Phenotypic manifestations for young children with fragile X syndrome (FXS) include: anxiety, sensory processing challenges, global language and communication deficits and intellectual and developmental disabilities. Many of these symptoms can be treated with medications, including selective serotonin reuptake inhibitors (SSRIs). However to date a clinical trial has not been conducted for children under five years old.

This study investigated the following question: Are there group differences on developmental outcome measures for those children treated with sertraline compared to placebo?