"The demon enters, it is true, as a squatter and not as an owner or a guest or one who has a right to be there. He comes in as an intruder and as an invader and enemy. But come he does if the door is opened by serious and protracted sin."
—Merrill F. Unger
Satan hates you and has a terrible plan for your life. If he cannot succeed in robbing you of eternal life, he will do everything in his power to deprive you of the joy, influence, and rewards that come from serving God in this life. Since Satan cannot be in more than one place at a time, he has delegated much of his work to demons who discourage distract, and deceive through a variety of means.
Since Satan is referred to as "the ruler of this world" (John 12:31) and "the prince of the power of the air" (Ephesians 2:2), it is reasonable to assume that he and his demons have some control over the elements of nature such as wind, rain, hurricanes, and tornadoes. Living in a city that was almost leveled by a tornado, I can assure you that nothing is more discouraging to Christians than seeing their homes and possessions completely destroyed in an instant. Remember that it was Satan (or one of his "wind demons") who directed a "great wind" to collapse the home of Job's oldest son, resulting in the deaths of all Job's children (Job 1:19).
To blame every illness on demonic activity is neither logical nor biblical. Some of our illnesses are the result of our inhabiting sin-infected bodies. Because our bodies have inherited Adam's curse, we contract illnesses and die. Other times, our diseases are precipitated by poor lifestyle choices: too many trips to McDonald's, too few trips to the gym, or hurtful addictions to things such as alcohol, nicotine, drugs, or Haagen-Dazs vanilla ice cream (now you know mine).
Though not all illnesses are caused by Satan and his demons, some of them are. In describing Jesus' ministry of healing, the gospel writers distinguished between sicknesses that were caused by demons and those that were not.
When evening came, after the sun had set, they began bringing to Him all who were ill and those who were demon-possessed...And He healed many who were ill with various diseases, and cast out many demons (Mark 1:32,34).
If every illness had been caused by demons, Mark would have recorded that the people were bringing to Jesus all who were demon-possessed instead of those "who were ill and those who were demon-possessed." Obviously, Mark is telling us there were some people who were physically sick but not under demonic influence.
Through Mental Disorders
Again, it is a mistake to say that all mental illness is directly attributable to demons. When I asked a Christian psychiatrist about the relationship between mental illness and demonic activity, she responded with her own question: "If mental disorders are the result of demonic activity, then why do the symptoms almost always disappear when treated with the right drugs?" Good question.
Our thoughts and emotions are directly traceable to a series of electrical and chemical impulses in the brain. When the brain does not function properly, drug therapy can help restore the natural balances that God intended. However, our thoughts and emotions are more than a series of electrical and chemical impulses. There's an immeasurable, though very real, spiritual component that influences our thoughts and emotions. Positively, this spiritual component can protect us from anxiety and its attendant consequences: "Be anxious for nothing, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all comprehension, will guard your hearts and your minds in Christ Jesus" (Philippians 4:6-7).
We will discuss how to apply this passage in a later chapter; my point here is that if a positive spiritual exercise like prayer can influence our thought processes by removing anxiety, then it is reasonable to conclude there are also negative spiritual influences that can seize control of our minds and emotions. While not all mental disorders are caused by external spiritual forces such as demons, some of them are.
Consider the man in Luke 8 who was controlled by numerous demons. A refusal to put on clothes, withdrawal from others, strange voices emanating from his mouth, and deep depression were symptoms that today would immediately land him in a mental hospital. Yet as soon as the demons left him, notice the immediate and radical change in his mental state and behavior: "The people went out to see what had happened; and they came to Jesus, and found the man from whom the demons had gone out, sitting down at the feet of Jesus, clothed and in his right mind; and they became frightened. Those who had seen it reported to them how the man who was demon-possessed had been made well" (Luke 8:35-36).
The restoration of this man's mental health did not require years of psychotherapy or drug treatment, because his root problem was not primarily physical or emotional, but spiritual. Please understand that I'm not condemning psychotherapy or chemical treatment. Strong biblical counsel and appropriate drug therapy are tools God can use to bring emotional healing to people. What I am suggesting is that sometimes there is also a spiritual component to mental disorders we should not ignore.
Through Other People
Demons can use other people to discourage, distract, and deceive us. In extreme instances, demons have the ability to use human agents to persecute and murder other Christians. John attributes the slaughter of God's people during the coming Great Tribulation to demonic activity (see Revelation 18:2,24). We have witnessed similar persecution throughout history and in many areas of the world today.
What Can You Do?
While no Christian can be possessed by a demon, we can be influenced by demons. Any area of our lives that is not controlled by the Holy Spirit is vulnerable to being controlled by Satan and his forces. You may remember from physics that nature abhors a vacuum. The same truth applies to the spiritual realm. Some spiritual force is going to fill or control your life. Any area of your existence — finances, marriage, work, and morality — that is not being directed by the Holy Spirit is vulnerable to being controlled by demonic influences.
The key to resisting demonic influences in our lives is to make sure that every area of our lives is filled or controlled by God.
(Adapted from The Divine Defense by Robert Jeffress, Waterbrook Press, 2006)