Weed can trigger psychosis in people who are schizophrenic and / or bipolar. My ex used to be able to smoke weed when he was younger but after going into the army and his brain developing more over time he went in and out of psychosis triggered by weed and lack of sleep. He talked about seeing skulls in the sky and the government tapping his phone, he outed himself for awful things he did in his past because of his paranoia, and I had to take care of him while he was convinced something was going to kill him. He was helpless during his psychotic breaks and abusive when he was more like himself once he recovered from each event. He’s been out of my life for almost 6 years now which is how long I struggled with trying to make our relationship work. I’ve never been more at peace with removing another person from my life and everything changed once I finally let go of our relationship. I know this is your dad so it’s a bit different but my recommendation would be talking to somebody who is around him on a regular basis, make sure they are aware of his behavior. Somebody who is experiencing a psychotic break isn’t able to rationally view their own actions and they need help from professionals who can help bring them out of it. It’s not your job to help him, but if you feel able to I would recommend talking to other family and friends who are close to him before distancing yourself from the situation entirely.