The importance of specific health communication

Often people speak in general terms about the negative effects of smoking. Here's a highly specific risk: smoking at the time of breast surgery can cause nipples to fall off. When the doctor warned his patient in general terms, she didn't really listen. When he told her specifically that her nipples might fall off if she kept smoking, she said she had the motivation to stop right away. That's a very important lesson for health communication in general, but also hard to implement because when public health campaigns do show very specific things that can go wrong, there can be accusations of scare tactics, whether it's showing very specific problems from STIs or very specific problems from smoking.

What's the line between a scare tactic and effective communication?