I should have added, if you think you've had a psychotic episode when stoned, STOP SMOKING NOW. If you drink, STOP DRINKING NOW. If you do any other drugs, STOP NOW.
I don't want to sound alarmist, but the very latest research about the so-called 'causative effects' of cannabis...which in my opinion is a very wrong term...has found that people who suffer psychotic episodes when stoned have an anomolly in a particular gene pair linked to your dopamine output. When affected by THC, the cannabinoidal receptors associated with dopamine output open the tap and allow dopamine to flow. Problem is, it can't shut off and the dopamine floods a part of the brain that then initiates a psychotic episode from a dopamine overload. What should also be noted is that it was estimated that only 2% of the smoking population were affected...AND...the research was done on diagnosed schizophrenics, so the research was tilted in that direction anyway.
Note that it is the brain and the dopamine flood, not the weed that causes the attack.
If you have recurring regular negative effects when smoking weed, slow down or stop and let a GP or doctor you trust know what's happened. You can then see if there is an underlying problem that hasn't surfaced prior to smoking (or smoking in extreme amounts). In a small number of cases, cannabis can expose an a previously unknown psychological condition.