This might be a really stupid thing to post. If so, I will delete it. I've done a LOT of reading on this subject and want to share what I think might be causing these. I think it could be used to help others in the future. I am diagnosed with autism and with bipolar, later changed schizoaffective. I have features of both, so this is a somewhat lived experience. This is NOT medical advice or scientifically approved, as I am a layman. Another note, I used autism sp. and schizophrenia sp. to denote these two patterns of thinking, but I'm not always saying these two diagnoses in particular. If I seem like I'm losing it just let me know and I'll delete.

From what I've come to learn, autism seems to be related to underconnectivity of regions of the brain, and that causes things like social difficulties and overstimulation. While schizophrenia related illnesses are a failure of the brain to prune itself after a certain age, resulting in overconnectivity, and it causes the same difficulties, but for entirely opposite reasons. In autism, there is not enough internal and too much external activity (sensory overload), while in schizophrenia, the reverse is true. The brain in the psychotic spectrum tries to make sense of a lack of information through more internal activity, and experiences psychosis mania.

In terms of cognition, autism is implicated in "systemizing" or organizing information that comes in through the senses, which results in things like fixations and executive/task shifting difficulties. While psychosis does the opposite, breaking down the information and recreating new associations, reinforced not by external stimuli but by thought. Then results in apathy because the original "reward" circuits of the brain can't work as effectively as they did before the disorder started.

In an evolutionary sense, subtle traits of autism may have been naturally selected because high systemization led to certain survival benefits, while subtle traits of schizophrenia could've led to increased ingenuity or the generation of novel ideas. In certain "doses", both systemization and generative thought lead to the creation of complex social structures and religions, and learning allows us to integrate into our cultures starting from birth and function within/contribute to our societies. But combining these traits multiple times may increase the effect, resulting in disabilities (that statement is a huge stretch cause I only read it once).

The analogy to "autism spectrum" in schizophrenia is potentially called schizotypy, which is a stable mental trait, not a disorder. It is found at "healthy" rates in those who are creative, but also varies in those with mood disorders, psychotic disorders, some personality disorders, and many other vaguely understood areas in general. Someone with certain levels/types of schizotypy has advantageous cognitive abilities, but have mild impairment with other areas. They are capable of making strong associations between things other people could miss. They tend to make great artists, physicists, mathematicians, etc. They are also prone to making "errors", or connections or attributions that aren't there, or having subtle whimsical beliefs. They may overestimate social cues and perceive things as more significant than they are, develop odd phobias, etc. But in an over-systemizing brain (related to autism), someone misses the cues entirely because they have not been developed at the appropriate age, and have to learn them later.

Both are potentially neurodevelopmental, with some viewing conditions like schizophrenia and bipolar as such. Additionally, schizophrenia and autism seem to be the only two mental illnesses that can impair development of all areas of functioning to the extreme extent that they do, and are also the two disorders which can be extremely subtle, to the point of being misdiagnosed or not even detected, such as when these two types of disorders are misdiagnosed. In my view, it seems like autism is probably diagnosed more because the desire to systemize and sensitivity to external stimuli results in self-analysis of symptoms (with other conditions like OCD, anxieties, depression, which are all co-diagnosed with autism), while schizotypal traits tend to lower insight and awareness.

I think it would be useful to draw on people's strengths. For some people, I wonder if it would be possible to train them to use particular strengths they might not know they have. Because in my experience I've frequently been told about how I'm sick/ill more often than I've been told how good I am at certain things or how fast I can acquire certain skills. My psychosis destroyed my life before I got treatment, and both these issues are pretty awful, but my ongoing desire is to see if they can at least be used in a way that is helpful to me.