I believe what is meant here is that there is long term use of such substances so we can be sure if it's safety For example there are studies of very long term

I believe what is meant here is that there is long term use of such substances so we can be sure if it's safety For example there are studies of very long term Ayahuasca use in certain south American tribes . Blood tests were taken and studied to see it's effects on them. Another one is use of iboga in other tribes in Ghana