Notwithstanding intermediaries between the genetic phenotype of poor metabolisers and the clinical phenotype of ADRs, the aim of this pilot study was to examine whether a predicted CYP2D6 PM phenotype would emerge in a naturalistic cohort for which such phenotype would be most likely, i.e. a cohort with clinically marked movement disorders and/or weight gain. This evidence concerns the gene CYP2D6 and movement disorder.