When I looked into these things many, many moons ago I took a good long look at the abduction phenomenon. Very long story short, this is what I ended up concluding:
While a good chunk of the UFO world - including abduction stories - is highly suspect as it revolves around people saying something like: "Aliens abducted me and told me the Truth, please buy my book/DVD/whatever." - i.e. they were in it for the money - this did not apply to all. Many accounts were by people who either gained nothing from telling, even lost a lot by it, and seemed sincere about their ordeals.
Two books then opened my eyes about this further. The first was The Fairy-Faith in Celtic Countries by renowned anthropologist W. Y. Evans-Wentz from around 1900. The second was Rick Strassman's DMT: The Spirit Molecule. The first book proved that this phenomenon is way older than the 1950/60s. Evans-Wentz records tales from remote areas of Scotland, Wales, Ireland and other places that when stripped down tell stories of abductions by non-human entities (usually called "elves" or "fair people" or some such), changelings, strange lights at night, underground palaces (bases), even "men in black" who come at night in shiny stage coaches to warn off people who have encountered something. All from before the age of flight - let alone flying saucers. The second is about experiments in a closed, hospital environment, under constant supervision, of the effects of the DMT molecule on people. About half encountered some sort of contact with "non-human" entities. One, in particular, told of how he was raped by two crocodile like entities. Now, of course, no physical trauma was evident, as he was under constant supervision, but the nature of DMT and how it is "more real than reality" meant that the mental trauma was just as real.
Now, take three key elements of modern abduction stories that seem to be constant and much talked about. First, is that it runs in families. Often it is explained away as multi-generational experimentation or biological enhancement (creating hybrid species or such). Second is that it seems to favour certain groups over others, most notably people who are in security fields, such as police or military. Third, the encounters are not uniform over their lives, but come at certain times, usually in early childhood (ages 5-8 or so), around puberty (12-16), then mid life (40 or so). What does this possibly say? The occupational fields are both very often hereditary (that is, the children often enter the same occupational field as their parents), but also high stress. The ages are also high stress periods (first around the end of carefree childhood and start of school, then puberty and teen years, then mid-life crises).
What if, we are looking at a hereditary predisposition to the release of DMT under periods of high stress? This results in hallucinations that are "more real than real" and usually involve non-human entities. Take further two additional points - first is Jacques Vallee's analysis of UFO encounters over each 24 hour period, and the fact that they seem to always peak at around 3 AM in every time zone, and Rick Strasmann's view that DMT may be connected to the release of melatonin - a molecule that is released by the body during sleep and reaches a high point at around 3 AM.
What you get is a very compelling argument that one cause of abduction stories is a genetic disorder. Now, two very important elements to add at the end. First is that we still don't know exactly what happens when we are under the effects of hallucinogens. Many claim that they are not figments of our imagination but that we are transported to other "real" realms. I'd say the book is open as to what happens - we still simply do not know enough. Second, even if these are "just" genetically induced hallucinations, does not negate the negative effects that these encounters have on the people who have them. They experience them just as "real" as the real world events.
Well, that's my two cents on this.
I didn't know the human body had the capability to produce DMT, that only plants could do that