Sleep is a phenotype. Developmental problems in children, particularly those occurring during the prenatal period, can override or masquerade as genetic influences, and contribute in this phenotype. Sleep problems are especially prominent in children with hyperactivity and oppositionality. When coexisting, these behavioral problems alter the sleep pattern in an additive manner. Results of the current study suggest that fairly different in expressions, prevalence of sleep onset disorders, sleep fragmentations, nocturnal breathing disorders, and reduced sleep efficiency are twice higher in children with Autism, Rett, Tourettes, Angelman and Hellers syndromes. Sleep symptomatic, especially parasomnias, are not related to children's cognitive and intellectual deficits, except of Tourettes children whose cognitive scores are negatively related to sleep onset parameters. Sleep-maintenance insomnia and inefficient sleep have moderate associations with central apnea, arousal index - having acceptable sensitivity (87%), but low specificity (26%). Exogenous melatonin improves sleep-wake cycles, advances sleep-onset latency, however, it does not impact on arousal index. The optimal dosage and duration of treatment with melatonin are far to reach a scholarly consensus and are discussed here. Our findings inform extensions of further research in Mozarts effect - as a natural trigger of endogenous melatonin.