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The present study is concerned with what is inherited in mental disorder. Is it an unspecific tendency to mental disorder, is it specific symptoms or features such as age of onset, course or outcome, or is it psychiatric diagnosis? The study of pairs of relatives with mental disorder is certainly the best approach to investigating the problem of what is inherited. Unfortunately there has been a paucity of studies primarily dealing with this particular problem.
Ming T. Tsuang (Wed,) studied this question.