[Problem of molecular psychiatry in view of the trinucleotide repeat expansion disease].

Recent findings of trinucleotide repeat expansion diseases (TNED) have suggested that some familial psychiatric diseases may be caused by the same molecular mechanisms. Anticipation and imprinting phenomena have been shown to be present in families with schizophrenia. Studies by means of the Repeat Expansion Detection (RED) showed the frequencies of the expanded CAG repeat in schizophrenia was larger than those in normal control subjects. However, there are several problems; anticipation may be caused by not only TNED but also by unknown mechanisms and biases; RED method cannot detect the specific TNE, and TNE which was unrelated to a disease was found.