The power of suggestion is both dismissed and held in awe by humans, who claim it might be able to affect other weak minded individuals, but certainly not themselves. The media presents hypnosis as being able to cause individuals selected at random from an audience to make complete fools of themselves in front of the world, clucking like chickens and attempting to peck at seed, for instance. Likewise, the media shows hypnotized individuals, like human time bombs, walking about in human society in a normal manner, but set to explode into action when a key word is spoken or a visual picture presented.
Hypnosis, of the power of suggestion, does not work in this manner, as in all cases the individual must be in full compliance. One cannot be hypnotized to do what one does not want to do, although the suggestion can certainly be presented during hypnosis. Hypnosis encourages the conscious to relax its hold, allowing the subconscious to communicate. Any suggestions made to an individual are, perforce, being made to the subconscious, which is the solid common sense arena and processes suggestions rather than blindly accepting them. Hypnosis is used to get past the rigidities and denial imposed by the conscious, to place the conscious by the side where it can be an observer and become better integrated as a result of the discussions.
That said, how does voodoo work, as indeed it does.
Voodoo relies on the victim's belief systems, as without this no magic exists. Someone who had never heard the myths, subjected to all the incantations and pointing fingers and objects stolen or placed in one's personal quarters, would merely scratch their head. What's with them, they would wonder. On the other hand, humans raised in these cultures are impressed with the belief that voodoo works, palpable fear in the voices of the elders relaying the many tales. Spells cast upon humans thus primed to react set in motion a cycle of fear that can indeed kill. Fear can stop the heart by constricting arteries leading to the heart, or can drive the blood pressure to a point where blow-outs occur. Cast a spell and the ashen victim is found dead in their quarters the next day. Such a cooperative victim!