Another intersection between science and policy is embodied in a recent report (PDF) from the Science Select Committee of the British Parliament on the relative harmfulness of different legal and illegal drugs. Notably, the survey ranks alcohol and tobacco as being more harmful than illegal drugs including cannabis, LSD, and ecstasy.
Setting aside methodological issues, the survey does reveal some ways in which our response to scientific information is conditioned by pre-existing understandings and practices. Why society feels that it should permit an adult to drink or smoke as much as they choose to (though not in public or before driving) but that it must actively forbid the use of some other substances has no clear logical basis. Any argument that can be used to justify legal tobacco (free individual choice, etc) could be just as easily applied to other substances on the select committee’s list. While scientific and ethical arguments can be made to bolster various positions, it seems that sheer momentum is the main determinant of policy.
I would be willing to guess that some prescription drugs – especially the anti-depressants given ever-more-readily to children and teenagers – would rank quite unfavourably, if subjected to the same type of analysis.