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Transcranial direct current stimulation (tDCS) was associated with significant elevations in anxiety after a worry induction task, according to study data published in the Journal of Psychiatric Research. The study revealed some potential concerns for a promising neuromodulatory intervention for mood disorders.
Patrick J.F. Clarke, PhD, and colleagues designed a study to capture the effect of tDCS on the cognitive and emotional effects of worry. Healthy individuals without a history of psychiatric illness were recruited from Curtin University’s School of Psychology in Perth, Australia. At baseline, general emotional distress was measured using the 21-item Depression, Anxiety, and Stress scale, and anxiety was assessed with the State Trait Anxiety Inventory 6 times.
Participants received either active or sham anodal tDCS to the left dorsolateral prefrontal cortex. While receiving tDCS, participants assigned to the mindful-focus condition engaged in a 14-minute guided body-scan meditation. Participants in the mind-wandering control condition were instead instructed to allow their mind to wander for a 14-minute period during tDCS. After the tasks, frequency of intrusive thoughts was assessed before and after a worry induction procedure, in which participants were asked to identify a source of anxiety in their lives. A mixed model analysis of variance was conducted to assess the effect of tDCS and the mindful-focus condition on thought intrusions and state anxiety.
A total of 97 patients (75 women) were enrolled, with 50 receiving active tDCS and 45 receiving sham tDCS. Within the active tDCS group, 25 participants were in the mindful-focus condition and 25 were in the mind-wandering condition, and in the sham tDCS group, 23 and 22 were in the mindful-focus and mind-wandering conditions, respectively.
Compared with the sham group, participants in the active tDCS condition reported significantly higher levels of state anxiety after worry induction (P =.016). Follow-up analyses showed a significant interaction between study condition and degree of state anxiety change between assessments (P =.007). The effect of study condition on anxiety was influenced by greater anxiety reactivity to worry induction in the active tDCS group (P =.004) and greater anxiety recovery in the tDCS group vs the sham group (P =.043).
Although tDCS did not appear to have a significant effect on negative thought intrusion, participants in the active tDCS group showed greater elevations in state anxiety after worry induction. These data suggest that tDCS “may interact with motivated engagement in negative patterns of cognition, such as worry, to produce greater emotional reactivity.”
The investigators noted that the use of a healthy sample may limit generalizability, and the study’s sample overall had low levels of anxiety. Even so, these data corroborate prior research, in which tDCS has been found to increase or decrease emotional reactivity to negative content, according to the patient’s current intent.
The researchers concluded, “the potential for neurostimulation to produce anxiogenic effects under specific conditions underscores the importance of preliminary experimental work with non/sub-clinical populations prior to application with emotionally vulnerable populations.”
Reference
Clarke PJF, Sprlyan BF, Hirsch CR, Meeten F, Notebaert L. tDCS increases anxiety reactivity to intentional worry [published online October 12, 2019]. J Psychiatr Res. doi:10.1016/j.jpsychires.2019.10.013
