NEURODEVELOPMENTAL DISORDERS: Edited by James C. HarrisThe co-occurrence of mental disorders in children and adolescents with intellectual disability/intellectual developmental disorderMunir, Kerim M. Author Information aUniversity Center for Excellence in Developmental Disabilities (UCEDD), Division of Developmental Medicine, Boston Children's Hospital bDepartment of Psychiatry, Boston Children's Hospital cDepartments of Pediatrics, Psychiatry and Holmes Society, Harvard Medical School, Boston, Massachusetts, USA Correspondence to Kerim M. Munir, Developmental Medicine Center, Fegan-10, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA. Tel: +1 617 355 7166; e-mail: [email protected] Current Opinion in Psychiatry 29(2):p 95-102, March 2016. | DOI: 10.1097/YCO.0000000000000236 Buy Metrics Abstract Purpose of review The study summarizes supportive epidemiological data regarding the true co-occurrence (comorbidity) and course of mental disorders in children with intellectual disability/intellectual developmental disorders (ID/IDD) across the lifespan. Recent findings Published studies involving representative populations of children and adolescents with ID/IDD have demonstrated a three to four-fold increase in prevalence of co-occurring mental disorders. The effect of age, sex, and severity (mild, moderate, severe, and profound) and socioeconomic status on prevalence is currently not clearly understood. To date there are no prevalence estimates of co-occurring mental disorders in youth identified using the new DSM-5 (and proposed ICD-11) definition of ID/IDD using measures of intellectual functions and deficits in adaptive functioning with various severity levels defined on the basis of adaptive functioning, and not intellectual quotient scores. Summary The true relationship between two forms of morbidity remains complex and causal relationships that may be true for one disorder may not apply to another. The new conceptualization of ID/IDD offers a developmentally better informed psychobiological approach that can help distinguish co-occurrence of mental disorders within the neurodevelopmental section with onset during the developmental period as well as the later onset of other mental disorders. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.