Further evidence for anticipation in schizophrenia

The term 'anticipation' is used to describe the increase in disease severity or the decrease in age of onset in succeeding generations within families. This phenomenon has been related to expansion of trinucleotide repeat DNA sequences in some genetic illnesses. We examined age of onset among two generations in familial schizophrenia. Twenty-six unilineal pedigrees previously ascertained for linkage studies were used. We defined the older generation as G1 and the younger generation as G2. Cumulative survival analysis for intergenerational pairwise comparisons in groups G1 and G2 showed a significantly earlier age of onset in G2 (10 years earlier). Additional analyses, which took into account some biases such as the censoring effect of age at interview and preferential ascertainment of late-onset parents, did not modify the results. No evidence for genomic imprinting was found in our sample. We conclude that anticipation occurs in our sample of familial schizophrenia.