Psychedelics can be used accompanying professional depression treatment. It should be said, though, that they are not antidepressants but kind of dissociatives (LSD, mushroom) or “integratives” (my own term with cactus/mescalin). Another thing is MDMA, which is not psychedelic but indeed acts as an antidepressant (all chakra opener, as i call it, but it’s actually borrowing a serotonin flood from the reserves).

The most important thing to tell anyone for safe use, is to know your substance before taking it: dosage and what to expect. Also, start low, as the personal sensitivity can not be known before trying. https://erowid.org is a site which can give a lot of curated information, reports from people etc.
The other thing is to have an intention which might be broad, like “i want to go introspective”. From that comes the important attention to set (one’s mindset and general state at the time) and setting (one wants to be in a comfortable place, be comfortable with the people around if any, probably be outside not in closed rooms, time of the day, moon phase, joice of a sitter or guide, etc).

What i mean by “dissociative” is that it can help set oneself aside from one’s mind and ego/psyche, so as to get to see one’s own functioning/patterns from a distanced POV. Or as @BackOnMyBS already put it, a “more conscious access to one’s brain”. – Given one has the intent of having that. (One can also have the intent to just free oneself for intuitive dancing to trance music with LSD … it’s a tool after all. And the outcome can never be exactly predicted.)

Yes it can be life-changing. Be aware of that, one might get insight in things that other people are just not aware of, and that may not be easy to put in words. After the experience, “integrating” the new discoveries in everyday life is an important part, and having people who can help get a clear mind with that might be a good idea.
My first mushroom trip gave me an idea to what extent my perception of one and the same world can be altered, and how much my perception is being simplified by those filters in the brain which allow us all to go without being overwhelmed by excessive sensory detail – and to what extent other people’s perception of the world could potentially be different from mine.

Then there is this certain entheogenic aspect, especially with the natural stuff (plants, fungi), which after a while made me go a spiritual path. Although i would say there is no such thing as a bad trip, there are certainly challenging experiences possible. Things once seen, can not be made unseen. Psychedelics must be discouraged if there is a possibility of schizophrenia or during episodes of anxiety. It shoud be expected that current states get amplified during the experience, so getting into anxiety loops could teach some due respect. A sitter (an experienced person who is sober and doesn’t interfere) or a trip guide (an experienced person who goes on the trip themselves) is recommended for the un-initiated.

All of the above is for the “psychedelic” dosage which one doesn’t usually want to take very often. There’s another way to take certain substances, that is more like a medication, and that is microdosing. Using 5-10 µg of LSD can help me “be present”, to alleviate me above my psychologic patterns, liberate me from anxiety, and get me in balance psychologically as well as physically. Sensitivity varies from person to person. I did microdose approximately every 3 days for several years now, with occasionally some weeks/months off. My goal was to see if taking it as a medication could help re-wire the brain for good. One finding of mine in that direction is that i had to reduce the dosage over time (it’s easy to notice when i’m “over the top”), and that after a while i often feel no necessity to take it.
So far, i know of one person who i’d say is addicted to “microdosing” LSD (well, they call it MD but they take far too much IMO, and mix with MDMA), yet i would address that to the general patterns and habits of that person rather than to an addictiveness of LSD per se.