Swedish Council on Technology Assessment in Health Care (SBU). Chapter 4. Methodological aspects in sickness-absence research.

Several methodological aspects concerning research on sickness absence and disability pension are noteworthy, including: empirical research is being conducted within many different disciplines using various study designs; progress in theory development has been slow and weak; several outcome measures are used; terminology varies widely; and comparative research is difficult to conduct since insurance systems differ over time and among nations and employers.