I'm a psychiatrist who works with lots of people who are homeless and mentally ill. My experience faces a strong selection bias in that I don't see the homeless people who don't have marked symptoms of mental illness. The ones who come to my attention usually have delusions and hallucinations. Beyond anecdotes, there's some reasonable and ongoing research on the topic.
Methamphetamine remains far more strongly associated with psychosis than cannabis, but both anecdotes and research support that THC extracts are considerably more likely to cause psychosis than whole flowers. There also seems to be something protective about CBD, so THC extract (dabs/oil) products appear to carry more risk due to both their high THC content and the absence of CBD. People who use cannabis heavily in adolescence also have an increased risk of developing a psychotic disorder.
Methamphetamine remains far more strongly associated with psychosis than cannabis, but both anecdotes and research support that THC extracts are considerably more likely to cause psychosis than whole flowers. There also seems to be something protective about CBD, so THC extract (dabs/oil) products appear to carry more risk due to both their high THC content and the absence of CBD. People who use cannabis heavily in adolescence also have an increased risk of developing a psychotic disorder.