The ego-dissolving power of psychedelics is something that has always been regarded as a positive, from Leary to McKenna to your average nut on the street (i.e. me). But is it all that great? What if all we are doing is giving our egos exercise in defending itself, making them even stronger in everyday life.
I mean, how many psych users do you know who profess Love and Peace and Acceptance but are in fact neurotic individuals whose egos require coddling just to function?
It's only anecdotal but I can name three.
Well here's the thing. Psychedelics don't change who you are. If you're an egomaniac, psychedelics will further bring that out. Besides that, there are other ego games that even people who are not otherwise egomaniacs will sometimes display. Namely, some psychedelic users (and non-psychedelic users even) develop an ego trip on "enlightenment", and how they have superior knowledge to non-users. You see the same thing in many people who subscribe to "new age" beliefs. As an additional point of comparison to "new age" belief systems, some people who get into psychedelics begin to believe just about anything they experience or even read about that seems to jive with what they want to believe. In this way psychedelics can be damaging for some, because they make you more suggestible.
As for ego death, I feel that my experiences with it, especially my first one, did me nothing but good. It allowed me to completely step outside my individuated perspective for a bit, and upon re-entry, my worldview was changed for the better. It has allowed me to become a more selfless and accepting person. I would say, for me, that I have become less neurotic and more able to see the big picture outside of myself. Of course, I worked towards this. I had a period of being pretty out there, and a period of finding it difficult to live in the culture I grew up in, but I resolved these things and no longer have these issues. One damaging thing I see in a lot of psychedelic users, which I went through too and which I put down to youth and not having had enough time to really integrate the psychedelic experience yet, is this idea that the ego is a bad thing and should be escaped. This is not true, it's in fact nonsense. The ego is simply your sense of self as an individuated life form. The time for the ego to be obliterated permanently is death. Removing it temporarily can result in great insight, but trying to suppress it entirely, or too often, leads to escapism at best. We're here now to live life as an individual; whether or not that individuality is an illusion is irrelevant because we still wake up every day with this perspective and it is our experience.
Regarding drug addiction/mental illness and psychedelics, I think that is a correlation and not a causation. Many people who use psychedelics are the drug experimenter type, and at some point they are bound to tangle with addictive drugs too. And then some, but not all, develop drug problems, just like anyone who tangles with addictive drugs. Personally, I started smoking weed, then tried DXM, then MDMA, and by then I was ready to try just about anything. Psychedelics came next, and then I found opiates. I loved the feeling and so, innocently, I became addicted, slowly but surely. I was in an abusive relationship and as time went on I used opiates to cope with that and my addiction became serious. I was addicted for 10 years but psychedelics had nothing to do with it even though I used them during many periods of this time. Psychedelics (ibogaine) eventually helped me to get off and take my life back. There are about a metric shit ton of people addicted to alcohol or opiates or what have you who have never used or don't currently use psychedelics. There are also some who do use psychedelics. There are lots of people who use just about any drug they can get their hands on. You can't blame psychedelics for drug addiction. It's the same for mental illness. There are loads of people who have never used a psychedelic who have all kinds of mental issues, and there are also people who use psychedelics who have mental issues. There are also plenty of people in both categories who do not have mental issues. Unfortunately mental illness is very prevalent these days, in the whole spectrum of types of people, drug users or not.
Psychedelics have been net positive for me without question, although I have had negative things come from them in the short term. It's been a long road but I'm thankful for them. Psychedelics aren't for everyone, and like any tool, they can be used for good or ill. I know psychedelic users who are well-adjusted and highly functional and happy, and psychedelic users who are the opposite, and varying degrees of in-between. The same as I know non psychedelic users who fit into all the same categories.