I just turned 50 a few days ago, so it has been more than a decade since I much cared about the topic, so I do not have any sources at my fingertips.
However, at one time, I was Director of Community Life for The TAG Project (TAG = talented and gifted), so I can tell you with confidence that mental issues such as autism, ADHD, and OCD are so common among high IQ individuals that some folks refer to them as comorbidities. The higher the IQ, the more likely you are to see some issue of that sort. That is something you should be able to easily verify with a quick search. If you can't, I can suggest some sources. (I am on a tablet ATM. Providing links would be a pain.)
Some years ago, I was contacted by a woman who had been brutally raped in her teens. She had dissociated during the rape. She felt really bad about that and, over the years, mental health professionals and others had given her messages and attitudes that just reinforced her negative feeling. I told her that it only proved that something was done to her that was really terrible and, unable to physically escape, she did the only thing she could do to protect her mind. I suggested to her that fragmenting some piece of your mind puts it on ice so you have hope of retrieving it later. It isn't lost. You prevent it from being outright destroyed by what you are enduring. So I suspect it probably helps to have a high IQ so you can create complex internal structures if you are in a sufficiently hostile setting, and then the result can be multiple "faces" developing. If it goes on long enough, presumably they can become more distinct than the sense of personaes I experienced.