I don't know that it causes psychosis, but there is certainly enough information out there to suggest that it will hamper any positive effects of medication that you might be taking to manage your bipolar disorder. This is a fairly recent link from Webmd that you might have already read: http://www.webmd.com/mental-health/n...hotic-symptoms

I used to work in a psychiatric hospital; there, I saw a lot of people who had many mental health problems that were significantly complicated by their used of marijuana. Contrary to what the apologists say about this drug, it is not a harmless recreational drug.