[Delay of the antidepressant effect: clinical studies]

The first controlled trials of antidepressants show up a delay of antidepressant effect to one or two weeks, with sedative or stimulant early effects. More recently, several controlled trials founded on more stringent criterions (DSM III, period of pre-therapeutic placebo of one minimal week, frequent quotations etc.) have showed up a delay of antidepressant effect assigned between the fourth and the sixth week, with all antidepressant drugs. Nevertheless, there are more early effects, either specific antidepressant but incomplete either non specific (sedative, stimulant). These early effects are more marked with the antidepressant drug than with the PBO, but they have not a predictive value of terminal response. Several factors have an influence on the delay of antidepressant effect. The clinical characteristics are not correlated with this delay. The intravenous administration does not reduce the length of this delay. The pulse loading doses with intravenous and oral antidepressant drug seem to reduce the length of this delay. The most important factor is the placebo effect (Quitkin et al.). Nevertheless, the differences of efficacy between antidepressant and PBO appear only towards the third week. There are some differences during the first two weeks. In fact the PBO effect is early and late longer than the antidepressant drug. With PBO, when the improvement is progressive and fasting, it is a spontaneous remission. These data have practical implications if we must know the delay of antidepressant drug.