Laterality patterns in relation to schizophrenia patients' age at onset.

Based on numerous findings of an abnormal laterality in schizophrenia disorder, we hypothesized that handedness and lateral preferences may affect the age at onset in schizophrenia patients. Two samples of schizophrenia patients, the first a sample of 34 right-handers and 42 left-handers and a replication set of 84 right-handers, were examined with regard to age at onset considering handedness and the four Luria's signs (arm folding, hand clasping, familial sinistrality and eye dominance) as well as gender. The association between these parameters and age at onset was investigated by means of multiple regression analysis. Our analyses revealed that right-handers with right arm folding and left-handers with left arm folding showed an early age at onset, while in the late age at onset the opposite preferences prevailed. Apart from arm folding, signs of ambilaterality, i.e., left eye dominance in right-handers and familial sinistrality in left-handers were additional predictors for an early age at onset. Remarkably, all observations found in the first right-handed sample were confirmed in the right-handed replication set. We conclude that among the many different factors specific lateral preferences should also be considered in assessing patients who are at risk of psychosis.