Hypothesis of the optimal therapeutic effect of transcranial direct current stimulation (tDCS) for psychiatric disorders: Integration of positive cognitive tasks during the neuroplastic process

Transcranial direct current stimulation (tDCS) is a promising intervention for psychiatric disorders; however, little is known with regards to the optimal regime. As cognition, either spontaneously generated by patients or guided by treatment, is important in psychiatry, we have proposed a model that integrates cognition activity with the biological mechanisms of the therapeutic effect of tDCS in psychiatric disorders. We propose that the valence of the outcome of these mechanisms may be determined by the cognitive activity of the patient before or during tDCS treatment. This hypothesis implies that proper cognition activity may work in cooperation with tDCS to achieve the maximum treatment effect. Negative cognition may decrease or even reverse the positive effect of tDCS. According to this hypothesis, the performance of explicit tasks or instructions before, during, or after tDCS is important. Harm caused by misuse of home-made tDCS equipment is also addressed in this hypothesis.