I think the link has been established between pot and “heightened psychosis” among people who already have psychotic symptoms. I’m not sure it’s been established that pot actually causes psychosis.
Also, I personally would not say pot “causes brain damage” if by brain damage we mean killing brain cells. Alcohol kills brain cells by gluing red blood cells together so that they clump in the capillaries, tear the capillary walls and rupture nearby brain cells in the process.
As far as I have read, pot does not kill brain cells. However the link to short-term memory loss is well established and new studies show the younger the user, the more permanent the effect. I would use the phrase “brain impairment”, not “brain damage”, since to me that second phrase implies destruction of brain cells.
Also, I don’t know what studies there are regarding productivity, but my own non-scientific observation of pot-heads leads me to believe that pot has dramatic negative effects on productivity.
I'm talking about differences in brain structure, as revealed in imaging studies. This article talks about it.
While that article discusses one type of damage, other studies have shown different kinds of damage. For instance, studies have demonstrated durable personality changes (such as the lack of motivation that afflicts pot smokers). And yet others show that pot use in adolescence precipitates psychotic disorder. Here, adolescence refers to the period of time in which the brain is still developing, which occurs up to about age 25. In these studies, there is no way to determine whether the kids who become psychotic were predisposed, were already developing the disease, or got the disease as a result of the pot use.
As this experiment with pot legalization goes on, we will see a lot more impaired people. I'm inclined to think that the old propaganda film, "Reefer Madness" was not as over-the-top as I had always believed. I do not think that pot legalization will continue, as it becomes more and more apparent just how damaging it is and government officials roll back legalization as a result.
I remember a trip to Chuck E Cheese with my kids to a birthday party. the waitress was obviously stoned. She stood around smiling (at nothing) with glassy eyes and didn’t do anything that anyone told her. I am sure she got herself fired because everyone else in the place as bustling around, busy busy.