Background: Transcranial direct current stimulation (tDCS) applied to the left dorsolateral prefrontal cortex (dlPFC) might be a promising treatment strategy for depression. As disturbances in psychomotor activity are one of the key features of unipolar depression are, we aimed to evaluate the behavioral effects of ten tDCS sessions over a 5-day period on psychomotor retardation in depressed patients.
Methods: Twenty-three treatment-resistant depressed patients received either active or sham anodal tDCS to the left dorsolateral prefrontal cortex (2 mA, 10 sessions over 1 week). Psychomotor functioning was registered by means of observer ratings (Salpêtrière Retardation Rating Scale-SRRS) and objective measures (kinematical analysis of movements, automatic imitation).
Results: tDCS sessions resulted in improvements on SRRS scores, although active tDCS was not significantly superior to sham tDCS on the kinematical parameters. Furthermore, no general additional antidepressant effect of tDCS was observed. The relatively small sample size and the short periods of observation should be considered when interpreting these results.
Conclusion: tDCS did not induce a clinically relevant effect on psychomotor function in active and sham stimulation groups.
Keywords: major depressive disorder; psychomotor symptoms; retardation; transcranial direct current stimulation.