The Kaiser Family Foundation issued a study, See No Evil: How Internet Filters Affect the Search for Online Health Information. The focus of the study was how the choice of the ‘least’, ‘intermediate’ or ‘most’ restrictive web filtering options available through six high profile systems (8e6, CyberPatrol, N2H2, Smartfilter, Symantec and Websense), impacted access to both pornography and health related information from web sites.
The foundation has made the full-text of the study available in PDF only, but it is broken down into over half a dozen parts. Use this link to access a list of the various portions of the report. In addition, the full-text of the study was published in the December 11, 2002 issue of the Journal of the America Medical Association (subscription req’d), under the title, “Does Pornography-Blocking Software Block Access to Health Information on the Internet?”, by Caroline R. Richardson; Paul J. Resnick; Derek L. Hansen; Holly A. Derry; Victoria J. Rideout. JAMA. 2002;288:2887-2894.