Typical Marijuana Side Effects:
These are not typical side effects but mix up common side effects and effects common only in very heavy users.
Enhanced cancer risk
I am sure that there are studies showing that marijuana increases cancer risk, but here's a study showing marijuana decreases cancer risk. http://cancerpreventionresearch.aacrjournals.org/content/2/8/759.abstract
Decrease in testosterone levels and lower sperm counts for men
True in a study of very heavy users
Increase in testosterone levels for women and increased risk of infertility
Possibly true in very heavy users, not well studied
Diminished or extinguished sexual pleasure
Possibly true in very heavy users, more typically users feel increased sexual pressure
My main dispute was that your source for evidence was bad because it confused classes of users. I think you are also confused about this.
The study of psylocybin at Johns Hopkins involved giving middle aged, religious people psylocybin under carefully controlled settings. It is indeed interesting research that they had mainly very positive experiences. I suspect that similar results would have been observed if cannabis extract or THC compounds would have been administered as an alternative in the Johns Hopkins psylocybin study. Remember that the study was only for one time use of a drug in non-drug users.
If the research subjects were instead administered psylocybin twice a week for a year, many of them would go crazy. If marijuana causes damage to the brain, psylocybin causes orders of magnitude more brain damage. Just ask a psylocybin user to multiply two digit numbers and see what happens.
If you are seriously concerned that marijuana will cause permanent brain damage after one use, then it is irrational to think that consuming psylocybin is a good idea.
I am sure that there are studies showing that marijuana increases cancer risk, but here's a study showing marijuana decreases cancer risk.
My guess: marijuana by itself slightly decreases cancer risk, but it's usually smoked together with tobacco, which increases cancer risk to a larger extent.
Human beings are all crazy. And if you tap on our brains just a little, we get so crazy that even other humans notice. Anosognosics are one of my favorite examples of this; people with right-hemisphere damage whose left arms become paralyzed, and who deny that their left arms are paralyzed, coming up with excuses whenever they're asked why they can't move their arms.
A truly wonderful form of brain damage - it disables your ability to notice or accept the brain damage. If you're told outright that your arm is paralyzed, you'll deny it. All the marvelous excuse-generating rationalization faculties of the brain will be mobilized to mask the damage from your own sight. As Yvain summarized:
I find it disturbing that the brain has such a simple macro for absolute denial that it can be invoked as a side effect of paralysis. That a single whack on the brain can both disable a left-side motor function, and disable our ability to recognize or accept the disability. Other forms of brain damage also seem to both cause insanity and disallow recognition of that insanity - for example, when people insist that their friends have been replaced by exact duplicates after damage to face-recognizing areas.
And it really makes you wonder...
...what if we all have some form of brain damage in common, so that none of us notice some simple and obvious fact? As blatant, perhaps, as our left arms being paralyzed? Every time this fact intrudes into our universe, we come up with some ridiculous excuse to dismiss it - as ridiculous as "It's my daughter's arm" - only there's no sane doctor watching to pursue the argument any further. (Would we all come up with the same excuse?)
If the "absolute denial macro" is that simple, and invoked that easily...
Now, suppose you built an AI. You wrote the source code yourself, and so far as you can tell by inspecting the AI's thought processes, it has no equivalent of the "absolute denial macro" - there's no point damage that could inflict on it the equivalent of anosognosia. It has redundant differently-architected systems, defending in depth against cognitive errors. If one system makes a mistake, two others will catch it. The AI has no functionality at all for deliberate rationalization, let alone the doublethink and denial-of-denial that characterizes anosognosics or humans thinking about politics. Inspecting the AI's thought processes seems to show that, in accordance with your design, the AI has no intention to deceive you, and an explicit goal of telling you the truth. And in your experience so far, the AI has been, inhumanly, well-calibrated; the AI has assigned 99% certainty on a couple of hundred occasions, and been wrong exactly twice that you know of.
Arguably, you now have far better reason to trust what the AI says to you, than to trust your own thoughts.
And now the AI tells you that it's 99.9% sure - having seen it with its own cameras, and confirmed from a hundred other sources - even though (it thinks) the human brain is built to invoke the absolute denial macro on it - that...
...what?
What's the craziest thing the AI could tell you, such that you would be willing to believe that the AI was the sane one?
(Some of my own answers appear in the comments.)