title: Intellectual developmental disorder in adult psychiatry: A 24-year register study.
abstract: BACKGROUND
  Intellectual developmental disorder (IDD) may pre-dispose for mental health disorders. It is sometimes debated whether the needs of this group are adequately met in general psychiatry. However, little is known about patients with IDD in the psychiatric clinical setting-occurrence, clinical diagnoses, or service use.
  
  
  OBJECTIVE
  This study aimed to assess the number of adult patients diagnosed with IDD in a psychiatric clinic, their psychiatric diagnoses, and their use of psychiatric services.
  
  
  METHODS
  Individuals with registered IDD diagnoses were identified in a university hospital adult psychiatric clinic register comprising 67 384 patients.
  
  
  RESULTS
  IDD had been diagnosed in 0.6% of the patients. Psychotic disorders were the most common co-existing psychiatric diagnoses (25.5%). In 21.8% no psychiatric diagnosis other than IDD was registered. More than 50% had been inpatients; 21% had been compulsorily admitted. Patients with IDD had required a mean of five hospital beds per day.
  
  
  CONCLUSIONS
  The percentage, 0.6%, of IDD diagnoses was lower than estimates of the prevalence of IDD in the general population. This may reflect a lower need for psychiatric care, barriers to access services, or diagnostic over-shadowing. One fifth of the patients in this study had no psychiatric diagnosis beside IDD, which may be due to diagnostic difficulties, or other problems (e.g. somatic or behavioural disorders) leading to psychiatric contact. Since patients with IDD use the equivalent of five inpatient beds every year, it is suggested that it may be worthwhile to consider specialized psychiatry with expertise in IDD, even though this group is small.
authors.affiliation: a Department of Clinical Sciences/Psychiatry , Lund University , Sweden ;|b Gillberg Neuropsychiatry Centre , University of Gothenburg , Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Nylander
authors.affiliation: b Gillberg Neuropsychiatry Centre , University of Gothenburg , Sweden.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Fernell
authors.affiliation: b Gillberg Neuropsychiatry Centre , University of Gothenburg , Sweden.
authors.forename: Christopher
authors.initials: C
authors.lastname: Gillberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015897:Comorbidity; D005260:Female; D006778:Hospitals, Psychiatric / Q000706:statistics & numerical data*; D006801:Humans; D008607:Intellectual Disability / Q000453:epidemiology*; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology* / Q000523:psychology; D008875:Middle Aged; D015995:Prevalence; D012042:Registries / Q000706:statistics & numerical data*
keywords: Intellectual developmental disorder/IDD; concomitant psychiatric disorder; service use