To have a larger sample of poor metabolizer subjects, we plan to enroll at least 8 additional subjects who are on stable treatment with risperidone, and perform risperidone pharmacokinetics analyses. Prospectively enrolled subjects (n = 8) will be CYP2D6 poor metabolizers and will include White / Caucasian subjects, of any socioeconomic status, and will be recruited from inpatients or outpatients at Cincinnati Children's Hospital