Medical science and the government are now saying, once again. That cannabis cause's Schizophrenia. After 40 years of smoking it I can say it does cause some paranoia in some people. It depends on the quality of the weed. And who you are with and the mood your in. If your stressed it can make you paranoid. Lot's of people will disagree with me but i bet they are young people. If you go to a country like Iran were weed has been smoked for centuries you will notice it is smoked in moderation. They know the effect of over use. But people in the uk tend to binge on it and smoke it like they would fags. Like anything in excess it becomes a poison. Too much of anything will have a bad effect on you. And that is the problem with young people who smoke weed. They tend to overdo it. This is probably why there is an increase in the psychological problems now showing. So my message is smoke it sensibly and don't get out of your face.