Question: how do we know people are being possessed and it's not a trick of the mind? After all people in ancient times likely thought diseases, mental illness and sleep paralysis were caused by demons/bad spirits too, not to mention instances where people think something's physically wrong and they feel symptoms like a reverse placebo effect even though nothing's physically wrong. If they actually are demons, why hasn't the scientific community cracked down on them to understand them and where they come from (after all if certain things stir them they should easily be able to be scientifically measured and detected)? Why haven't many regular people cracked down on them? Why isn't anyone ever educated about it like protecting yourself from diseases or physical assault or anything like that?
In the 60's, 70's and 80's drugs like cannabis were natural herbs that people used for recreational purposes, Acid and Cocaine was used to much lesser degree. Since the 90 to present day, people have sought to make drugs more potent and mind altering, growing them artificially with added chemicals, this leads to much more people being susceptible to mental illness, hearing voices, doing harder drugs, (cut with dangerous chemicals), prescription meds, then and or throw in alcohol into the mix and you have a disaster on your hands.
Take any of the above; drugs with alcohol and interest in the occult, and you have the potential to invite unwanted spirits into your life. Not all occult practices are presented as dark and evil, some are packaged to appeal to lonely or even adventurous people. The problem is opening that portal into the unseen can have lasting implications and effects, and the remedy if done properly takes 7-10 days usually requires outside intervention, because rarely will a Spirit just sit there and let you start inflicting pain on it without a fightback. If left long enough the Spirit will have the ability to flow in your veins, mimic your voice, so when you find yourself thinking something that you can't usually relate to, then likely it's the spirit trying to influence your thoughts.
The worst forms of possession come from people that you know paying someone to target you. That will involve them knowing personal details and having an item belonging to you. There are whole communities in Africa, Asia and South America dedicated to summoning spirits against people for a fee. It is less common place in the West, but there are dark practitioners. Some amongst the elite in the West also have the ability to summon spirits, but they usually do so for their own personal gain; wealth, power and women etc
You can also come into contact with weaker Spirits without even knowing it, but these are usually content with just being able to take you away from the remembrance of GOD.
Every culture and Religion has their own way of evaluating if it's a genuine case of possession or mental illness.
Not wanting to break any forum rules; I will briefly outline how it is diagnosed in my faith, Islam:
It involves a diy test that takes 30-40 mins for adults.
If you have children that spend ages watching junk then you can do a 2 min test on them whilst they're asleep and watch the results before your eyes. It can be scary though, so not for the faint of heart.
Peace out and don't let the bed bugs bite!