This effect was conditioned on interactions with severity ( t@ = @ ; P = @ ; NNT ,@ ) and chronicity ( @ = @ ; P = @ ; NNT ,@ ) such that the advantage for combined treatment was limited to patients with severe , nonchronic MDD ( @ % vs @ % ; n = @ ; t@ = @ ; P = @ ; HR , @ ; @ % CI , @-@ @ ; NNT , @ ; @ % CI , @-@ ) .