To limit genetic heterogeneity, this study focused on the widely extended pedigrees of Ashkenazi Jewish schizophrenic and autistic probands, to determine if similar causal mechanisms might obtain for both conditions. At least two previous epidemiological studies have demonstrated increased risk for schizophrenia in Ashkenazi Jews. The hypothesis posed is that increased prevalence of various rare autosomal recessive diseases among the Ashkenazim might contribute to the increased vulnerability to schizophrenia and to autism in this large genetic isolate. Rates of amyotrophic lateral sclerosis (ALS) and bleeding disorders were significantly increased among relatives of schizophrenic and autistic probands, compared to relatives of normal probands. These results suggest new candidate loci in schizophrenia and autism, particularly the chromosome 15q23-24 locus of the hexosaminidase A gene, causing various GM2 gangliosidoses, and the 21q22.1-q22.2 loci of the antioxidant, superoxide dismutase gene, and a cytokine receptor gene. (Goodman, A. B. (1994). A family history study of schizophrenia spectrum disorders suggests new candidate genes in schizophrenia and autism. The Psychiatric Quarterly, 65(4), 287-97.)
A number of studies have suggested a relationship between schizophrenia and autism, perhaps most recently Psychosis and Autism as Diametrical Disorders of the Social Brain by Bernard Crespi. It seems that schizophrenics and autistics often share family of origin, even though the brain structure and behaviors are not alike. If autistics often come with the first born and latest children of a mother, do schizophrenics have a similar birth order pattern?
