Two investigations were done to sec whether toxoplasmosis plays an important role or not as causative factor in mental retardation.
In the first investigation the Sabin Feldman test was done in 366 mental retarded patients. The incidence of positive test did not differ from the incidence in normal individuals. In the second test a normal sibling of the retarded patient was chosen as a control on admission of the patient in the institute.
Also in these groups (48 persons each) the percentage of the positive tests did not differ considerably.
In this study there was found no support for the concept that toxoplasma plays an important role as a causitive factor in mental retardation.