We were most interested in the findings reported by Schaub et al., which demonstrate that both family history and obstetric complications are independently associated with age at onset in schizophrenia. These results are in accordance with those of previous studies examining the relationship between family history and age at onset R7415511CHDBJBJG; they also confirm the association between early onset and obstetric complications. We have now examined the relationship between age at onset and the number of definite obstetric complications (categorized into a four-level variable) in the pooled sample of subjects with schizophrenia. The proportion of subjects with onset before 21 years was higher in subjects with three and more obstetric complications (68.8% of 16) than in subjects with two obstetric complications (64.0% of 25), one obstetric complication (54.5% of 101), and no obstetric complications at all (46.7% of 323). A significant linear trend was found in the association between the dependent variable, age at onset (categorized into a binary variable, <22 versus 22 years), and explanatory variable, the four-level variable "number of obstetric complications," in a model fitted with the variable "study" (weighted average odds ratio for linear trend=1.32; 95% confidence interval=1.0–1.69; likelihood ratio=4.03, df=1, p=0.04). There was no evidence for heterogeneity across different studies. This result indicates that the higher the number of definite obstetric complications, the more likely the onset before 21 years. This dose-response relationship adds further evidence supporting the hypothesis that obstetric complications are involved in the pathophysiology of early-onset schizophrenia.