Off-hand? Algorithm driven social media, “news” media generally, politicians, family/kids. The last is at least usually tolerable, or at least correctable. The rest should be taken only in moderation with a mound full of salt.
Idk what your society or definition of "insanity" is but assuming you're asking what we believe most commonly leads to one's mental health entering a negative feedback loop:
Broadly speaking it's some form of hopeless desperation (yes, the hopeless qualifier matters here) that commonly kicks into high gear after falling into homelessness, at least based on my own observations
Some also get to play on hard mode simply for winning the genetic and/or socio-economic anti-lottery
These are chemicals found in every single human, how can you think they cause insanity? Also environmental stressors play a big role on mental health issues, but what you call "insanity" might be better defined as neurotransmitter imbalance, and it has not a lot to do with sex hormones, but a totally different set of chemicals.
Lack of mental stimulation ( I would also add sence of acomplishment to go with that mental stimulation.) People like to solve problem and feel good about solving those problems. When you have nothing to engage your brain it turns to other things even when those things arnt real. If you do do things with your brain but you never get any reward for it you tend to look for more extream things.
What are you talking about. We live in an era where stimulation is not only free, but fed to us with scientifically optimized algorithms. Our culture is one of stimulation addiction.