To date, the strongest support for noninvasive brain stimulation techniques in clinical neuropsychiatry (and the only FDA-approved therapeutic indication) comes from the treatment of certain forms of medication-resistant depression. The potential utility of brain stimulation techniques for treating depression was illustrated in several early studies that demonstrated that rTMS to prefrontal cortex had effects on mood (George et al., 1996; Pascual-Leone et al., 1996b). Based on these findings, one early study conducted a trial of daily high-frequency versus sham rTMS to left or right dorsolateral prefrontal cortex, with each site stimulated for five consecutive days (Pascual-Leone et al., 1996a); they showed that only high-frequency rTMS to the left dorsolateral prefrontal cortex significantly improved depression scores, with the effects lasting for approximately two weeks. A large number of subsequent trials have been carried out, with the majority finding high-frequency rTMS to the left dorsolateral prefrontal cortex to be effective in relieving symptoms of depression. Several studies have also looked at the effects of low-frequency (inhibitory) rTMS to the right prefrontal cortex, with most finding that inhibitory rTMS to the right prefrontal
