Polysomnographic phenotypes in developmental disabilities.

People with developmental disabilities express a number of unique behavioral patterns that have both phylogenetic and ontogenetic origins. Researchers have identified distinct behavioral phenotypes among developmental disabilities expressed as language development, cognitive profiles, adaptive behavior, and self-injury/aggression. In this article, we discuss evidence for the presence of polysomnographic phenotypes in developmental disabilities. Researchers using behavioral and/or electrophysiological measures have identified differences in sleep architecture among people with autism, Down syndrome, and fragile X syndrome. In general, the greater the level of mental retardation, the less time spent in rapid eye movement sleep. The presence of autism or Down syndrome is associated with fewer and briefer bouts of rapid eye movement sleep, and total sleep time. Autism is also associated with greater levels of undifferentiated sleep. These findings for autism and Down syndrome contrast with fragile X syndrome whose sleep architecture anomalies appear to be a function of mental retardation level.