As an atheist, it's hard for me to be very interested in the devil's alleged strategies. One of the problems with Christianity (and other religions) is that people with mental illness often do not get the treatment they need, because their illness is often misdiagnosed and treated through prayer, deliverance ministries, etc. Even common mental illnesses like depression are sometimes not treated, because Christians tend to believe the devil is responsible for every misfortune.
On the other hand, some people with psychosis are comforted by their Christian beliefs. Trusting that "it is all over for the devil" reduces their fear, and this calm reduces psychosis. The ancient Egyptians had sleep temples where mental illnesses were treated using religious practices (
https://en.wikipedia.org/wiki/Sleep_temple ). Sometimes religion helps people too.
By saying this, you are showing that your understanding of the subject is found wanting. There are churches who refuse to get involved in the supernatural, preferring instead to express themselves without God's help or involvement. There are others like my church that make the supernatural central to their life and activity because we believe the bible where Jesus says that without him we can do nothing.
A few weeks ago we had a call about a young man who had been beaten by a gang, had suffered brain damage and had gone into a coma and the hospital was not confident that he would be anything other than a vegetable. We were called in and we went and laid hands on him and asked God to provide a miracle of healing. A few days ago the hospital reported that he had gained consciousness and was sitting up and talking.
We made no claim to supernatural power ourselves as we wanted and knew that the healing was the mercy of God as we obeyed his word and went and prayed for him. As the bible says without faith it is impossible to please God which means that with faith it is possible to please God.
God does not give people metal illness but he can use it for good as it says that all things can work together for good for those who love God and are called according to his purposes. That does not mean that what is happening is good, but it can work together for good in the long term.
If God does not give people a mental disorder then it has to come from Satan or the person rebelling against God. It is clear that Satan wants people to believe that he does not exist as that gives him free reign to destroy people's lives. The Bible is so true when it says that Satan is only interested in stealing, killing and destroying. He does that in myriad ways and is allowed to do that because we don't believe he exists.
However, the true believer knows that he exists so they put on the armour of God and as a result are able to stand strong against his attacks.
You make a mistake if you want God to be your GP and dispense aspirins to solve the problem. The first and most important thing is to find out God's will and that is not always as simple as ABC because he has a long term approach to our well-being and there are often factors involved that we know nothing about but which he does. We are taught by the Bible to give thanks in everything good or bad because whatever happens is the will of God for us. As has been said many times we grow in our sufferings, not our successes. This is a maxim of the business world as many rich people have gone broke on the path to riches and it is those times where they have learnt the most.
I am autistic on the high end of the spectrum and the correct diagnosis for it is that it is not a disability but a different ability. Whilst it does have its problems, I focus on its positives as it enables me to hear God and trust him without doubt as my faith is very simple and straightforward.
