I think the vast majority of the research suggests that cannabis (with moderate or higher levels of THC) is a bad idea if you have psychosis / schizophrenia. I think most psychiatrists who are working to help their patients try to get them to quit.
Here is a quote from a current study in Europe:
“Cannabis use by people with schizophrenia is associated with family distress and poor clinical outcomes. Therefore, an Family Motivational Intervention (FMI) was developed to help parents to motivate their child with a diagnoses of recent-onset schizophrenia to reduce cannabis use.”
source:
https://clinicaltrials.gov/ct2/show/NCT01167556?term=schizophrenia&rank=8