Atypical antipsychotics and some other psychotropic drugs such as valproate, lithium or mirtazapine are known to induce several metabolic complications. However there is an inter-individual variability in developing metabolic features which may be explained by clinical and genetic factors.

To determine whether weight gain and/or appetite change after one month are predictors for a weight gain after 3 and 12 months of treatment.

A longitudinal clinical and pharmacogenetic study is presently ongoing in the Department of Psychiatry-CHUV. Several clinical data have been recorded over one year following the introduction of psychotropic treatment. 406 patients with weight at baseline, after one month and with at least a third weight measure during the first year of treatment were included in the present study.

Using Receiver Operating Characteristic (ROC) analyses, an initial weight increase of 5% was found to be a good predictor for a consequent weight gain at 3 months (ROCAUC=77) and one year (ROCAUC=68). By using a generalized linear mixed model corrected by several confounders, this weight change of 5% was found to be significantly associated (p-value<0.0001) with an important weight change (10 to 20% increase from baseline value) over one year. Appetite was not found to be good a predictor of weight gain over one year.

An initial weight gain of 5% during the first month following an introduction of atypical antipsychotics, lithium, valproate and/or mirtazapine is a predictor for further weight gain and should be a warning sign to introduce weight lowering strategies.