OVERVIEW: PCS is a constellation of clinical symptoms including physical (i.e. headaches), cognitive (i.e. memory), and behavioral disturbances. PCS is associated with significant morbidity in the child and his/her family), and yet there are no evidence-based medical treatments available. This suggests an urgent need to develop novel treatment options to improve outcomes for children suffering from PCS. Melatonin has several relevant mechanisms of action, and neuroprotective effects. Recent research suggests that the explanations for persistent PCS symptoms may be due to alterations in neurotransmissions and neuronal circuitry, particularly involving the dorsolateral prefrontal cortex (DLPFC). Investigators have two specific aims: