Informed consent in experimentation involving mentally impaired persons: ethical issues.

The problem of experimentation involving subjects whose mental condition prevents them from understanding information and providing proper informed consent has been addressed in various codes, declarations, conventions, treaties and regulations adopted by national, international and supranational institutions and authorities. This article summarizes the basic ethical criteria these documents provide and stresses the historical development from the nearly total exclusion of incapacitated subjects, established in the mid-twentieth century, to their contemporary inclusion in clinical trials on certain ethical conditions. The problem of proxy consent by legal representatives for participation in clinical trials is addressed particularly in reference to current Italian regulations. Exceptions to human experimentation requirements in emergency situations are also briefly discussed.