Genetic aspects in chronic schizophrenia. Morbidity risks and contributory factors

112 schizophrenics, over 55 years old, and their relatives were studied. Aims of the study were (1) to evaluate the assumption that using an appropriate selection of probands and methods of the morbid risk estimation, one may expect to obtain a higher (and probably more realistic) value of risk to children; and (2) to assess the possible influence of patients' and relatives' characteristics on the magnitude of the morbid risk. The main results were (1) the values of risks (0.04 +/- 0.02 for spouses; 0.08 +/- 0.02 for siblings; 0.17 +/- 0.04 for offspring); (2) the risk to siblings and to children increased with the numbers of other relatives affected; (3) no clinical symptoms in probands (evaluated throughout the lifetime course of the disease) were associated with an increased/decreased value of risk to any class of relatives.