Side effect profile and comparative tolerability of 21 antidepressants in the acute treatment of major depression in adults: protocol for a network meta-analysis by Tomlinson, A, Efthimiou, O, Boaden, K, New, E, Mather, S, Salanti, G, Imai, H, Ogawa, Y, Tajika, A, Kishimoto, S, Kikuchi, S, Chevance, A, Furukawa, T, Cipriani, A