The Ham D6 is more homogenous and as sensitive as the Ham D17

Objective. - Using the data of a positive d.b.c.t. comparing an hypericum extract (W55570) to placebo in depressed patients we explored whether the Ham D-6 was unidimentional and in case of a positive answer whether the total score was as sensitive as the total score of the Ham D-17. Methods. - The study was a 6 weeks double blind placebo controlled trial comparing 300 mg of hypericum t.i.d (n = 186). to placebo (n = 189), in patients with a single or recurrent depression according to DSM-IV. Superiority of hypericum versus placebo on the main outcome criterion (HDRS 17) was already published. The unidimensionality of the Hamilton depression scale 6 and 17 items were tested using a Mokken scale analysis. The effect size according to the initial severity of depression was calculated on the ITT last observation carried forward population. Results. - The Ham D-6, covering the core symptoms of depression was unidimensional, implying that improving this score reflects a true antidepressant effect. The Ham D-17 was not unidimensional. Hypericum was an effective antidepressant in patients with a pre-treatment score of 12 or more (n = 208) on the Ham D-6, the effect size was 0.46. No difference with placebo was observed for those with a score of less than 12 (11 - 167). Conclusions. - For the evaluation of an antidepressant effect, because of its specificity and sensitivity, the Ham D-6 should be used as a primary outcome measure rather than the Ham D-17. (c) 2007 Elsevier Masson SAS. All rights reserved.