Regarding Nihilism as a Cannabreak symptom. Some dudes in Big Pharma reasoned that since THC enhances appetite, and since THC activates CB1 receptors in the brain, then a CB1 blocker might make a good diet pill. Enter Rimonabant. They started selling it in Europe, there were many reports of weight loss. But then there was trouble, some people got depressed, and they rather suddenly withdrew it, without detailed explanation. In reality for many patients it was blocking ALL perception of pleasure. Ahedonia they call it. Rumor has it there were several hushed up suicides. There ya go, nihilism.