A great article from SimplyHeavenlyFood about the demons and their influence on humans:
The Bible gives some examples of people possessed or influenced by demons. From these examples we can find some symptoms of demonic influence and gain insight as to how a demon possesses someone. Here are some of the biblical passages: Matthew 9:32-33; 12:22; 17:18; Mark 5:1-20; 7:26-30; Luke 4:33-36; Luke 22:3; Acts 16:16-18. In some of these passages, the demon possession causes physical ailments such as inability to speak, epileptic symptoms, blindness, etc. In other cases, it causes the individual to do evil, Judas being the main example. In Acts 16:16-18, the spirit apparently gives a slave girl some ability to know things beyond her own learning. The demon-possessed man of the Gadarenes, who was possessed by a multitude of demons (Legion), had superhuman strength and lived naked among the tombstones. King Saul, after rebelling against the LORD, was troubled by an evil spirit (1 Samuel 16:14-15; 18:10-11; 19:9-10) with the apparent effect of a depressed mood and an increased desire to kill David.
Thus, there is a wide variety of possible symptoms of demon possession, such as a physical impairment that cannot be attributed to an actual physiological problem, a personality change such as depression or aggression, supernatural strength, immodesty, antisocial behavior, and perhaps the ability to share information that one has no natural way of knowing. It is important to note that nearly all, if not all, of these characteristics may have other explanations, so it is important not to label every depressed person or epileptic individual as demon-possessed. On the other hand, western cultures probably do not take satanic involvement in people’s lives seriously enough.
In addition to these physical or emotional distinctions, one can also look at spiritual attributes showing demonic influence. These may include a refusal to forgive (2 Corinthians 2:10-11) and the belief in and spread of false doctrine, especially concerning Jesus Christ and His atoning work (2 Corinthians 11:3-4, 13-15; 1 Timothy 4:1-5; 1 John 4:1-3).
Concerning the involvement of demons in the lives of Christians, the apostle Peter is an illustration of the fact that a believer can be influenced by the devil (Matthew 16:23). Some refer to Christians who are under a strong demonic influence as being “demonized,” but never is there an example in Scripture of a believer in Christ being possessed by a demon. Most theologians believe that a Christian cannot be possessed because he has the Holy Spirit abiding within (2 Corinthians 1:22; 5:5;1 Corinthians 6:19), and the Spirit of God would not share residence with a demon.
We are not told exactly how one opens himself up for possession. If Judas’ case is representative, he opened his heart to evil—in his case by his greed (John 12:6). So it may be possible that if one allows his heart to be ruled by some habitual sin, it becomes an invitation for a demon to enter. From missionaries’ experiences, demon possession also seems to be related to the worship of heathen idols and the possession of occult materials. Scripture repeatedly relates idol worship to the actual worship of demons (Leviticus 17:7; Deuteronomy 32:17; Psalm 106:37; 1 Corinthians 10:20), so it should not be surprising that involvement with idolatry could lead to demon possession.
Based on the above scriptural passages and some of the experiences of missionaries, we can conclude that many people open their lives up to demon involvement through the embracing of some sin or through cultic involvement (either knowingly or unknowingly). Examples may include immorality, drug/alcohol abuse that alters one’s state of consciousness, rebellion, bitterness, and transcendental meditation.
There is an additional consideration. Satan and his evil host can do nothing the Lord does not allow them to do (Job 1-2). This being the case, Satan, thinking he is accomplishing his own purposes, is actually accomplishing God’s good purposes, as in the case of Judas’ betrayal. Some people develop an unhealthy fascination with the occult and demonic activity. This is unwise and unbiblical. If we pursue God, if we are clothing ourselves with His armor and relying upon His strength (Ephesians 6:10-18), we have nothing to fear from the evil ones, for God rules over all! God bless you! <3
A great article from SimplyHeavenlyFood about the existence of demons:
Is there such a thing as ghosts? The answer to this question depends on what precisely is meant by the term “ghosts.” If the term means “spirit beings,” the answer is a qualified “yes.” If the term means “spirits of people who have died,” the answer is “no.” The Bible makes it abundantly clear that there are spirit beings, both good and evil. But the Bible negates the idea that the spirits of deceased human beings can remain on earth and “haunt” the living.
Hebrews 9:27 declares, “Man is destined to die once, and after that to face judgment.” That is what happens to a person’s soul-spirit after death—judgment. The result of this judgment is heaven for the believer (2 Corinthians 5:6-8; Philippians 1:23) and hell for the unbeliever (Matthew 25:46; Luke 16:22-24). There is no in-between. There is no possibility of remaining on earth in spirit form as a “ghost.” If there are such things as ghosts, according to the Bible, they absolutely cannot be the disembodied spirits of deceased human beings.
The Bible teaches very clearly that there are indeed spirit beings who can connect with and appear in our physical world. The Bible identifies these beings as angels and demons. Angels are spirit beings who are faithful in serving God. Angels are righteous, good, and holy. Demons are fallen angels, angels who rebelled against God. Demons are evil, deceptive, and destructive. According to 2 Corinthians 11:14-15, demons masquerade as “angels of light” and as “servants of righteousness.” Appearing as a “ghost” and impersonating a deceased human being definitely seem to be within the power and abilities that demons possess.
The closest biblical example of a “haunting” is found in Mark 5:1-20. A legion of demons possessed a man and used the man to haunt a graveyard. There were no ghosts involved. It was a case of a normal person being controlled by demons to terrorize the people of that area. Demons only seek to “kill, steal, and destroy” (John 10:10). They will do anything within their power to deceive people, to lead people away from God. This is very likely the explanation of “ghostly” activity today. Whether it is called a ghost, a ghoul, or a poltergeist, if there is genuine evil spiritual activity occurring, it is the work of demons.
What about instances in which “ghosts” act in “positive” ways? What about psychics who claim to summon the deceased and gain true and useful information from them? Again, it is crucial to remember that the goal of demons is to deceive. If the result is that people trust in a psychic instead of God, a demon will be more than willing to reveal true information. Even good and true information, if from a source with evil motives, can be used to mislead, corrupt, and destroy.
Interest in the paranormal is becoming increasingly common. There are individuals and businesses that claim to be “ghost-hunters,” who for a price will rid your home of ghosts. Psychics, séances, tarot cards, and mediums are increasingly considered normal. Human beings are innately aware of the spiritual world. Sadly, instead of seeking the truth about the spirit world by communing with God and studying His Word, many people allow themselves to be led astray by the spirit world. The demons surely laugh at the spiritual mass-deception that exists in the world today. God bless you! <3