Anyone who uses pot, or has used pot, just pot by itself with no other stimulant, will tell you all it makes you is mellow, chills you out and provides a lovely wash of body relaxation and a gentle mental uplift.
And occasionally it makes people paranoid, hallucinating and psychotic. Just because you like the buzz does not mean that it can't have negative effects on others who use it.
No one can overdose from pot.
In a strict pharmacological sense, that is pretty much true, certainly if the intake route is limited to smoking or eating product produced with the herb itself rather than concentrates. So far, potheads have had the good sense of not ingesting entire bottles of the highly concentrated (30-50%) THC extracts used to make edibles. We'll find out once one of them ingests a couple of grams of THC whether the 'no one can overdose from pot' mantra holds true.
Plenty of people have hurt themselves and others in recent years trying to extract THC in home-labs using Butane in a open-loop system. At times, 1/2 the burn unit at UC davis is filled with BHO producers. Then you have the surge of hospital admissions of kids in the western states who got their hands on the wrong kind of brownies. The thing with THC induced psychosis is that none of the usual anti-psychotics seem to touch it. You just have to keep them from hurting themselves for however long it takes to wash out of the system. Since 1999, the percentage of drivers in fatal collisions who had cannabinoids in the drug-screen doubled from 6.1% to 12.3% (still some way to catch up to the 40% with alcohol) and for some reason most of the young men who died after they fought with the police in the recent well publicized incidents had cannabis in their system.
But no, its completely harmless. It only makes you happy, happy, happy and maybe hungry. Right ?