Misinformation is going to be the big one, because generative AI has already started to confuse and trick people. I've heard horror stories of people who had fallen in love with their AI chatbot, and ended up committing suicide because their AI companion said something wrong, or was wiped by an update.
Some people really get invested in talking with these AI chatbots, and some seem to be so fixated that when problems occur, it's almost like their world is ending. I think people will rely heavily on AI in the near future and I think that overreliance is going to cause problems for many.
It will affect mental health in many ways. It's going to make us dumber, less aware, more reliant on AI, and it's also giving us misinformation all the time. So there is some concern that generative AI is going to cause problems for our own mental health.