Ambien has been reported to cause sleepwalking, as well as driving, cooking and eating while asleep. Were these really manifestations of spirit possession activity? If so, was this a consequence of increased susceptibility to manipulation by spirits already on board, or does the drug increase vulnerability to becoming spirit possessed or both?

Both things are true. When people are carrying out actions without conscious awareness, this is being done by another consciousness seeking to control the body. The movement of the body is a conscious act of volition. In the absence of conscious control, movement will not happen other than through reflexes being triggered. This is why someone who is concussed will not carry on any physical activity in the absence of awareness, but the body will shut down entirely until consciousness returns. When consciousness is blocked chemically, there is the opportunity for something to happen, and when the block is not done in the normal way, it is easier for the interlopers to take over the reins. During the normal sleep process, there is a mechanism to keep the body in a quiescent mode, so it is not simple for the spirit meddlers to make the body do things. What they take advantage of with the sleepwalker is a stage of sleep that is very, very light. If an individual can go into that level and maintain it as a kind of characteristic of how their mind works, they will be more vulnerable to manipulation, because in that particular level of conscious functioning, the body will be operable if instructions are relayed. This gives the spirits an in, so to speak, and they can begin to make things happen. That is what the drug does, it shuts down conscious awareness, but not so deeply that the body cannot be aroused if there is a consciousness to do so, and this allows the spirits a chance to have some fun.