I find very helpful the comments of those people who are reminding people, or pointing it out for the first time, things like taking medication may easily help, but it certainly doesn't mean the person wasn't demonically possessed.
I suppose that evil forces have a concerted interest in making science seem true. You'd be very, very, very, very (etc.) surprised at just how quick (beyond speed) and how opportunistically at any point of meaning or even possible meaning that evil forces make actions. And so it's also quite disconcerting to me to see people hold up science as a "be all and end all". Like the person above on this page who said that there is no demonic possession because science can't prove it.
Science can't prove or explain anything that is part of the spirit world. It just will never be able to do. Any scientist will tell you that now - that spiritual existence is nothing to do with science. Can scientific theories explain love? Of course not. They never, ever will. People are spirits. That's always more than the examinable make up and "ticking over-ness" of their bodies, and also, bodies are also far, far, far from only this scientific physically explicable thing alone.
It can be easy to fall into a rut if you have not been thinking cautiously for some time or during a lot of your life (& very easy to be oblivious to your mistake), to assume something. That is that this world is all known, quantified or quantifiable into mathematical or scientific type explanations and everything can be explained. That's nuts. I have done it when I was younger - thinking that beings are spirits but the physical world can always be explained (or maybe there will be, hardly ever, some exceptions that are inexplicable).
Beings are spirits that are, at least originally, part of the genius of god which is so amazing there is no explanation. How can there be an explanation if there can't be any questions formulated? It's beyond reason, beyond calculations, beyond formulae. Spirits are in existence reasonless, part of kind of super bright light genius beyond and below genius because there is no meaning but the light of god.