Schizophrenia is defined as a serious mental disorder in which people interpret reality abnormally. According to the Mayo Clinic, it's not known what causes schizophrenia; but researchers believe that a combination of genetics, brain chemistry, and environment contributes to development of the disorder. Symptoms include delusions, hallucinations such as hearing voices or seeing things that are not there, disorganized thinking and speech, disorganized and abnormal motor behavior, and reduced or lack of ability to function normally. Interestingly, children and older adults are rarely diagnosed with symptoms. They are predominantly seen in young adults in their 20s and 30s. As with other mental disorders, some possible causes have to do with early trauma such as having a family history of schizophrenia, some pregnancy and birth complications, and taking mind-altering (psychoactive or psychotropic) drugs during teen years and young adulthood. Also, like other mental disorders, the scientific and medical communities deal with the physical aspects such as brain chemistry while Christians tend to look at the spiritual side as well. Not all mental disorders are demonic but, some can be related to demonic activity (Mt 4:24).
Sometimes the spiritual and natural overlap and have parallels. There is a spiritual parallel to schizophrenia, and it can affect both those who profess to be Christians and those who do not. One symptom with parallels is delusion. That is defined as a false belief or judgment about external reality, held despite incontrovertible evidence to the contrary. Some people hold to the delusion that there is no God no matter what evidence they are presented with (Ps 14:1). Atheist Richard Dawkins infamously published his book entitled, "The God Delusion". Sadly, it is he who is under delusion. This delusion is self-imposed because God has seen to it that everyone has enough clear evidence to believe in Him so that they are without excuse (Rom 1:18-32, Rom 2). Because of that, the atheist is more accurately described as a denier. When people adamantly reject the truth of God after He has tried to lead them into it, He will send them a delusion of His choosing (Is 66:4, 2Thes 2, esp. vs 11). This can include false doctrine, belief in the antichrist, and atheism. God gives everyone ample opportunity, but He gave us choice (2Pet 3:9). This is especially fearful for those who claim to be believers. There is no greater danger than thinking you believe the truth when you do not. This includes false versions of Christianity which Jesus and the apostles did not initiate nor endorse (Mt 24:4-5 & 11 & 23-28, Gal 1:6-9, 2Pet 2, etc.).
Another symptom of spiritual schizophrenia is hallucinations. It may seem strange to associate hallucinations with people who call themselves Christians, but this happens all the time. They claim to hear from God no matter how divergent what they are hearing is from the Bible. The other extreme response to this is to claim that God no longer speaks to people directly and only speaks through the scriptures. There should be no doubt that every spiritual experience we claim to have must pass Biblical muster, and the scriptures are the primary voice of God for us today. However, God certainly still speaks to people. God spoke to people before the first scriptures were written. He spoke to people while the scriptures were being written, and there is no Biblical or other sound reason to conclude that He no longer communicates with man except through the Bible. Preaching and spiritual gifts are just two examples. There is definitely a lot of bogus activity flying under the banner of "God told me, I feel, I heard a voice, etc."; but we should not throw out the baby with the bath water. Paul and John told us to test these things, not to assert that they no longer happen (1Cor 14:29-32, 1Jn 4:1-3). The same principle applies to dreams and visions (Joel 2:28, Acts 2:17). Some dreams are from God. Some are from our own minds. Some are from late night pizza. Church leadership and the spiritually mature are to help people discern which is which following Biblical principles and precedents. True witnesses are to speak what they see and hear (Deut 5:24, Mt 11:4, Lk 2:20, Jn 3:32, Acts 4:20, Acts 22:15, 1Jn 1:1-3, Rev 22:8). However, it is a fearful thing to bear false witness (Prov 6:19, Prov 19:5, Prov 21:28). We should be very careful about claiming to have heard from God or to have seen things (Deut 13:1-5, Deut 18:18-22, Eze 13. etc.).
Falsely hearing and seeing includes falsely interpreting scripture. The word exegesis means to bring out the meaning of scripture. The word eisegesis means to insert a meaning into the scripture. There is much eisegesis taking place today, and there are many examples of it. It is our duty to know the Lord and the scriptures for ourselves so we can discern when this is happening. When people assert things that are not in the Bible are there, you can start by asking what scripture that is. This might sound overly simple, but it is essential to read what is actually there and not what we think or what people say is there. Don't just assume something is in the Bible or that their interpretation is correct just because they say so. It does not matter how authoritative or how famous the person is. It doesn't even matter how many miracles they perform (Deut 13:1-5, Mt 7:21-29, Mt 24:24, Gal 1:6-9, 2Thes 2:9-12, Rev 13:11-15, Rev 19:20). God is doing miracles all over the world every day, but miracles are not the measure of sound doctrine. The Bible is. It is eternally dangerous to tamper with the scriptures and their interpretation (Deut 4:2, Prov 30: 5-6, Gal 1:6-9, Rev 22:18-19).
They say that imitation is the highest form of flattery. Coca Cola used to have the motto, "It's the real thing". The obvious implication is that all the other soft drinks are just imitations of it. The best the devil can do is merely an imitation of what God does. There have always been imposters and imitators. This is nothing new, and we should not be surprised (2Cor 11:13-15). This includes doctrine, ministry, and spiritual gifts. Some people have grossly misrepresented the operation of spiritual gifts. This has turned some people off to the whole concept, confused others, and led many astray from the "real thing". The spiritual gifts Paul wrote about in 1Corinthians 12-14 are very real and still active. Some people are sincere but getting it wrong. Others are false prophets out to mislead. They are claiming to experience, and to lead others to experience, things that have nothing to do with God. They display "disorganized thinking and speech, disorganized and abnormal motor behavior, and reduced or lack of ability to function normally". Sometimes it is so obvious that even people who have never received the baptism of the Holy Ghost with the initial outward evidence of speaking in tongues like they did in the book of Acts (2:4, 10:43-48, 19:1-7) can see how phony it is. This is just a confirmation of what Jesus and the apostles warned us about. It is a manifestation of spiritual schizophrenia. Yet again, we must not throw out the baby with the bath water. There is also plenty of real supernatural power of the Holy Ghost for us, and God is not on a Sabbatical.
As with natural schizophrenia, spiritual schizophrenia seems to target young adults, although not exclusively. There are megachurches and other groups that are specifically targeting young adults with schizophrenic versions of Christianity. They use things like "cultural relevance", pop style music, a concert/entertainment atmosphere, and doctrine that scratches itching ears rather than bringing life-changing conviction and life-long commitment (2Tim 4:1-4). People who seem to be more vulnerable are people who did not have a strong, 2-parent, Christian upbringing. Spiritual damage suffered in childhood is a recipe for spiritual dysfunction in adulthood, although God is greater than all of that.
We must have balance, sound understanding of the scriptures, and a relationship with the Lord that helps us know what is real and what is not, and what is correct and what is not (Jn 10:1-16). God can cause us to overcome anything that is not of Him when we follow Him and His word. It is challenging to navigate the waters of everything the world throws at us, but there is eternal blessing for the overcomer.