Anx...
Here, they suggest some promising results, but suggest (as is often the case) that more RCTs are needed.
However, I also found this recent study, showing that tdcs may induce anxiety in healthy participants:
Article tDCS increases anxiety reactivity to intentional worry
I haven't gone through any of the studies, and may they stimulate different parts of the brain, but maybe it is not so straightforward?
Jesper Fabricius
Thank you for the answer you provided.
I looked up the review, and it was quite hard to interpret since there was a very high heterogeneity in montages, number of sessions, current intensity, and the disorder (MDD, anorexia nervosa, GAD, healthy people, social anxiety disorder, burn victims, mathematics anxiety), but what seems to come out of these studies is that tdcs could possibly work! (especially the bifrontal montage (anode left DLPFC, cathode right DLPFC))
Also I would be very interested to know what caused the anxiolysis in the study with burn patients: the montage used inhibited the sensory areas (parietal cortex) and reduced the pain and the anxiety. Did the reduction in anxiety come from the reduction in pain, or did it come directly from a direct anxiolytic effect of the montage (it could be possible since the sensory areas are quite connected to the insula and are known to help in the generation of emotions).
->Article Repetitive transcranial magnetic stimulation of the right pa...
->Article Repetitive transcranial magnetic stimulation of the right pa...
Concerning the study that showed that a certain tdcs montage causes anxiety: it stimulated the left DLPFC which is involved in emotional regulation. I might not have increased anxiety per say but I think it may have increased affective control, so that intentional worry increased anxiety (the key word here is intentional) more in the tdcs group. What supports this hypothesis is that the study also showed is that the tdcs group also recovered faster from the intentionally induced anxiety than the sham group, which would be consistent with higher emotional control.
What do you think about it ?
Hi Victor,
maybe these articles will help you :)
Kar, S. K., & Sarkar, S. (2016). Neuro-stimulation Techniques for the Management of Anxiety Disorders: An Update. Clinical psychopharmacology and neuroscience : the official scientific journal of the Korean College of Neuropsychopharmacology, 14(4), 330–337. https://doi.org/10.9758/cpn.2016.14.4.330
de Lima, A. L., Braga, F. M. A., da Costa, R. M. M., Gomes, E. P., Brunoni, A. R., & Pegado, R. (2019). Transcranial direct current stimulation for the treatment of generalized anxiety disorder: a randomized clinical trial. Journal of affective disorders, 259, 31-37.
Stein, D. J., Medeiros, L. F., Caumo, W., & Torres, I. L. (2020). Transcranial direct current stimulation in patients with anxiety: current perspectives. Neuropsychiatric Disease and Treatment, 16, 161.
Clarke, P. J., Sprlyan, B. F., Hirsch, C. R., Meeten, F., & Notebaert, L. (2020). tDCS increases anxiety reactivity to intentional worry. Journal of psychiatric research, 120, 34-39.
Heeren, A., Billieux, J., Philippot, P., De Raedt, R., Baeken, C., de Timary, P., ... & Vanderhasselt, M. A. (2017). Impact of transcranial direct current stimulation on attentional bias for threat: a proof-of-concept study among individuals with social anxiety disorder. Social cognitive and affective neuroscience, 12(2), 251-260.
Kind regards
Pavla
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