Is it possible? I some some forum posts on another website and people were all hush hush when I asked them.
I actually have thought about this in the past and will probably attempt it as I move along in the future. Your best bet is to evoke an entity inn a dream to teach you how to use your dreams for this or any other purpose. (Sandman?)
haven’t ever done anything like this - but from what I do know, and have done in dream work, you would simply plant an idea (an accident, cancer, MS, advanced diabetic problems, etc.) deep into their subconscious as a seed-thought. Dress it in such a way that they think it’s from their own mind by surrounding it with information that you know about them. For instance, if they smoke, the seed thought is “I’m going to get cancer from smoking”. Symbolically plant it in the fertile part of the garden of their mind. Make sure it’s a strong seed - amp it up with a lot of energy and protection against their own thought immune defense systems. You might even look for an actual garden that is fertile in their mind and literally plant a seed. Put protective defenses around it - perhaps even write the defenses to appear to be defenses that they have constructed themselves, such as “I deserve this because I’m a bad person” or “if I get cancer, it’s my own fault”.
I bet you’d see extremely fast results.