There can also be factors in this community that make people both unusually likely to go insane and to also try things like meditation and LSD in an attempt to help themselves. It's a bit hard to say given that the post is so vague on what exactly "insanity" means, but the examples of acausal trade etc. make me suspect that it's related to a specific kind of anxiety which seems to be common in the community. 

That same kind of anxiety also made me (temporarily) go very slightly crazy many years ago, when I learned about quantum mechanics (and I had neither done psychedelics nor had I yet started meditating at the time), and it feels like the same kind of thing that causes the occasional person to freak out about Roko's Basilisk. I think those kinds of people are particularly likely to be drawn to LW, because they subconsciously see rationality as a way to try to control their anxiety [LW(p) · GW(p)], and that same thing causes them to seek out psychedelics and meditation. And then rationality, meditation, and psychedelics are all things that might also dismantle some of the existing defenses their mind has against that anxiety.

Yeah, I think people who are high in abstract thinking and believing their beliefs and anxious thought patterns should really stay away from psychedelics and from leaning too hard into their run-away thought trains. Also, try to stay grounded with people and activities that don't send you off into abstract thought space. Spend some time with calm normal people who look at the world in straightforward ways, not only creative wild thinkers. Spend time doing hobbies outdoors that use your physical body and attention in satisfying ways, keeping you engaged enough to stay out of your head.

Even if they were somehow extremely beneficial normally (which is fairly unlikely), any significant risk of going insane seems much too high. I would posit they have such a risk for exactly the same reason -when using them, you are deliberately routing around very fundamental safety features of your mind.

The MBSR studies are two-month interventions. They are not going to have the same strong effects as people meditating seriously for years. 

On the other hand, those studies that investigate people who meditate a lot are often from a monastic setting where people have teachers which is quite different from someone meditating without a teacher and orienting themselves with the Mind Illuminated.

I find it ironic that in a community that values clear thinking many people do things with their brains similar to giving their computer a hard kick or setting it on fire and expecting that to improve its performance.

It's the fucking impulsive contrarianism, isn't it? The more people keep telling you about those who have ruined their lives by taking drugs, the more certain you feel that you will do it the right way that will magically give you mental superpowers, unlike all those idiots who were simply doing it wrong. Induction is for losers. Also, you are smarter than everyone, and you did your "reseach" on internet, or asked a friend.

I wonder why these long term effects seem relatively sparsely documented.

I think the long-term effects of LSD and other drugs are documented sufficiently. It's just, if there are 100 boring statistics about people who fucked up their lives, and 1 exciting speculative book by Timothy Leary, everyone will talk about the latter.

Ah, you meant meditation. I guess the standard excuse is that people who got hurt by meditation were either doing it wrong, or they had some extremely rare pre-existing condition. (Translated: no matter how many people get hurt by doing X, it obviously does not apply to me. Because they were stupid and they were doing it wrong, and I am smart and I will be doing it right. Also, they were weak, and I am invulnerable.) The same excuse applies to people who join an MLM pyramid scheme and lose their money, or people who pray to God to cure their sick child and then the child dies anyway. The theory is always correct; if it doesn't work for you, you were clearly applying it incorrectly.

How many more people have to die, before we learn the thing that a random 10 years old kid could tell us?

If I'd go towards making the recommendations vs guidelines, and following the law of equal and opposite advice, I'd do the following:

Notice subtle things in yourself, unless you tend to jump to conclusions.

Keep doing the best thing, even if you don't have a legible story for why it's good. But beware illegible impact, as it's very easy to be overoptimistic and illegible impact can't be held to account since it can't be verified by somebody not themselves, thus groups above a certain size should enforce legible impact to keep things honest and not fall prey to overoptimism.

Don't go insane, but don't overworry about insanity. A healthy environment is prevention enough.

Reject false dichotomies... as soon as it comes clear that they are false dichotomies. Until then, you may entertain both options (maybe weighted by independent evidence).

Research advice (consider the Advice Repositories), but avoid Analysis Paralysis.

More the second one. Plus runaway anxiety spirals and depression.

Also, realizing that it all adds up to normality [? · GW]. Learning about quantum physics, or decision theory, or the mind being made of sub-agents, should not make you do crazy things. Your map has changed, but the territory remains the same as it was yesterday. If your sub-agents were able to create a sane individual yesterday, it should be achievable today and tomorrow, too.

This is not necessarily the case. Means may be different from medians may be different from tails, various populations might be at higher risk, rare downsides might be large enough to make up for their rarity, etc.

"One guy has presented evidence that I won't even link, so this post should be weakened" is not a sound principle, either.