I think it's more a question of dose. If you're meditating 20 minutes a day for three years you probably won't see a big effect. If you're meditating 12 hours for a day for 10 years, you're going to encounter a lot of stuff that could get labeled "psychosis" by people who don't know about it. And, it may be permanent. What kind of meditation you're doing will affect what you encounter and how you deal with it, but none of the paths will remain just "a practical way to reground [your]self."
If you eat one cube of sugar in a coffee per day and no sweets you are good. If you eat one kilo of sugar each day you'll probably get diabetes in a few months.
I think the picture is a little more complicated than that. There have been entire monasteries full of people who spend many hours a day meditating for thousands of years. They don't seem to be mentally unhealthy on the whole, though there are some exceptions. So it's evidently not the kind of thing where a continuous overdose will leave your mind or your body disabled; on the contrary, the meditators tend to live longer than average and be happier.
However, the kind of experiences described (seeing visions, losing interest in mundane matters, becoming certain of beliefs that turn out to be false) are a well-known feature of the process. And it's at least widely believed that guidance from experienced meditators is very helpful, if not crucial, to navigating these experiences.
> There have been entire monasteries full of people who spend many hours a day meditating for thousands of years. They don't seem to be mentally unhealthy on the whole,
Not to be snarky (ok maybe a little), but they do believe in unprovable beings on some "higher" plane of existence...
If they’re practicing Buddhists they recognize that their own self doesn’t exist, so I think they’re winning compared to the average Westerner who believes in free will. Not to mention all those other unprovable beings like “Moses” and “George Washington” who like to hand down written commandments we follow.
That's true! And it's very likely that meditation is part of that. On the other hand, most people believe in unprovable supernatural beings.
One of the most popular belief systems today posits that incorporeal consciousnesses with names like "California", "Ukraine", and "Google" are the causes of most everyday events, although when you investigate sufficiently you always find that whatever physical doing is attributed to "California" or "Google" is actually done by an ordinary, corporeal human being, like a Scooby-Doo villain. Nevertheless, people adhering to this belief system commonly become very angry when you claim that "Google" exists only in their imaginations.
It is one of the basic tenets of Buddhism† that humans are constantly deluding themselves and doing self-defeating things. In modern terms, you could say they are all mentally ill. This is asserted of humans in general, not just those who meditate a lot.
It's unnecessarily mean if it's not true or, arguably, if there's nothing they can do about it. But if it's true and there's something they can do about it, then not saying it is being unnecessarily mean.
The Buddhist prescription for how to get better (from common garden-variety self-delusion, not schizophrenia) is called the Noble Eightfold Path, and a large dose of meditation occupies an important place in it. Other important ingredients traditionally include material renunciation, strict nonviolence, celibacy, abstinence from alcohol, honesty, politeness, etc. https://en.wikipedia.org/wiki/Noble_Eightfold_Path
