Table 4.

A summary of the main findings of the studies investigating the effects of TMS on the serotonergic system.

Serotonergic system
Study	Design	Population (n)	Intervention	Result
Kuo et al., 2016	Crossover randomized double-blind placebo-controlled study	Healthy volunteers. N=12	Four sessions of active tDCS of M1, after intake of placebo, dextromethorphan or citalopram	Chronic administration of citalopram prolonged and enhanced the LTP driven by anodal stimulation. Furthermore, it converted the LTD related to cathodal stimulation into facilitation. Both effects were reverted by dextromethorphan administration.