Heart rate variability is a trait marker of major depressive disorder: evidence from the sertraline vs. electric current therapy to treat depression clinical study - Brunoni, Andre Russowsky; Kemp, Andrew H.; Dantas, Eduardo M.; Goulart, Alessandra Carvalho; Nunes, Maria Angélica; Boggio, Paulo S.; Mill, José Geraldo; Lotufo, Paulo A.; Fregni, Felipe; Benseñor, Isabela M. (International Journal of Neuropsychopharmacology, 2013)