Probably something to do with it at least temporarily scrambling your mind, making your body incredibly numb during its effects and at periodic times up to a few months later. There is the potential that your concentration could be reduced, that you are unable to look people straight in the eye because you have seen perceptions that they do not know and that you think that they see these strange perceptions in your eyes.
You do not see fantastic Tim Burton / Dali surrealness. It's just like your perceptions have been slowed down so that it's like you're looking at a picture book animation flickering and you have awful numbness. Of course in such a state your life (and that of anyone near you) could potentially be in some danger, not only from the possibility that your tablet might have been spiked with a more immediately physically harmful drug but from potentially misjudging your surroundings like the speed of moving vehicles. Some people might think that they have put themselves in a more safe place but if a gang of people came up to them they would be potential mincemeat because they wouldn't be able to fight back / run away in proper control.
The problem in trying to convince people not to take them is that some really cleverly creative people have taken them - e.g. The Beatles, Brian Wilson. But consider- thse people were already really creative by the age of 15. Why would you bother messing with that? In those case their creativity MIGHT have been further enhanced for a very short period of time but , come the 1970s, their creativity was becoming a shadow of its former self. That might be coincidence (the 60s were special in general for some artists compared to the 70s) or it might not. And for Brian Wilson LSD, coupled with his sensitive disposition, left him emotionally at sea for a while. It makes a very interesting story in retrospect but, unless you're lucky enough to already be in a world famous band, it's possibly not advisable in terms of securing a full future, unless your idea of that is to be a bit of a recluse which few girls have the patience for.
I would say that it's fairly conclusive that they cause depression and a certain confusion in dealing with other people (mild paranoia maybe) and that could turn lethal if it gives no sense of hope for the future or a sense that, whilst you may be in touch with your intellect, you might have no sense of being in touch with the emotions of anyone but yourself.
Mushrooms are a fungus. We know that some poisionous ones can kill so , unless it's a normal common day one you're buying in Sainsburys, you're dicing with things that are, fairly objectively, not necessarily meant to be consumed in any way.
If you want to have a great imagination immerse yourself in books and films and your own thoughts, not drugs. None of the Monty Python team ever significantly (or at all as far as we know) took drugs. Drugs cause lethargy and, more than highs and lows, they just cause dull flatness. If you want to make a name for yourself being creative, you'll stand more chance if you have the ability to turn up on time and be consistent (as they were- they worked normal 9-5 hours) and alert and clearly outwardly inquisitive (rather than just inwardly inquisitive) because then other people will invest time in you and it will give you confidence and possibilities.
If you've already taken it though don't beat yourself up about it- it's in the past. It doesn't say in the Bible about drugs like these. Maybe there are some positive effects but I don't suggest that it is worth that chance because there are definitely some negative effects. Just do the best with where you are.