The Ham D 6 is more homogenous and as sensitive as the Ham D 17

Abstract

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 ( n = 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.