The overarching purpose of this pilot study is to collect preliminary data regarding the variability of weight gain associated with lurasidone (Latuda©) treatment of antipsychotic naive children and adolescents in order to inform decisions about including a lurasidone arm in a future large scale trial of different approaches to minimize antipsychotic associated weight gain in the pediatric population. In adults, lurasidone appears to cause minimal weight gain. The participants will be 6-19 years old with psychotic spectrum, mood spectrum, or autism spectrum disorders. They will have 4 weeks or less of lifetime antipsychotic exposure.