Over-indebtedness vs physical workload? Laura Punnett, Dept. of Work Environment, Univ. of Mass. Lowell, USA 16 December 2009 There is no question that over-indebtedness certainly could be an important source of psychosocial strain, especially in the current time period. However, it is more common in those of lower SES, and several recent studies have shown that the relation of SES to LBP is at least partially mediated by heavy physical workload, which has a well-documented effect on LBP and is far more common in low-SES jobs. The failure to consider physical work demands as a possible confounder or mediating variable is a serious limitation on the interpretation of these results. Competing interests No competing interests to declare.