Pastors have told me that mental illness is one of the worst things for the faith. I agree with them because that is largely how I lost mine.
Engaging with the supernatural and psychosis are often indistinguishable from each other. You could argue that the supernatural mainly manifests itself on the seat of consciousness. But mental illness often produces the same experiences as the supernatural purports to. Parts of bipolar mania are indistinguishable from the comforting positive experience of God most Christians promise. The voice of God often tells people to do things one wouldn’t think of had they been behaving rationally, but that same irrational voice of God is speaking loudly when someone is psychotic.
Anxiety is basically God now showing up, LOUDLY. Christians promise an experience of God which, while in anxiety, the exact opposite is produced. People who struggle with anxiety (including myself) have a hard time letting go and letting God because when we do things are even worse because our pathology is there instead of God. For us medication works worlds better than meditation. People without mental illnesses like to criticize us for this and call us weak or reprobate which pushes us further away from the faith.
God promises to never give you more than you can handle but mental illness is often the fallout of being pushed past your limit. There is this idea in Christianity that suffering is good. But mental illness seems to transpire off this map. For one every incident of psychosis weakens you so less stress is required to produce another one. For two (at least in my experience) pastors realize that because you have a mental illness you are an existential threat to the faith and treat you accordingly (and the laity simply ignore you because you don’t possess the “life gems” like money, status, and SO, etc..). Also suffering is really only ever redeemed communally while those with mental illnesses are often isolated because of vocational/social failure, stigma, and the fact that their pathology often causes them to behave in ways that push people away.
Depression produces the exact same experience as worm theology. Some Christians say you’re worse than the worst of the worst. The problem is people who struggle with depression often do their self flagellation in the name of their illness instead of the name of God. Also some Christians believe despair is a sin which is tantamount to guilting someone for being depressed. It’s like if you got a cold and instead of trying to treat it they just told you you were damned.
People with mental illness are often single and harder to engage as they get to middle age. The church is all about engaging older people as couples and doesn’t do too good of a job including older single people (those of us with mental illnesses often are not successful in the world or church’s eyes and this keeps us single). The other facet of the suffering mental illness produces not being redemptive is that when Christians help people with mental illnesses it often doesn’t feel redemptive as the pathology often causes sufferers to act in ways that confound Christians’ models of what suffering should look like. One has to be really sacrificial and a lot of times the effort put forth feels like plowing the sea. In our “me first” culture very few people are willing to go to these lengths particularly when engagement challenges their beliefs.
Mental illness kills redemptive narratives. Part of staying Christian involves cobbling together some kind of redemptive back story to try to make things make sense in hindsight (to show God somehow being involved despite everything). Mental illness, particularly depression, causes one to chafe against seeing anything redemptive about the past because suffering from it is senseless, chaotic, and often isolating suffering and when a mind has been in this state long enough it is no longer able to play the mental gymnastics needed to polish a turd.
There’s a good reason why in the Bible mental illness was always seen as direct action of the devil or his charges. Because to this day it’s destroying faiths all around.