I don’t know but a lot of people do not rate Meditation too highly. I do believe it has tremendous capacity to limit the symptoms and eventually cure Psychosis.
The research in this field is very limited and could be business related (The Pharma companies do not want people to be recovered by Meditation).
The Meditation I recommend is Vipassana/Buddhist/Awareness/Choiceless Awareness/Insight Meditation techniques taught by Buddhism, Osho , J Krishnamurthi among others. This meditation has scientific data that it definitely increases the:
a. Grey matter in the brain.
b. Increases general awareness
c. Increases intelligence.
I think Meditation should definitely be promoted more.