It has been suggested recently that the prevalence of autistic disorder may be rising. No prevalence study specifically among learning disabled children exists and so this study was prompted.

Method. 767 children with a learning disability who attended 16 different special schools in the Grampian region of north-east Scotland were studied for a diagnosis of autistic disorder according to the DSM–III–R criteria. The study was conducted in three stages. In the first screening stage, a questionnaire was completed for each child by their teachers. In the second stage, teachers completed another questionnaire based on DSM–III–R criteria for autistic disorder. A final diagnosis was made on the basis of examination and information gathered from the questionnaires.

Questionnaires were completed for 634 (82.7%) children. 14.3% of children with a learning disability fulfilled the diagnostic criteria for autistic disorder. There was a male: female ratio of 3:1. This gave a 9 per 10 000 minimum prevalence of autistic disorder among all school-age children in the Grampian region. There was a higher prevalence of autistic disorder in the cities compared with rural areas. The prevalence did not change with age but increased with decreasing IQ.

Depression occurs commonly in people with Down's syndrome, although there is little published about this association. This study explores the limitations of Diagnostic Criteria for Research, based on ICD-10 (DCR) and DSM–III–R depressive criteria.

Case note examination identified 42 adults with Down's syndrome who have sustained 56 depressive episodes. The clinical features are reported.

All episodes were diagnosed as depression. DSM–III–R criteria for major depressive episode were met by 50% of the episodes. DCR for depressive episode of at least mild severity were fulfilled by 68%.

These criteria were unduly restrictive for this group. Commonly occurring symptoms are not included in the criteria, while certain criteria items never occurred. Criteria should be modified to facilitate future research.

Neuroimaging of a treatment-resistant patient with schizophrenia revealed the existence of cerebral hemiatrophy. The association of schizophrenia with cerebral hemiatrophy has not previously been reported.

Neuroimaging with X-ray computerised tomography showed marked reduction in the volume of the left cerebral hemisphere with secondary enlargement of the left lateral fissure and cortical sulci. High resolution cranial single-photon emission computerised tomography showed a functional deficit of the regional cerebral blood flow in the left lateral parietal and left temporal lobes.

Cerebral hemiatrophy may belong to the lengthening list of neurodevelopmental cerebral anomalies associated with schizophrenia.