Most children with Down syndrome (DS) do not have a psychiatric or neurobehavioral disorder. Current prevalence estimates of neurobehavioral and psychiatric co-morbidity in children with DS range from 18% to 38%. We have found it useful to distinguish conditions with a pre-pubertal onset from those presenting in the post-pubertal period, as these are biologically distinct periods each with a unique vulnerability to specific psychiatric disorders.
Source: George Capone, Parag Goyal, William Ares, and Emily Lannigan