Diagnosis of classic psychiatric illness in mentally handicapped individuals remains difficult. Manic-depressive illness has previously been reported in both pre-pubertal and pubertal children with a mental handicap and with a family history. This paper reports a case of manic-depressive psychosis in childhood, with no family history, short-cycle mood swings and good response to lithium therapy.

A case of folie à deux in a 29 year-old man with Down's syndrome, whose mother had a paranoid psychosis, is described. Successful treatment of the mother's illness also resulted in full recovery of the son without the need for medication.

A patient with Creutzfeldt-Jakob disease is described. Many alternative psychiatric diagnoses were considered, and the true situation only became apparent late in the clinical course.

A patient presenting with mixed affective symptoms was found to have active neurosyphilis after intermittent cognitive impairment suggested an organic cause. Most of these symptoms resolved after treatment with penicillin.

The case of a young woman presenting with three distinct episodes of pseudocyesis occurring concurrently with annual hypomanic illness is described, and the association between pseudocyesis and affective disorder discussed, with regard both to possible underlying psychopathology and to previously proposed psychoneuroendocrine mechanisms.

It has been suggested that viral infections, more prevalent in the winter months, might increase pregnancy and birth complications, which might in turn be responsible for the excess of winter-born patients with schizophrenia. In this study it was found that the rate of schizophrenia among high risk winter-urban births who had suffered a perinatal complication was significantly greater than that for those who had not thus supporting the hypothesis.

A case of Capgras syndrome associated with extreme violent behaviour is described. The patient's psychodynamics support the belief that the Capgras delusion initially arises from an altered affective response towards one or more others and proceeds to intolerable ambivalent feelings. This ambivalence is neutralised through the imagined existence of doubles.