How can we decide if there is demonic involvement in a particular situation? Some would attribute every illness and sin to demonic influence. But Scripture lists demonic involvement as only one of the things Jesus dealt with (Matthew 4:24) and gives the primary source of sin as our own desires (James 1:14,15) Others would minimize or deny it, particularly in the life of a believer. (This largely comes from the King James use of the word "possession," which has no basis in the Greek.) There is also the spiritual gift of discernment of spirits, which I believe still exists today and I claim to possess. But the problem with this gift is you need to start by deciding if the gift involved is real. I know of an individual who once thought they had the gift and later decided it was spurious. What is the correct approach?
There are lists of signs of demonic involvement. But while some items come from Scripture, most come from experience, tradition, or even Hollywood. While Scripture mentions blatantly supernatural cases (Mark 5:2-20) (and these may sometimes be faked), often the symptoms are those of normal illness (Matthew 12:22). The fact that Scripture does not give a list suggests that knowing the source of the problem may not always be necessary. We need to pray for our and other's problems no matter what source they come from (Ephesians 6:18). It is also important to have other people pray for you (James 5:14-18). If there is something that suggests there might be demonic activity, it is worthwhile to direct your prayers against such activity.
I remember a sin in my life that I could not get the victory over. I asked someone to pray for me specifically against demonic involvement. I really was not expecting much, but I thought I would try one more approach. He had trouble praying and could not get his thoughts together. I had a huge feeling of weakness come over me and could not stay standing and fell down to my knees. It did not immediately solve all my sin problem. But it was the first step to turning the situation around. I remember another case where I was driving to help out in a particular situation and I could not find the house. I stopped driving to look at the map and could not read the map; it was blurred (this was totally abnormal for the state of my vision at the time). I immediately became suspicious and prayed God would lead me to the house. My vision cleared, I read the map and drove directly there. Every case needs to be dealt with based on the factors involved. Nor should we neglect to make use of appropriate medical assistance if the problem persists. But since Scripture does not give a formula for dealing with these situations, they should be approached carefully, with prayer and trust in God.