In summary, the present results seem to cast doubts on the suggestion that people with ID and autism may have an increased risk for psychiatric disorders. However, although people with autism may not fulfill the conventional ICD-10 criteria, they still may suffer from psychiatric symptoms and maladaptive behaviors. Firm conclusions on the relationship between low-functioning autism and psychiatric co-morbidity may be premature in light of the diagnostic difficulties, inherent methodological problems, and possible overlap between autistic behaviors and those relating to other disorders. In this respect, diagnostic tools designed to address the specific needs of people with autism could contribute substantially. In terms of mental health policy planning, a stronger evidence base is needed prior to committing resources for clinical services.