Identification of anxiety and other psychiatric disorders in individuals with autism and intellectual disability

The thesis addresses the conceptual overlap between autism and psychiatric disorders, and the delineation between them. There is considerable conceptual overlap between autism and psychiatric disorders and similar behaviours may be indicators of both phenomena. Differentiating conceptually between these disorders is therefore a prerequisite for developing more accurate and reliable psychiatric diagnoses in individuals with autism. The conceptual boundaries between autism and psychiatric disorders are explored, and the results applied as a basis for further explorations. The aim is to contribute to an improved conceptual understanding of both autism and psychiatric disorders and the relationship between them. The thesis contains four papers. Paper one is a conceptual analysis, and demonstrate that it is possible to differentiate conceptually between symptom descriptions of autism and of four major psychiatric disorders (psychosis, depression, anxiety, and obsessive compulsive disorder, OCD), as well as between the four psychiatric disorders. Paper two is a pilot study and the first validation of a new screening checklist: the Psychopathology in Autism Checklist (PAC), which was constructed on the basis of the results from the conceptual analysis. Paper three is a screening study of a representative sample. The study also includes a comparison with a representative sample of persons with ID only. Paper four addresses the assessment of anxiety in more detail. The study explores the recognition of anxiety symptoms and aims to provide suggestions for the assessment of anxiety in individuals with autism and ID. The differentiation of symptoms related to autism and to psychiatric disorders demonstrated in the present thesis may contribute to a better conceptual understanding of the phenomena and reduce the difficulties related to identifying psychiatric disorders in individuals with autism and intellectual disability (ID), facilitate increased awareness among professionals, and improve the quality of the mental health care for this group. The assumed high levels of psychiatric comorbidity among adolescents and adults with autism and ID have been supported by the findings in the present thesis, although the levels are lower than in some of the highest reports. The PAC is not a diagnostic instrument, and an accurate diagnostic evaluation requires additional information from informants with thorough knowledge about the individual and the individual’s changes in behaviour and mood over time. The PAC may, however, contribute to the identification of people within this population who are at risk for having mental health problems and thereby to their access to specialized mental health services