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Fifty-seven cognitively impaired elderly had significantly elevated serum IgG (P less than or equal to 0.005) and IgA (P less than or equal to 0.01) levels and similar IgM levels, compared to a population of 65 elderly matched for age and sex, who did not manifest cognitive impairment. These findings are compatible with a current hypothesis that immunological factors may be important in the cognitive disorders observed with increasing frequency among the aged.

In 42 patients with cognitive dysfunction (senile dementia) significant correlations between immunoglobulins and various tests of intelligence were observed. Serum IgG emerged as the single best predictor of behavioural status. There is need for further research in this field.

Serum antibody titres to eight neurotropic viruses were measured by enzyme immunoassay in 450 psychiatric in-patients and 143 controls. A seasonal variation in schizophrenic births was observed, with a peak incidence between March and April. Both herpes simplex virus and cytomegalovirus antibody titres correlated with age and, when this was controlled for, no significant differences emerged between any patient group and the controls. Mumps antibody titres were significantly lower in patients with mental subnormal and neurosis or personality disorder; measles and rubella antibody titres were lower in male but not female mentally handicapped patients; males had lower antibody titres to mumps, cytomegalovirus and Epstein-Barr virus than females in all groups. A decrease in mumps antibody titres was also found in schizophrenics if the medication factor was excluded. These low antibody titres may indicate an impaired immune response. Thus perinatal or childhood subclinical viral infections of the central nervous system, particularly of mumps, might lead to a range of possible psychiatric outcomes in later life.

In ten patients with presenile dementia of the Alzheimer type and in a control group the levels of the different immunoglobulins were determined in both serum and cerebrospinal fluid (CSF), and gel electrophoretic techniques used to determine possible oligoclonal bands in the gamma-globulin region. There is no indication that patients with Alzheimer disease produce immunoglobulins within the central nervous system.