The purpose of this study is to establish the efficacy and safety of Circadin in children with neurodevelopmental disorders and to determine the dose, this randomized, placebo-controlled study is planned to evaluate the efficacy of a double-blind, 13 week treatment period with Circadin 2/5mg in improving maintenance of sleep, sleep latency and additional parameters in children with neurodevelopmental disabilities. The efficacy and safety of Circadin 2/5 mg will continue to be assessed during an open-label extension period of 13 weeks.