There’s an excellent post about the use of vivid imagery and provoking fear through public health advertising over on the Brief Addiction Science Information Service blog.
As they say:
Using provocative and disturbing imagery as part of anti-drug advertisements might be unwarranted if it has not been demonstrated to be effective. More research needs to determine whether these kinds of advertisements are successful in preventing harmful drug use and promoting treatment-seeking behavior. Absent careful evaluation demonstrating the efficacy of prevention efforts, the potential for unintended consequences is great. Consequently, vigilance and careful evaluations are key components of effective interventions for addiction.