Now, I'm just running on memory here, and I'm pretty sure I've said this already - it is possible to induce a state of psychosis by consuming enough thc. You cannot, however, cross that threshold if your method of getting high is smoking or vaporizing the pot; you'll black out well before that happens. But consider cookies or brownies that are made by leaching the thc out of the plant and having it absorb into butter. The thc levels in that butter could be concentrated and higher than anything you'd find in the plant, or even in other forms of concentrate, like hashish or hash oil. Consuming vast quantities of those levels of thc can induce a psychotic state in a person (a cannabis induced psychotic disorder), but it's not referring to a permanent psychosis based on one episode of consuming the drug. On this website, there are two people who can provide anecdotal evidence of what happens when you eat too much thc, but then anecdotal evidence, especially over the internet is questionable.

There is, however, evidence that those who suffer or have latent paranoid schizophrenia are more likely to have a psychotic episode if they use marijuana, and that consistent marijuana use brings forward symptoms of schizophrenia-spectrum disorder. This isn't something that will happen to everybody - just people who have a pre-existing medical condition. A small group of vulnerable individuals. The key distinction with such an episode that gets doctors concerned is the length of time the psychotic episode persists. In most people, it will last a couple hours and eventually fade away with 0 chance of remission. In a small group of vulnerable individuals, the symptoms can persist past a 48 hour mark, but that's more indicitive of larger medical/mental issues in the person in question, and studies haven't really been done in this particular area too much because there are too many variables to control easily.