Prader Willi Syndrome is characterized by a range of well-recognised symptoms including overeating and other food obsessions, rage attacks or tantrums, skin-picking, obsessions, abnormalities of sleep breathing and body temperature, and diificulties in learning and understanding social cues. These difficulties have serious impacts on the health of individuals with PWS and their families. There is evidence from brain studies that PWS individuals have abnormalities in a part of the brain called the hypothalamus that are likely to be causing these abnormalities. A natural hormone derived from the hypothalamus, oxytocin may deficient. In a clinical trial, the evaluating oxytocin nasal spray to assess its efficacy in improving these problems. FPWR funding will support the accompanying analysis of patient blood samples to determine how plasma levels of oxytocin and other appetite related hormones change in PWS as a result of chronic intranasal treatment with oxytocin. Importantly, this study will also examine whether intranasal OT has lasting effects on the circulating levels of these various factors that can be correlated with improvements in appetite and sociability in the participants given intranasal oxytocin.