There is for example research showing that psychedelics have a lasting effect on the Big 5 personality trait "openness to experience": https://www.psychologytoday.com/us/blog/unique-everybody-els...

Which is quite remarkable given the stability these personality traits usually have.

Overall while it seems to be clear that people who take psychedelics don't become saints spreading love for the rest of their lives, there's some solid evidence accumulated by psychologists that psychedelics have some real effect.