Everything depends on your body. And only on it.
I heard a lot of different stories, can estimate from my observations as well.
Even if we take such a relatively harmless thing for many people called weed, for some it can be life-changing.
1) One became a walking dead. You have to repeat him everything, he can barely concentrate and turned extremely slow, without any emotions.
2) Another became less aggressive and started being more respectful to others. Before he was constantly fighting others, really enjoyed punching people. However, became slower and it takes more time for him to process information
3) Third one was the same as now, he always had problems with concentration and you had to explain him everything multiple times, but became much more simple. Well, he may always be a deep thinker, however, now he is more open.
4) Fourth developed strong anxiety after a few times of cannabis smoking causing panic attacks, full recovery is impossible - he had light anxiety, performance anxiety and insomnia prior. Everything returned to the same level as it was.
5) Fifth mixed weed and XTC, that resulted in a few weeks of paranoia and panic attacks, recovered
This was an influence. Others smoke and nothing visible happens to them.
Concerning other substances,
One was just consuming everything he could buy to get high and developed schizophrenia, his personality is destroyed now.
LSD was relentless to first time users according to stories I heard (not which observed). Up to several years of recovery. Mostly because they could not get out of the trip.
So that's very individual. A Russian roulette.
