ASD and psychoses - misdiagnoses or comorbidity? Findings in a clinical practice

Background: Since autism was originally described, its relationship to psychotic disorders has been debated. With the recognition of autism spectrum disorders (ASD) in adults, this debate has become even more relevant.
Objectives:

To determine the number of patients with coexisting ASD and psychotic disorder in a clinical sample of adult patients referred for assessment.
Methods:

All patients were examined by a specialized team (psychiatrist and psychologist). Medical charts were reviewed, and a developmental history was always taken. Most patients were neuropsychologically tested with the WAIS-R or WAIS-III. The DISCO (The Diagnostic Interview for Social and COmmunication disorders) was used in several cases.
Results:

68 out of 476 consecutive patients had a clinical diagnosis of psychosis prior to assessment. In 12 a new diagnosis of ASD, instead of psychosis, was assigned. In 11 cases, psychosis and ASD coexisted. In 11 cases with a “psychosis only” diagnosis the DISCO was used. 10 of these cases, according to the DISCO algorithm, met criteria for PDD-NOS, which, however, could not be clinically verified.

Conclusions: These cases show that it is possible that psychiatric services sometimes misdiagnose psychotic disorders in adults whose problems are better described in terms of autism spectrum disorders. Furthermore, schizophrenia and other psychotic disorders or psychotic symptoms may be comorbid with ASD.
The figures must be interpreted with caution, since the patient group was a clinical sample referred to a highly specialized service for diagnostic assessment, and therefore biased to cases where diagnostic difficulties had been recognized. The numbers thus do not reflect the true ratio of “misdiagnoses” in patients given diagnoses of psychotic disorders. Nor can any conclusions be drawn about the true prevalence of comorbidity. Interestingly, the symptoms of atypical ASD may be similar to symptoms of psychosis, as shown in the DISCO results.