A paper in the latest Journal of Advanced Nursing looks at these questions:
'What does qualitative research tell us about the facilitators and barriers to accessing and complying with tuberculosis treatment?"
"What does qualitative research tell us about the diverse results and effect sizes of the randomized controlled trials included in the Cochrane review?"
A Cochrane review apparently did not find anything to distinguish directly observed treatment with people treating themselves.
The abstract is at http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-2648.2006.04092.x and the bibliographical details are:
Jane Noyes, Jennie Popay (2007). Directly observed therapy and tuberculosis: how can a systematic review of qualitative research contribute to improving services? A qualitative meta-synthesis. Journal of Advanced Nursing 57 (3), 227–243.