Age-of-Onset in Schizophrenia and Schizotypal Disorders

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Abstract
Age-of-onset data were gathered on 93 chronic schizophrenic probands and 57 affected (mainly schizotypal) siblings. Of affected individuals, 55% were ill before age 20 yr and 14% had their onset before age 14% yr. The risk period for schizophrenia and schizotypal personality disorders terminated at age 40%. Age-of-onset did not distinguish paranoid from nonparanoid schizophrenics, or definite from probable schizotypal personalities. Schizophrenic and schizotypal subjects were similar in their age-of-onset patterns. Sex effect on age-onset was not present. A square-root normal distribution gave the best fit to the data. The implications of these findings for schizophrenia research were discussed.