Ayahuasca, in particular, has the potential to be a powerful tool in treating severe forms of depression, drug addiction and PTSD
Not more powerful than getting a pet or making some good friends. Medication starts being medication when it surpasses the placebo threshold which is around 33%. Unfortunately, no research on LSD can demonstrated anything beyond that.
I have to point out here that research on the subject is limited due to bias in regards to these drugs. Nonetheless, nothing of significance has be shown. Another interesting part is that modern medication for depression are not any better and might cause even more problems than simple drugs such as Ayahuasca.
It's misleading to say that "nothing of significance" has been shown.
There were more than 1,000 peer-reviewed clinical papers detailing the use of psychedelic compounds (administered to approximately 40,000 patients) published by the mid-1960s.
LSD was seen to have a greater than 50% success rate in treating alcoholics in just a single-session:
Source: Smart RG, Storm T (March 1964). "The Efficacy of LSD in the Treatment of Alcoholism" (PDF). Quarterly Journal of Studies on Alcohol. 25: 333.
In addition, there are studies ongoing today: https://www.nytimes.com/2014/03/04/health/lsd-reconsidered-for-therapy.html
The founder of Alcoholics Anonymous, Bill Wilson said that, "I am certain that the LSD experiment has helped me very much. I find myself with a heightened color perception and an appreciation of beauty almost destroyed by my years of depression.”
This is just one use of LSD.
Maybe you will enjoy this TED Talk by a current research scientist:
that's like giving weed to tobacco smokers and claiming that it cures puffing.
Since nicotine addiction often is a self-medication for repressed trauma, weed might treat the underlying anxiety and stop the person smoking tobacco.
However, I think LSD would be more effective than weed for nicotine addiction.
Scientists have found that LSD will cure a person of tobacco addiction: http://www.newsweek.com/how-acid-helped-stop-smoking-413593
And other psychedelics are also effective at treating tobacco addiction:
http://www.bbc.com/future/story/20150615-could-psychedelic-drugs-make-smokers-quit
And:
https://www.theatlantic.com/health/archive/2016/06/live-like-youre-on-mushrooms/487286/
pets can cure tobacco addiction. exercise can do that as well.
addiction is not a substance problem. Is a human connection problem.