1. The prevalence of psychiatric disorder of various kinds among subjects aged 65 or over was studied by two complementary methods, which could be combined to obtain an estimate of the total prevalence.
(a) Domiciliary cases: 309 subjects with addresses in one of five areas chosen for the investigation were selected at random from the electoral register and all subjects living at home were interviewed.
(b) Institutional cases: A census was made of patients and residents in mental hospitals, geriatric wards and welfare homes on 1 November, 1960, and a psychiatric assessment was made of all those whose home address lay within one of the five areas.
2. The prevalence of organic brain syndromes was high (10.3 per cent.). Senile and arteriosclerotic syndromes were about equally common, but the former was diagnosed more frequently in women, the latter in men. Brain syndromes due to other causes occurred in 1.9 per cent.
In about half the cases the mental deterioration was severe and was similar in degree to that usually found in demented mental hospital patients.
Fewer than one-fifth were actually being cared for in a hospital or Home.
3. The total prevalence of all forms of functional disorder was 31 per cent., with a somewhat higher rate among women than men. This group of disorders included a wide variety of conditions, but neuroses were by far the commonest. The large majority of cases were not receiving any formal psychiatric treatment; fewer than one-tenth were under residential care of any kind.
4. Five per cent. of the domiciliary subjects suffered from a neurotic or an affective illness which was of at least moderate severity and had arisen late in life, constituting an entirely new development in the medical history. In the remainder, the illness was only mild, or recurrent, or consisted of an accentuation of long-standing personality traits. Six per cent. had had previous treatment.
5. Neither of the major functional psychoses, schizophrenia or endogenous affective disorder, could be identified with confidence among subjects seen at home, and all the active and established cases were already under care. But chronic, mild or incipient forms (including paranoid states) were judged to be present in about 3 per cent.
6. The findings demonstrate again that only a very small fraction of old people with psychiatric disorder are being cared for either as hospital in-patients or as residents of Homes. There is clearly an urgent need to extend the facilities for community care for this part of the population.
7. A review of the literature shows that the results of prevalence studies, where intensive methods have been used, are in quite good agreement.