"Common marijuana psychosis symptoms are paranoid delusions, suspiciousness, and a sense of grandiosity. Other potential symptoms include hallucinations, dissociation or a feeling of detachment and unreality, disorganized and disturbed thoughts, inappropriate emotional responses, and unusual changes in behavior."
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Marijuana works by causing dissociation. This is the high that people enjoy so much. It takes you away from yourself. This is why it can cause some pain relief. So if someone is already suffering from psychosis or mental problems marijuana will make it worse.
The other issue in Thailand is that many people already have magical thinking. They already have strange ideas that do not follow logic. Superstition, religious idealism.
So people making fun of the story i think are wrong. And this is typical of addicts, they are deluded about the true effects of the drug they are on.