AGE AT ONSET IN SIBLING PAIRS WITH SCHIZOPHRENIA AND SCHIZOAFFECTIVE DISORDEROsnat Karni*, Avi Yakir, Kyra Kanyas, Neil Turetsky, Bernard Lerer.Biological Psychiatry Unit, Hadassah -Hebrew University Medical Center, Jerusalem, Israel Affected sibling pairs are a cornerstone of current efforts to elucidate the molecular genetics of schizophrenia (SCZ). Research samples generally include affected siblings with diagnoses such as schizoaffective disorder (SA) and unspecified functional psychosis (UFP) as well as SCZ. We have studied 72 independent pairs of siblings of whom 34 (47.2%) were concordant for SCZ and 12 (16.7%) were concordant for SA. 26 pairs (36.1%) were discordant for diagnosis. Age at onset was defined as: 1) the age at which the subject first received psychological treatment of any type (AFPT), 2) from the OPCRIT Age at Onset Item (Onset_A), and, 3) as age at first psychiatric hospitalization (AFPH). Considering the entire group of 72 affected pairs, there was no significant correlation between the sib pairs for age at onset according to any of the definitions. When the analyses were confined to sibling pairs concordant for diagnosis (SCZ-SCZ or SA-SA) the relationship for all the variables reflecting age at onset of illness became significant (AFPT r=.34, p=.02; AFPH r=.40, p=..02; Onset_A r=.36, p=.02). Inclusion of sib pairs discordant for diagnosis (i.e. SCZ-SA, SCZ-UFP or SA-UFP pairs) in genome scans could contribute to the great variability observed between samples in the results of linkage analyses. (Supported by the German Israel Foundation for Scientific Research).
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