http://skepdic.com/ufos_ets.html
On the other hand, those folks who believe they have been abducted have had measurable, psychologically traumatizing experiences. Are they real or hallucinations or the result of brain chemistry (something produced in the brain that behaves like dimethyltryptamine)? Are they visions or dreams? Are the creatures phantasms, or real beings...alien or demon?
I, of course, don't know.
But I do know that these people believe something happened to them. In some cases there is corroborative testimony from others of specific events and, overall, there is corroborative testimony of similar experiences.
The question is what is it?