Measurements of rheumatoid factor were done on the sera of 86 patients consecutively admitted to an acute psychiatric service. Sixty-three percent of those with endogenous depressions and 35 percent of those with schizophrenia had positive titers. When the schizophrenic patients were subdivided on the basis of affective state, it was found that 65 percent of those with depressive symptoms, and only 21 percent of those without depressive symptoms, had positive titers. The authors conclude that depression would seem to be associated with a nonspecific effect involving immunological mechanisms.Abstract Teaser