Time-to-pregnancy and risk of schizophrenia.

Schizophrenia has been linked to advanced paternal age, but the explanation is unknown. We questioned whether the incidence of schizophrenia would be related to male reproductive capacity, as reflected in the time taken to conceive. We measured the incidence of schizophrenia in relation to time to conception in a sub-group of 12,269 in the Jerusalem cohort whose mothers, interviewed post-partum, reported that the pregnancy had been intended. Compared with those conceived in less than 3 months, the unadjusted relative risks (RR) of schizophrenia associated with conception-waits of 3-5, 6-11 and 12+ months were 1.10 (95% confidence interval, 0.62-1.94), 1.41 (0.79-2.52) and 1.88 (1.05-3.37) with p for trend=0.035. This trend was attenuated somewhat by adjusting for paternal age, and was observed more strongly in offspring of fathers aged 30+ (p=.010). These findings suggest that factors associated with fecundability, either male or female, may contribute to the risk of schizophrenia.