Is it real? Well thats a bit subjective, but for the sake of the question, yes, but in two parts.
I think for the practitioner its a voluntary act, like we choose to this, i choose to have spirits in me for their guidance, i choose to look deep in myself and the spiritual planes to bring the energy forward and manifest. Those who do it in this sense, I dont see it as possession. This is voluntary and seeks a higher purpose in doing so, whatever that purpose may be, but its the magi remaining in control of the situation. So is this possession? If its by your own free will and accord that a foreign energy (or even a higher form of our own) is allowed inside and to take the wheel of our bodies, no I do not believe it is, we are in control ultimately.
The other being the involuntary possession, which is a whole different boat. As having known a few “exorcists” in the past, i feel these people were charlatans, who preyed on those spiritually weak and told them what they wanted to hear. That they had “demons” living in them, that they needed God and Jesus to save them, to repent, and accept him. I knew something was wrong in this, it felt more like a staged event, like a play, and they would force their energy to these people, making them writhe on the floor, spitting, screaming, cursing until they accepted Jesus. Unfortunately for those individuals that they had told them that they were possessed, it never goes away for them. It eats them alive, it plants a seed of fear and doubt which parasites just love to feast on. That’s what these things are, are parasites in a host that they can take over and manipulate, and the exorcist since they have no real power or understanding of higher spiritual beings sans the new testament, is like a wasps nest, full of parasites, just swarming with doubt and disease. Parasites, archons, whatever you choose to call them. These are the creatures of this type of possession. I’ve met quite a few who have said they’ve been “demonically” possessed, but all I saw were scared children being preyed upon by a snake oil salesman and his parasites. So is this possession? Yes, since they are under control of another, and do not have the ability to be in control.
Just my two cents on this topic, maybe a bit derailed.