Does workload cause work-home interference or is it the other way around?

The present study was designed to investigate the causal relationships between work-home interference (WHI) and one of its strongest correlates, quantitative workload. Two-phase longitudinal data (with a 1-year time lag) were gathered from 828 Dutch police officers. Drawing on the effort-recovery model, and in line with the current WHI literature, we hypothesized that relatively high workload precedes increased levels of WHI 1 year later ('normal' causation). In addition, we tested the alternative hypothesis that relatively high levels of WHI predict increased workload 1 year later ('reversed' causation). Results of hierarchical regression analyses showed that workload and WHI have causal and reversed causal relationships across time, supporting both hypotheses (although effect sizes are limited). Accordingly, these findings suggest that workload is not merely an antecedent of WHI but is also a potential consequence. Copyright (C) 2007 John Wiley & Sons, Ltd.