A common and surprisingly enough, not very startling symptom of certain mental states, including certain drug influenced states, is the belief that events happening in the present are affecting events happening in the past. I first heard of this in the infamous DXM FAQ.
8.2.7 Memory Loops and Prescient Sensations
DXM can severely alter the sense of causality, and with upper plateau and Plateau Sigma trips, one can lose one's sense of causality completely. One person reported a sudden feeling that he was contacting his own mind in the past, passing to himself the ideas and insights he had experienced as a child. Another person felt such a strong sense of deja vu, coupled with memory impairment, that he believed he'd had a prescient dream of the current events. Such occurrances are probably a consequence of the profound alterations of memory and recognition networks. It's hard to describe how utterly convincing these sensations can seem while under the influence of dissociatives.
Thinking this a rather trippy idea, I suggested the idea that I was talking to my young self while in a hypnotic state. It seemed fairly believable to me at the time, although under hypnosis I also managed to convince myself that I was a lord of Gondolin.
There followed a month or two period in which I spent my time walking around the hills of Montana, slightly confused as to which was my past and which was my future. It was pretty interesting. This was all sans any drugs besides strong doses of adenosine antagonists.
Reverse casuality can probably be accounted for the way that a great deal of other dissassociative phenomena can be, by a cut in communications between the limbic system and the cerebral cortext. In theory, the limbic system stores a great deal of environmental variables, such as normal temporal and spatial concepts. The limbic system tells people when it is time to go to bed, when it is time to take a bath and when it is time to mate. The cerebral cortext on the other hand, is built for abstract thought, and its various lobes can think about anything, including the square root of green. When it is not constantly bothered by input about bathing and eating, it will hypercognisize, thinking up such things as different ways the various pieces of time and space could fit together. Drugs that disrupt the limbibc system's functioning, or else just discplined subsuming of the limbic system to the cerebral cortext, can accomplish this.